CeC technical information?
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Category: The Garage
Forum Name: AMC 6 Cylinder Engine Repair and Modifications
Forum Description: AMC-made I-6 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: https://theamcforum.com/forum/forum_posts.asp?TID=99727
Printed Date: Mar/28/2024 at 6:41pm Software Version: Web Wiz Forums 12.03 - http://www.webwizforums.com
Topic: CeC technical information?
Posted By: MIPS
Subject: CeC technical information?
Date Posted: Apr/27/2019 at 1:55pm
Has anyone ever spent time reverse engineering how the 6-cylinder CeC was built or any technical documents for the computer? They seem to be in the realm of "unserviceable if bad" due to how they are potted or at least, I'll have to destroy a computer to find out on my own.
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Replies:
Posted By: Trader
Date Posted: Apr/28/2019 at 4:01pm
Have not reverse engineered but sometimes they can be "repaired" if it's moisture from cracked or separated epoxy. Just clean the unit, wire brush the case and epoxy edges, flush with WD40, put in an oven for 2 to 3 hours at 160 degrees, and then pool in more epoxy. Works some times, and if it does work the unit will last for years of service.
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Posted By: MIPS
Date Posted: Apr/28/2019 at 8:32pm
Oh, mine works. I'm just more curious exactly how it was constructed and how a modern replacement could be provisioned. I've basically finished with the electrical and operational theory for all the sensors but now it's cracking the computer itself open to determine what type of microprocessor they used (and where it loads its ROM from), how the interface buffering works and if there are any other secrets hiding in the potting, which no matter what way you do it will be a destructive ordeal and will require a sacrificial unit. People who are both skilled in automobile mechanics and electrical engineering isn't common.
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Posted By: farna
Date Posted: Apr/29/2019 at 6:23am
Well, it's a GM system, so you might find some info on GM sites. Most people abandon it if it stops working, going back with a non-computer carb and distributor. Many forget that the distributor is part of the equation and use the original. That will work, but you really need a non-computer dizzy for best engine operation since it is calibrated differently.
------------- Frank Swygert
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Posted By: tomj
Date Posted: Apr/29/2019 at 10:19pm
i've made a lot of software-driven electronics for car control, including a completely software-driven cooling system (no belt-driven pump, no thermostat). i have no idea what CEC is beyond feedback carb, but i can tell you what the replacement *electronics* would be -- a modern microprocessor, a few MOSFETs, and a half dozen glue components. times have changed.
all functionality of any kind is done in code. LONG GONE is doing *function* in electronics. it's too brittle, costly, inflexible. purpose-written code is flashed into nearly generic hardware. my car has three computers, networked, that do various things, and the hardware for each is exactly the same (except one has adds a big LCD, SDcard, controls, etc).
here's my cooling system. i do highly reliable electronics in an automobile environment. the devil's in the details.
auto electronics from the 80's or even 90's is so fantastically backwards and barbaric from what can be done today, there's no contest. it's like comparing a 2018 Corvette to a Model T.
code and electronics: https://sr-ix.com/Code/index.html" rel="nofollow - https://sr-ix.com/Code/index.html the electronics itself: https://sr-ix.com/Code/Electronics/index.html" rel="nofollow - https://sr-ix.com/Code/Electronics/index.html closed-loop cooling: https://sr-ix.com/Code/roadsterCooling/index.html" rel="nofollow - https://sr-ix.com/Code/roadsterCooling/index.html
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: tomj
Date Posted: Apr/29/2019 at 10:48pm
btw, the best place currently to find nifty controller and electronic stuff these days is Adafruit http://adafruit.com" rel="nofollow - http://adafruit.com . run by Lady Ada, aka Limor Fried, really good designs, good prices, lots of information, free software, drivers for everything. i love everything they do there.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: Greyhounds_AMX
Date Posted: Apr/30/2019 at 12:05pm
Sometimes you can remove the potting gump by boiling the item in a pot of water. You still have to do alot of scraping though....
------------- 1968 AMX 390 w/T5
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Posted By: MIPS
Date Posted: Apr/30/2019 at 9:03pm
You're pretty much doing exactly what I have in my head, just with a lot more complexity, which is fine as you've done quite a few more things beyond adapt a new computer to an existing system. Your whole site was well worth the read.
I could sit down and pretty easily build a shield for the CeC in an evening. It's like, six 12V digital inputs, four digital outputs, a two phase stepper motor output and an analog 1V O2 sensor input. Without fully understanding yet how quickly the CeC performs the feedback loop you could in theory use a microcontroller as small as the Arduino Pro Mini, which is about the size of a person's thumb, to replace the entire computer, assuming your code fit in the 32Kbyte flash memory.
I suspect that unless GM or AMC at the time was paying for custom semiconductors, the CeC uses something to the tune of an Intel MCS-48 or MCS-51 microcontroller.
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Posted By: tomj
Date Posted: Apr/30/2019 at 10:32pm
i suspect you're right. GM used a slightly-custom 6811 in the "TBI" systems everyone (used to) adapt. dunno what quantity you'd have to order to get custom silicon. Motorola (used to) offer limited OEM quantity semi-custom in 10,000 to 100,000 unit quantities but that was the 1980's. today 100 MHz is no big deal!
so carbs lasted 90 years, then from around 1980 through say 2000 there were "feedback" carbs, electronic/mechanical/hybrid FI, throttle body FI, etc. by ~ 2000 it's port injection and now, direct injection. that stuff in the middle is mostly awful, like "microminiature" electron tubes like Nuvistors, 12V plate tubes for car radios, thickfilm, cordwood, all that awful electronic crap from the 50's and 60's before monolithic silicon. mostly feedback carbs and mechanical FI are horrid curiousities for restorers....
but personally i considered an electronically controlled computer -- for performance and fun-to-make purposes -- might be interesting and practical. the problem is that th base part itself is just to crappy to work with. some crap old smog 2bbl isn't a good basis for anything.
as far as i got was thinking about ... so what would be worth closed-loop control? to me, it would be main jet tuning and altitude compensation (which are really the same thing). analogous to the GM TBI map system, look for errors in the "map" (load vs rpm) lean/rich, and a table to tweak the mix by pulling the control rod up or down. but since this is a stepper with a cntrol rod, it wouldn't be a realtime adjustment like TBI map, but a slow (60 sec? 5 min?) scale that worries more about steady state cruise, and ensure rich enough during high load.
i've considered writing my own EFI -- because it's fun, not because i think i could do better than say MEgasquirt -- but it's a looooot of code for little benefit.
OH MAN! Megasquirt these days is handling X-tau now! that's the phenomenon of what happens when you squirt gas into a runner -- most of it goes down the hole with the air, but some of that wets the runner walls and valve, and that wetted-out fuel then evaporates with a time constant that depends on temperature and other factors.
a feedback carb compared to current Megasquirt (never mind what additional magic OEMs do now) is like a stone age club compared to an airplane.
for me, it's a carburetor, a nice "simple" (right!) mechanical thing, or full-tilt-boogie software, eg. Megasquirt. and this is probably my last carburetor.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: amcfool1
Date Posted: Apr/30/2019 at 10:38pm
hi, just fyi, the early units may be GM sourced, but the 84+ units are FORD, and are still available at any auto parts place, about $200. or so. biggest difference is the early ones control carb only, 84+ control carb AND timing. thanks, gz
------------- george z
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Posted By: MIPS
Date Posted: May/02/2019 at 6:57pm
You are not wrong there. From the mechanics manual alone there's indication of at least four revisions of the CeC before the Eagle went to TBI and a completely different arrangement. First revision CeC (with DTC and CHECK ENGINE circuit) Second Revision CeC (without DTC and CHECK ENGINE circuit, due to CPU constraints) Third revision CeC (the "C4" system) Fouth Revision CeC (Ford ECU?)
The ultimate goal is a drop-in replacement to the CeC that keeps the car compliant with regional emissions testing and otherwise identical performance while being made of modern components, however the added bias control of the fuel mix and ignition advance to work around the major shortfalls to the original CeC's locked-in emissions limitations. No fancy displays, no new wiring, no complicated instructions. Just plug it in, tweak a knob or two while tuning to your desired spec and you're set. System diagnostics otherwise remains the same.
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Posted By: tomj
Date Posted: May/03/2019 at 1:24am
MIPS wrote:
The ultimate goal is a drop-in replacement to the CeC that keeps the car compliant with regional emissions testing and otherwise identical performance while being made of modern components, however the added bias control of the fuel mix and ignition advance to work around the major shortfalls to the original CeC's locked-in emissions limitations. |
OH. i musta missed that.
in that case, since you have a good one now, don't take it apart! use it as the standard and measure what it *does*. watch, in real time, what a critical output does in response to an input. THAT is what is important.
characterization. my guess is, it will be hard to get started, to figure out how to look at. off the top of my head, with an oscilloscope figure out what the inputs and outputs look like, electrically -- 12V PWM stepper? analog input? pulses? voltage levels and speeds and pulse widths, not meaning or intent. chances are this stuff will be relatively easy.
install a good wideband O2 sensor, kludge up an Arduino or two to sense (A to D, or code to parse PWM on time (you could probably do 1% by taking a 12V stepper output, passing it through an R C low pass network (integrator) then reading the resulting voltage via Arduino analog in. the delta will be important, not so much precision. *when* does it enrich the carb?
also you probably "know" spark control will be a simple 2D map; load (vacuum) and rpm. no real need to worry about the electronics there, just work out what the map is. that's easy! pull the vacuum hose (or fool CeC with a MightyVac), measure spark advance wiht a timing light at 500, 1000, 1500, ... 4000 rpm with no vacuum (that's "mechanical" advance) then at say 500 rpm, use the mightyvac to vary "load" and measure advance at 100, 90, 80, .... 0 KPa. then simply extrapolate in a spreadsheet. that's how i first populated my Megajolt box the first time, reading distributor with hose off etc.
carb will be slighly harder, but once you get into it probably doable.
get one od Afafruit's boards with built-in SDcard, and write a datalogger that outputs "columns" in CSV format. that's what my datalogger does and it's easy to do a rough job for your debugging.
document CeC's *functions*, it's guts are uninteresting.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: amcfool1
Date Posted: May/03/2019 at 10:56pm
hi, if you need one to take apart, I have an old 82 that's all there, though the aluminum case is corroded some. Don't know if it still "works", though it should, as it hasn't been in use for the whole time I had the car (82 Eagle), since I did the MC2150/HEI thing. It just sat there for over 20 years. Yours free if you want, just give me a couple bucks for shipping, (from 24017). thanks, gz
------------- george z
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Posted By: MIPS
Date Posted: May/04/2019 at 11:51pm
my guess is, it will be hard to get started, to figure out how to look at. off the top of my head, with an oscilloscope figure out what the inputs and outputs look like, electrically -- 12V PWM stepper? analog input? pulses? voltage levels and speeds and pulse widths, not meaning or intent. chances are this stuff will be relatively easy. |
It's so simple. AMC in the process of making it cheap to impliment made all of the sensors extremely easy to monitor and troubleshoot.
With the exception of the O2 sensor which operates within an analog 0v-1v range the entire system is 12v digital and every sensor is either on at 12v or "off" and tied to ground. No pulses, no protocols and no weird switching states. AMC's own documentation is quite comprehensive in how each of the different open loop system states are created before the engine finally qualifies for closed-loop. The stepper motor is a simple two-phase circuit.
On top of the original tool that OTC sold for diagnosing the electronic feedback system I've been developing my own unit that allows for more status information to be displayed at once than the official tool allows. This is basically what I am using to verify AMC's own documentation and hardware before committing further.
if you need one to take apart, I have an old 82 that's all there, though the aluminum case is corroded some. Don't know if it still "works", though it should, as it hasn't been in use for the whole time I had the car |
That's fine. I'll send you a PM.
Ultimately depotting can start either by milling off the aluminum frame to release the epoxy block or skip that step entirely and boil the epoxy until it softens. (see https://www.youtube.com/watch?v=OiPe6f4Oh8E ) Ultimately if that fails then it goes under the CNC machine and the resin is milled off layer by layer until it's thin enough that the rigid epoxy can be again boiled and pried off.
Part of the goal if AMC/GM handled the CeC's ROM correctly is that if it (the ROM) can be extracted from the CeC, dumped and then the original timings and fuel tables extracted from the disassembled code they would not have to be redeveloped from scratch which is where my shortcomings in software development show but up to that point, hardware development is my specialty. ;)
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Posted By: Greyhounds_AMX
Date Posted: May/05/2019 at 4:19pm
How about replacing it with a Speeduino? That would give alot of flexibility. Not sure about running the stepper though.
I suppose with Speeduino it would be easier to switch to TBI.
------------- 1968 AMX 390 w/T5
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Posted By: tomj
Date Posted: May/05/2019 at 9:55pm
WOW! haha yeah that's a lot of good information. good old TSMs! realistically you should assume that there are variations from the TSM, i mean what electronic product doesn't require tweaking in production etc? but its probably a good start.
you could code from what you;ve got there.
what exactly is the point of depotting? i seriously doubt you'll get very much insight into how it works.
nice test box! yeah, you gotta make something that lasts to persist at it. nice job.
O2 sensors are tricky sensors they're anything but linear. the so-called wideband sensors are a lot more proportional and can be made linear with processing. lambda sensors have a super-sharp slope around stoich and so most systems have an abstraction that essentally calculates the ratio of "too lean" to "too rich" time, with L/R flipping back and forth rapidly (GM TBI does this) then using that ratio as "A/F ratio". it's not really possible to control mixture so that the sensor outputs 0.45V. nothing in engine operation is that time-stable (Variable speed, variable load, etc).
that prose description and the pinouts/signals is great information!
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: MIPS
Date Posted: May/07/2019 at 8:50pm
How about replacing it with a Speeduino? That would give alot of flexibility. Not sure about running the stepper though |
I did look it as a potential replacement initially but the problem I found was that it's really reliant on several additional sensors an Eagle traditionally does not have and I wasn't interested in a replacement that also required multiple existing sensors be replaced or upgraded. It's also way more powerful than what an Eagle needs with a stock system. Remember that the more complicated the replacement is to install, the less people are interested in committing rather than just doing a full bypass. Building a replacement does involve starting from scratch but the digital input and output nature of the CeC coupled with relatively low sample rates makes it WAY easier to duplicate compared to even first generation TBI computers.
what exactly is the point of depotting? i seriously doubt you'll get very much insight into how it works. |
Depotting helps identify the microprocessor used, the location of the calibration ROM (which may prove helpful for when creating the same calibration data on the Arduino so you are not making wild guesses) and identify the location of any components that are known to fail with age (lytic can capacitors for ripple smoothing or AC decoupling) or input and output buffers that may be easily or accidentally blown. Computer replacements are costly if your region mandates it be working. If it's built from relatively common parts and we can map out the location of the various circuits then repairs may be as easy as someone ball milling out a chip and soldering in a replacement. Think like how some guilty folks in the 80's and 90's piggybacked new EPROMs into their VideoCipher satellite descramblers. It also verifies that there is no other "secret" connections going on. Note on the diagram above the CeC connector has four unmarked pins. What do they do? Where do they go?
O2 sensors for the 82 year Eagle are compatible with the NTK 23552. It's one of the few parts in the CeC that MUST be replaced as per its recommend 30000 to 50000 miles, otherwise the computer enters closed loop and cannot accurately regulate the mixture. This is also your only time in which you can justify having the emissions maintenance timer installed.
Really I'm just bored right now. I need something to keep my mind busy and this could keep me going for the rest of the year.
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Posted By: MIPS
Date Posted: May/25/2019 at 8:09pm
Well this is a pleasant surprise.
So the silica-mixed resin used to pot the CeC turns into a sticky wet sand when boiled, however makes removing it a billion times easier. Beneath it all has so far uncovered an Intel 8049 8-bit Microcontroller which was introduced in 1976 and discontinued in the early 2000's
The datasheet for this microcontroller can be found here - https://www.ceibo.com/eng/datasheets/Intel-8048-8049-8050-plcc-dip.pdf
The 8049 specifically is the same microcontroller as the 8048, however with 2kb of onboard ROM and more ram, so the precious calibration data is hidden in the chip, but because many hundreds of thousands of products used the microcontroller well into the 21st century the procedure to dump it is well known. I'll keep working away at the resin and see if I can free the board from the body.
Edited: Pretty much done.
Even simpler than I expected. Microcontroller, what looks to be two drivers, a regulator and some other IC I've not really investigated yet. No drivers and no buffers, just a lot of diodes and resistors. I'm going to bed.
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Posted By: tomj
Date Posted: May/26/2019 at 7:43pm
nice work! lol. i still sort-of remember the 8051 instruction set from ye olden dayes. ugh! lol. but that's good depotting!
of course the code is key to the realm...
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: FSJunkie
Date Posted: May/27/2019 at 1:50am
Really awesome to see this.
I wonder what the 1984 and up ECU looks like inside and what processor it uses.
MY father built Apple IIE computers in the 1980's when he lived in the San Francisco bay area and still has his PROM burner, so I figure he could help me out if my ECU ever takes a dump.
1984 and up ECU is definitely made by Ford, though as I understand it, no vehicles other than AMC ever used it.
I suspect the folks over at the Eagle's Den forum know more about this than most folks here. Eagle people are like their own community within the AMC community. It makes sense too, since Eagles are their own unique realm of AMC. They're just different enough from all other AMC cars to make them their own thing.
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited
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Posted By: MIPS
Date Posted: May/27/2019 at 7:06pm
I might very well relocate this discussion over there now that it seems my posting issues there have been resolved, if nobody minds. I'm quite aware that this forum is centered a lot more around the earlier model cars so it might be odd to bump this from time to time with new updates. I'll keep you all informed.
Research I've found about the 8049 is that dumping it is fairly trivial using relatively modern and low cost EPROM burners/readers as Intel even describes the procedure in one of their technical databooks. On top of that for the REALLY savvy you can not only disassemble that original initialization data and modify the fuel tables but if you write it back to an EPROM the 8049 supports disabling the onboard ROM and loading from an external chip, so in all realms of possibility it now makes "chipping" the CeC possible, for at least the 82 model year.
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Posted By: FSJunkie
Date Posted: May/27/2019 at 11:14pm
What did you boil the potting material in to soften it up?
Is the 8049 soldered to the board?
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited
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Posted By: MIPS
Date Posted: May/27/2019 at 11:24pm
Boiled in regular tap water. The IC's have a "not in use" storage temperature that goes up to 150c, so boiling water won't damage them and the plastics in the connector require a lot more heat as well before they start to deform. Initially nothing was in sockets, which makes sense as that adds points for poor contact. For testing and other purposes however I've since changed that.
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Posted By: farna
Date Posted: May/28/2019 at 6:17am
Please do make updates! While you're working on this thing, it would be nice to work around the carb stepper motor. That's the one thing that will freeze up and isn't easily replaced. Sort of makes the CEC useless though, so I'm not sure if there would be a point if the carb can't be controlled. Controlling A/F ratio is the main function, though it obviously controls some of the other emissions stuff, like those three solenoids. I'd have to look at the wiring diagram again, but doesn't it do something with the distributor as well? I've always told people who were (and could legally) removing the emissions to get a non-emissions distributor as well. There might be some merit in making a CEC unit that works with a replacement non-stepper carb like a Weber 32/36 or 38, or Motorcraft 2100.
The Eagles is "it's own thing" because AMC got it classified as a truck, or rather a utility vehicle (which had the same looser emissions as a truck -- looser than a regular car/passenger vehicle). The first primarily passenger vehicle to be so classified by the US Government. Chrysler got the Dodge Magnum wagon classified the same way, though I think that was cheating. The Eagle at least had a truck-like 4x4 system (well, CJ like.. which IS a utility vahicle) and was unique, not just a high power station wagon.
------------- Frank Swygert
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Posted By: MIPS
Date Posted: May/28/2019 at 10:36pm
For the 82 model the computer doesn't actually have any control over the distributor directly. All it receives is the tach pulse (generated by the hall effect circuit in the distributor base) which is used all over the engine and can only send back the ability to slightly retard the spark using the DuraSpark II. The only other control one has over the distributor is the internal centrifugal advance and the vacuum advance, the latter operating from manifold and then ported vacuum as the engine warms up and the CTO switches over but regardless not maintained by the computer. I can also confirm that for stuff like the Air Injection system vehicles that sold without it seemingly will not suffer with it missing (in theory). Mine left the dealer without it at least.
The stepper motor is known as a two-phase stepper motor. It has a permanent magnet and two separate windings. From what I've seen the only other way it can fail besides an open winding is the rack the actuator moves in and out with will gum up. Resistance on this will cause "mis-steps" or simply seize the actuator completely.
The stepper motor is held together with three press pins cut flush with the metal body near the back. As I only have one stepper motor I'm not willing to drill the pins out and better investigate how the stepper motor goes together, however I can only assume that a spray of Electrosolve contact cleaner, a compressed air dry out and then getting some sewing machine oil down into to body through the gap around the actuator shaft (and then carefully pulling the shaft in and out by the rod AND NOT THE PHENOLIC DISC THEN PINS ARE ATTACHED WITH) should clean and relubricate the rack.
Finally I have completed mapping both sides of the circuit board. It seems for the most part the backside is where most of the work happens and on the topside the majority of the board is clad with copper for shielding. I have not yet gone further and compiled things such as a Bill of Materials or logical description of each circuit. That would take weeks.
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Posted By: FSJunkie
Date Posted: May/29/2019 at 2:29am
The 1984 and up system is different, mainly in how it controls the ignition timing.
With the 1984 and up system, the signal pulses from the distributor pickup coil must pass through the ECU before they reach the Duraspark module to trigger a spark. The ECU has full control of the ignition timing.
The ECU continuously monitors the knock sensor and the pulses from the ignition coil indicating a spark plug firing for a power stroke on a cylinder. If the knock sensor detects knock, the ECU waits five pulses then delays the timing of the sixth because that would be the pulse to fire the spark plug of the cylinder that knocked previously. If the knock sensor does not detect knock, the ECU waits five pulses then advances the timing of the sixth. In this way, the ECU continuously maintains the ignition timing for that cylinder right on the edge of knock at all times and under all operating conditions. The ECU performs this function for each cylinder individually so each cylinder runs at it's own unique optimum ignition timing. It has no idea which cylinder is number one. All it knows is an ignition pulse is occurring and whether or not knock is happening as it occurs. Based on that, it determines whether to advance or retard the sixth pulse after that, being the pulse for the original cylinder.
It's genius. It provides more optimum ignition timing that possible with a conventional distributor which runs all cylinders at the same ignition timing, regardless of individual cylinder operating differences (like fuel mixture). It can maintain the optimum ignition timing regardless of ambient operating conditions, unlike a conventional distributor which must be set to a "compromise" setting to run acceptably in all weather and conditions. This system gives better power and fuel economy than possible with a conventional distributor.
And it works. I've watched the ignition primary pattern on an oscilloscope as I tap on the intake manifold near the knock sensor with a small hammer. The tapping will make individual firing lines retard (whichever cylinder was firing during the tapping), but they advance back as soon as I stop tapping and "balance out" to the others.
I drove my Eagle to Phoenix a couple weeks ago with the base ignition timing still set to the more advanced "high altitude" setting. As I pulled up onto the freeway, I heard the engine knock a little. Just for a second. Then I heard the nock slowly fade away as the ECU retarded the timing for the cylinder(s) that were knocking. It did not knock the entire rest of the day. The ECU learned.
It's incredible technology. And people just remove it and throw it away as "emission control BS junk." They just don't understand, or want to understand.
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited
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Posted By: amcfool1
Date Posted: May/29/2019 at 5:57am
hey, fsjunkie, excellent explanation, thank you. When I rebuilt my 84 I decided to challenge myself and go all stock, which I did, and the car is now running well. I did buy a new (remanufactured ) computer, and as many of the sensors as I could. Took some doing, but of the eight sensors, 6 are still available new, mostly thanks to CA and their pollution laws. Only the knock sensor, and I believe the air temp sensor in the air cleaner are no longer available (afaik) The only system I did not rebuild was the air injection system, as mine was totally beyond salvage, so I went with a modern freeflow cat that does not require it. thanks, gz
------------- george z
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Posted By: amcfool1
Date Posted: May/29/2019 at 6:08am
btw, people get rid of this stuff because it is very hard (for the average shade tree mechanic) to diagnose and repair, and one small vac leak can cause all sorts of problems. Just finding parts can be difficult, took me the better part of a year. So don't be too hard on 'em. Better to save an Eagle without the CeC, than just junk the car! What I would like, from the electronic geniuses among us :) , is a diagnostic tool, not a better computer. thanks again, gz (the original AMC code reader is primitive, absolutely unobtainable)
------------- george z
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Posted By: Greyhounds_AMX
Date Posted: May/30/2019 at 7:02am
The computer appears to be the Ford "MCU", which is their first feedback computer. It was out just before they started using the EEC, around 1981.
Here's a 1981 F150 pic:
And if that's the case you may be interested in this for $2 on ebay right now:
------------- 1968 AMX 390 w/T5
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Posted By: tomj
Date Posted: May/30/2019 at 9:32pm
nice work in here!
i'd love to hear what the code does, specifically whart the approach is to maintaining AFR. is there a load/RPM map? (does CEC have a manifold pressure sensor?)
the old lambda O2 sensor only generates lean/rich information, so GM put a closed loop around it all and generated correction by integrating the "error". the point is, the GM system was too slow to correct A/F ratio in real time, in that it first sets fuel (PWM in the GM TBI system, jet rod position with CEC) from history, then adjusted the fuel to correct any error.
the GM TBI system used a custom 6810 or 6801 processor, more computational poop than the lowly 8049. also changing PWM a dozen times/sec is "real time" enough; a stepper motor on a rod in a jet (i think the BBD uses) is slooow...
the problem is interesting to me. i'd love to see the code if you extract it.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: 73Gremlin401
Date Posted: May/31/2019 at 12:20am
amcfool1 wrote:
hey, fsjunkie, excellent explanation, thank you. When I rebuilt my 84 I decided to challenge myself and go all stock, which I did, and the car is now running well. I did buy a new (remanufactured ) computer, and as many of the sensors as I could. Took some doing, but of the eight sensors, 6 are still available new, mostly thanks to CA and their pollution laws. Only the knock sensor, and I believe the air temp sensor in the air cleaner are no longer available (afaik) The only system I did not rebuild was the air injection system, as mine was totally beyond salvage, so I went with a modern freeflow cat that does not require it.thanks, gz |
I'm very much like you - my 80 Concord has everything still in place, but when I got the car, nearly every vacuum tube was either disconnected, leaking, or connected to the wrong things - and the motor barely ran. It's taken some time (the better part of 2 years, fiddling with it on and off) but I've finally got all the vacuum tubes hooked up correctly, sealed, the air pump and 02 sensor replaced (the only failed parts) and the car runs astonishingly well. It was a fun project that really didn't cost much other than time to sort out, and since I live in an emissions-tested area, it was essential to get right.
------------- 73 Gremlin 401/5-spd. 77 Matador Wagon 360/727. 81 Jeep J10 LWB 360/4-spd 83 Concord DL 4-dr 258/auto
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Posted By: tomj
Date Posted: May/31/2019 at 9:18pm
i had similar experience with a 1975 California V8 Gremlin. buckets of hoses. expensive EGR with CA-only pintle. once done though ran just great.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: MIPS
Date Posted: May/31/2019 at 11:38pm
It was mentioned before that these computers were built by ford for AMC, so it's not too much of a surprise to see that unit living in an F150, however if Wikipedia is to be correct, they are not compatible, at least, programming wise. I'll work on getting the chip dumped soon but the adapter is a little expensive and likely take at least a month to show up. I have to find my disassember tool as well because the dumped binary is unreadable in a compiled state. Once it's disassembled things start making sense but any comments or notes in the source code will of been lost.
i'd love to hear what the code does, specifically whart the approach is to maintaining AFR. is there a load/RPM map? (does CEC have a manifold pressure sensor?) |
The CeC only knows of three vacuum states, no vacuum, 4"hg (ported) and 10"hg (adaptive). Anything outside of that or in between it doesn't know of.
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Posted By: FSJunkie
Date Posted: Jun/01/2019 at 3:27am
There is a 4" Hg switch hooked to ported vacuum and a 10" Hg switch hooked to manifold vacuum. With those two switches and a mechanical switch on the throttle, the ECU can determine:
Closed throttle idle. Closed throttle deceleration. Light throttle. Heavy throttle. Full throttle.
Closed throttle and full throttle are open loop, so the ECU just drives the metering rods to a predetermined position regardless of AFR. The only conditions it uses closed loop are light throttle and heavy throttle. It likely maintains 14.7 AFR all the time during a light throttle indication and switches to something richer like 12.5 AFR during a heavy throttle indication. I don't think there is really a map or RPM consideration to it. It just picks an engine load condition and prescribes a fuel mixture, like a power valve in a carburetor.
That's my best guess based on reading the manuals and working on them.
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited
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Posted By: billd
Date Posted: Jun/01/2019 at 9:37am
A friend of mine who hangs out with Eagle folks, he's from a state east of me I believe and an Eagle restoration nut, actually RESTORED an eagle to all its glory with all emissions stuff, all vacuum hoses and lines and it was SOOO COOL to see one restored to that degree and the stuff not ripped out and bypassed.
OK, my 82 SX4 is 4.0 equipped but I DID save most of the stuff I stripped from it- including the "computer" and more. It's sitting around. Rather than toss it i'd like to see it go to someone who can use it. Mine was a Nevada car sold to a CA driver so it came from CA but was originally if I recall a high altitude car from Nevada (not to be confused with Nevada, Iowa) I should have all of the stuff, and I even have a NOS diode board (can't recall the official AMC name) and a NOS set of the vacuum devices that sat in a bracket near the firewall. So anyone wanting to take an Eagle to the same level Matt did with his yellow SX4 (I think it was yellow...?) I have some NOS stuff and the stuff from my own car like the computer shown in the pictures here in this thread.
-------------
http://theamcpages.com" rel="nofollow - http://theamcpages.com
http://antique-engines.com" rel="nofollow - http://antique-engines.com
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Posted By: MIPS
Date Posted: Jun/01/2019 at 11:45am
I could very well poke at one of those as well if people so wished but that too would require modules I don't have.
The stepper motor is peculiar as the CeC limits its operation to something like 16 steps from full rich to full lean even though the motor itself can more accurately step twice as many steps before hitting the end stops. Likewise the motor only takes about 1/4 second to do the full travel, so fine adjustments (within 3-6 steps either direction) while driving are likely happening extremely quickly but it's hard to really get on camera, so here's just full pin travel on a computer with a bad O2 sensor.
https://youtu.be/b_BOvlLOrP0" rel="nofollow - https://youtu.be/b_BOvlLOrP0
Here's another but with a surge condition so you can see the engine constantly trying to lean out and then correct.
https://youtu.be/DsW_zbebotA" rel="nofollow - https://youtu.be/DsW_zbebotA
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Posted By: billd
Date Posted: Jun/01/2019 at 10:19pm
Very interesting research here....... and good info for others to use as reference.
-------------
http://theamcpages.com" rel="nofollow - http://theamcpages.com
http://antique-engines.com" rel="nofollow - http://antique-engines.com
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Posted By: tomj
Date Posted: Jun/02/2019 at 12:56am
thanks FSjunkie for that. with only 16 total? steps there's not a lot of resolution. so it isn't the fully adjustable carb i imagined it might be; i probably shouldn't be surprised but i still disappointed anyway.
so it's probably more like a set of pre-calculated carb settings for a limited number of operating conditions. not hard to imagine you have this complex set of hoses and valves and engine, and a couple of spots are way out of spec, how to pull them into compliance? in 2019 all of this stuff has long been 'generalized' into a computation-based solution; modern EFI doesn't special-case "acelleration" in so far as the hardware is concerned; it's complex calcs, but the same 'simple' injector. the complexity didn't go away, it just moved to a much more manageable technology -- software.
after spending zero effort research feedback carbs (lol), i imagined them as having something like a tapered needle in a jet that had a fairly wide range of adjustment and some sort of closed-loop feedback system. like GM TBI. oh well! hahaha
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: tomj
Date Posted: Jun/02/2019 at 12:57am
this is a really interesting view into the Malaise Era engineering issues. thanks everyone!
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: Greyhounds_AMX
Date Posted: Jun/02/2019 at 7:27am
Unfortunately I don't believe there's going to be anything like a fuel table for you
to find in the code.
As tomj pointed out, up until mid-2000's all oxygen sensors were
"Lambda" sensors, which could only accurately tell if a mixture was
too rich or too lean. There's no scaled output of how rich or how lean, it pretty much outputs
one voltage below stoich and another voltage above stoich. Wide band O2 sensors
didn't see widespread use in production vehicles for another 30 years or so,
and you need a wideband in order to measure the exact A/F ratio if you are
going to use that as a target for performance or mileage or whatever. So the
Lambda sensor can only be used to operate an engine at an A/F ratio of 14.7:1, and if it
measures rich the CeC leans out the carb until the Lambda sensor measures too
lean, then richens until it's too rich, etc, endlessly. That concept continued for decades - my 1995 ZJ worked the same way. The only time it wasn't 14.7:1 was during open loop operation on cold start or during WOT.
It's still
fun hacking on it and learning, but it you want to control A/F ratio via a
table of rpm and load you'll need to add a wideband O2 sensor and use something
like Speeduino maybe. If you want to make a drop in replacement CeC maybe
there's a market for that, but you'd probably have to do it on an
"exchange" basis and de-pot each one in order to re-use the connector
and case. Someone posted that new ones are about $200, which would probably be hard to compete
with as it looks like a lot of work to de-pot the board enough to get at the connector.
------------- 1968 AMX 390 w/T5
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Posted By: MIPS
Date Posted: Jun/02/2019 at 10:35pm
I did not actually see the previous mention for the cost of the connector, however now that I know it's....unpleasant. There isn't really much of a work around then except for as you mentioned harvesting existing ones off other CeC's working or not. I think it might just come down to begging the off-roaders to sell their modules if they've removed their system.
My bad if my thought on the fuel tables was wrong. First time really digging into this so I'm trying to still weed out modern car talk from computers and ECU's because MAN every time I expect this to be something complicated it's just something even simpler. Hmm, perhaps there's a way to just initialize the microcontroller with a different idea of what the "ideal" air fuel ratio is? This may require a little bit of experimenting.
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Posted By: Greyhounds_AMX
Date Posted: Jun/03/2019 at 6:53am
I'm sorry - I was meaning the cost of a replacement CeC was around $200. I haven't been able to find that connector anywhere.
The only way it could control to a different setpoint target than the 14.7:1 would be if it knew the rate of change of the A/F ratio. But the Lambda sensor doesn't provide that unfortunately, so there's no way to do it.
A wideband O2 sensor with electronics package to drive it can be had for about $200 nowadays, which is pretty amazing. But then you'd still need a processor to do the PID loop to drive the carb stepper motor.
------------- 1968 AMX 390 w/T5
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Posted By: tomj
Date Posted: Jun/03/2019 at 10:49pm
A/F ratio isn't measured with a lambda sensor; it's derived, mathematically, from the average over time of lean/rich. that's how GM's TBI does it.
with the engine running the system makes a guess (literally a history-based guess) as to what injector PWM value produces correct mix. of course the lambda sensor does produce that; the code does, indirectly. it's easiest to imagine averaging (integrating) the TIME SPENT LEAN vs the TIME SPENT RICH, and if the rtio or those two values is 0.5, then it's stoich. if its richer than that the PWM on time is reduced; if too lean PWM on time is increased.
this works because the engine is a big block of metal and moves slowly relative to the sensor and software. the code dances around the slow metal.
if you're not a programmer, that's a good intro into how good programmers think up solutions to problems using cheap, crappy sensors.
you could "measure" the temperature of a room by turning the wall thermostat back and forth until the furnace went on, then off, etc, frequently. if its always-on the actual temperature is lower than the thermostat, always off, it's hotter. if it switches back and forth it's "close".
accuracy is relatively limited, and the derived A/FR lags behind in time aa few hundred milliseconds. certainly "good enough" for the 80's.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: Greyhounds_AMX
Date Posted: Jun/04/2019 at 6:57am
In operation, A/F ratio can change almost instantaneously. The time weighting you see used in the control logic is there to add hysteresis around the setpoint so the stepper motor or whatever controls the fuel flow rate doesn't wear out quickly by cycling up and down continuously. Since the Lambda sensor only reports rich or lean and not how rich or how lean, the only way to add hysteresis is based on time.
Engine temperature (or almost any temperature control loop) on the other hand would respond slowly due to the mass of the engine, coolant, etc.
------------- 1968 AMX 390 w/T5
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Posted By: farna
Date Posted: Jun/04/2019 at 11:53am
So in reality you guys are on the same page. Yes, A/F mixture can change rapidly, but with a feedback carb (or cheap TBI/EFI) you don't want changes too often or quick due to parts wear and time to function. So "close enough" is the rule...
Modern port injection can respond faster, but I bet there's still some lag built into the systems.
------------- Frank Swygert
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Posted By: Greyhounds_AMX
Date Posted: Jun/04/2019 at 12:24pm
The point to take home is that with a narrowband Lambda sensor like what the Eagle has we're stuck with closed loop operation that's fixed at approximately 14.7:1 A/F ratio.
------------- 1968 AMX 390 w/T5
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Posted By: tomj
Date Posted: Jun/04/2019 at 11:12pm
i wonder what the goals of CEC were. greyhound is correct, the poor stepper would last a month tgrying to update (and would be too slow).
maybe altitude and temperature (warmup) compensation? that stuff is slow moving.
the carb has the other usual junk doesn't it? accellerator pump and all that?
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: 73Gremlin401
Date Posted: Jun/05/2019 at 12:44am
tomj wrote:
i wonder what the goals of CEC were. greyhound is correct, the poor stepper would last a month tgrying to update (and would be too slow).
maybe altitude and temperature (warmup) compensation? that stuff is slow moving.
the carb has the other usual junk doesn't it? accelerator pump and all that?
|
SFAIK, the stepper-motor doesn't do much other than help to control mixture. the BBD carb itself was augmented differently most every year in response to the prevailing emissions requirements, and the sheer number of BBD variations within a year model was staggering at times. My current driver, a 1980 Concord, has 2 key things hanging off the carb, a throttle 'kicker' that cracks open the throttle at idle when the car is in-gear or with the AC on, and choke is fully off; and a very simple throttle position switch which is looking for an open/closed condition only. I'm guessing that goes to the computer to help it agree with what the 02 sensor is sending it. in 1980 there were still high-altitude/49-state/California carb variations, as well as versions for automatic and manual transmission, as well as several versions exclusively for the Eagles, which were classed differently - so at least 8 versions in that year alone.
------------- 73 Gremlin 401/5-spd. 77 Matador Wagon 360/727. 81 Jeep J10 LWB 360/4-spd 83 Concord DL 4-dr 258/auto
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Posted By: MIPS
Date Posted: Jun/06/2019 at 10:47pm
Here's the official stance on how the stepper motor works in the 2BBD. Keep in mind that stepper motors are typically rated for tens of thousands of hours before failure when they are sealed like this. More than likely poor performance of the stepper motor itself can be blamed on lubrication that has gummed up with age as opposed to bearing wear or an open winding.
My current driver, a 1980 Concord, has 2 key things hanging off the carb, a throttle 'kicker' that cracks open the throttle at idle when the car is in-gear or with the AC on, and choke is fully off; and a very simple throttle position switch which is looking for an open/closed condition only. I'm guessing that goes to the computer to help it agree with what the 02 sensor is sending it |
The first item is the Idle Speed Control Solenoid, or "Sol-Vac". It's a whole circuit that simply bumps the idle up for certain load conditions like you specified, plus can be computer operated when necessary but is not related to O2 sensor operation. The other item is the Wide-Open Throttle switch. Its only purpose is to tell the computer when the throttle plate is within 15 degrees of being completely open. There's more on this below.
maybe altitude and temperature (warmup) compensation? that stuff is slow moving. |
Altitide control on the 82 CeC is controlled by a jumper that is either grounded to indicate you are operating above 4000 feet or tied back and not connected to anything, indicating you are working anywhere below 4000 feet. Remember that this is all-digital so the computer can only receive a YES or NO when it is looking at any sensor (excluding the O2 sensor). The computer does not monitor the status of this signal during operation, so it initializes accordingly when it is powered on.
Likewise the CeC has multiple open-loop modes it will go into depending on what the sensors are indicating when the computer is powered on. This will also affect where the stepper motor sits and remains while in open-loop.
Once all the sensors satisfy their requirements for closed-loop the computer runs a timer to verify everything remains above spec, then enters closed-loop and from then on it is reliant on the O2 sensor and begins full-time stepper motor operation.
I think I mentioned it before in the thread that a working O2 sensor is ESSENTIAL, otherwise you enter closed-loop and the computer will immediately stick you in a max lean or max rich condition which makes the engine run like crap. A very VERY "you must read this" place to read up on all the related sensors above is http://gleebledorf.com/" rel="nofollow - http://gleebledorf.com/ It's more oriented for Jeep configurations but Eagle and similar AMC models use otherwise the same components.
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Posted By: farna
Date Posted: Jun/07/2019 at 7:35am
"...otherwise you enter closed-loop and the computer will immediately stick
you in a max lean or max rich condition which makes the engine run like
crap."
The Nutter Bypass (bypasses the emissions controls) sets the stepper motor in the mid position. Something about when the system is first initialized it starts in the mid position (switch on, engine not running), then adjust rich or lean from there? So you have to have everything connected before removing the CEC system so the carb stays in the mid position. It still won't run as well as a functioning CEC system, but doesn't run like crap because the metering pins are full rich or full lean -- so it runs "better" with the original carb. If you're going to remove the emissions system you need a non-emissions carb, so may as well upgrade to a Weber or Motorcraft 2100. A non-emissions dizzy usually helps as they are curved differently, especially the later models that had some computer timing control .
------------- Frank Swygert
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Posted By: 73Gremlin401
Date Posted: Jun/07/2019 at 11:27am
MIPS wrote:
I think I mentioned it before in the thread that a working O2 sensor is ESSENTIAL, otherwise you enter closed-loop and the computer will immediately stick you in a max lean or max rich condition which makes the engine run like crap.
|
THIS! So very very true. the 02 sensor is everything. Every time I talk with someone about how much they hate how their feedback BBD motor runs, and how they are going to tear everything off, I always ask them if they've replaced the 02 sensor. And invariably the answer is either no, or that they insisted their motor doesn't have one, because it has a carb. And it's just about the cheapest 02 sensor on the market - I think I paid around $5.00 for mine on Rock Auto. yes, it's a pain in the rump to get to, but the instant I changed mine out - I immediately had a better running motor. But trying to convince the 'I'm gonna tear everything off' guys this is like talking to a brick wall.
------------- 73 Gremlin 401/5-spd. 77 Matador Wagon 360/727. 81 Jeep J10 LWB 360/4-spd 83 Concord DL 4-dr 258/auto
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Posted By: tomj
Date Posted: Jun/09/2019 at 10:12pm
73gremlin401 -- ok that makes a lot more sense -- a multi-step rod-in-jet. well within what a stepper can reasonably do.
that's a lot of interim complexity. developing EFI was difficult and slow. it's easy now that a zillion hours have gone into the software.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: MIPS
Date Posted: Jun/09/2019 at 11:05pm
Just a heads up, I went back and re-read the documentation and I am wrong about how many steps the stepper motor can do by a HUGE amount.
AMC Mechanics Manual for 1982, page 1J-61 wrote:
The motor has a Range of 100 steps, but the normal operating area is mid-range (e.g., 40 to 60 steps). |
I said something like 16? That's way off. Take the number above, not the number I said back on page 4.
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Posted By: FSJunkie
Date Posted: Jun/10/2019 at 4:09am
73Gremlin401 wrote:
But trying to convince the 'I'm gonna tear everything off' guys this is like talking to a brick wall.
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No, it's worse. I've talked to brick walls before, and at least when talking to a brick wall all you hear the sound of your own voice echoing back at you and nothing more. Walls don't say nasty things back at you when you tell them something they don't want to hear.
The key to happiness in owning 1970's and 1980's cars is not giving one single flying fack what people think, and caring even less about changing what they think.
That's just owning AMC's in general. You have to not care what Ford, Chevrolet, and Dodge people think and ignore the horrible and totally false things they sometimes say to you.
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited
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Posted By: farna
Date Posted: Jun/10/2019 at 5:28am
The stepper needles in a BBD are tapered, not stepped like Carter carb jet rods. Makes them more adjustable.
------------- Frank Swygert
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Posted By: MIPS
Date Posted: Sep/17/2019 at 11:19pm
I've been pretty busy the entire summer however I was able to get the complete "Super D" ECU system that shipped in Eagles from 1983 onwards. The one pictured below came out of an '87. The last year an Eagle shipped with the AMC name.
The same harness, but this time with 99% of the parts identified.
The ECU itself is still a Ford product but now with a new enclosure, connectors and board layout. This is so new I do not have any diagrams or documentation for it.
While it is a new PCB inside is neither potted or too far different from the previously pictured CeC. This is likely because so much of the harness and so many of the sensors have not really changed since the CeC. There are a lot of similar components. There is also a bit more going on but presumably it is additional control for the purce solenoid and knock sensor. I have however noticed that the part numbers on all the IC's do not cross-reference to their manufacturers. It is likely Ford had the various chip manufacturers print one of Ford's own part numbers on them. That way only ford or AMC could identify components as they had the cross-reference. For the rest of us we were out of luck.
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Posted By: MIPS
Date Posted: Oct/08/2019 at 12:23am
I have managed to secure one of AMC's ET-501 diagnostic kits for the CeC and related wiring. Cost me about $250 shipped.
I've made a writeup on the kit http://www.vcfed.org/forum/entry.php?775-How-did-you-run-an-Emissions-Diagnostic-in-the-80-s" rel="nofollow - here , however I see other much older threads here from people asking for extra info on the tester and notably the manual so (unless Dropbox kills the links) you can download a PDF of the manual that I scanned and assembled https://www.dropbox.com/s/s693xy4v0789ges/AMC%20ET-501%20Instruction%20Manual.pdf?dl=1" rel="nofollow - here and if you are missing the test chips and have the ability to burn new EPROMs you can download their images https://www.dropbox.com/s/jl6155riempathz/AMC%20ET-501%20ROM%20Images.zip?dl=1" rel="nofollow - here .
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Posted By: pacerman
Date Posted: Oct/08/2019 at 10:57am
That is neat. If I can stay away from owning another post-1979 or so AMC I will never need it but thank you for the effort. Joe
------------- Happiness is making something out of nothing.
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Posted By: tomj
Date Posted: Oct/08/2019 at 11:57am
MIPS wrote:
...I have however noticed that the part numbers on all the IC's do not cross-reference to their manufacturers. It is likely Ford had the various chip manufacturers print one of Ford's own part numbers on them. That way only ford or AMC could identify components as they had the cross-reference. For the rest of us we were out of luck. |
the reason for that isn't (primarily) secrecy. it's a side effect of how the semi industry works.
so moto, or national, or ti, or etc, makes a new chip (processor, op amp, whatever) that (Ford) wants to use. Ford's CeC product design life is say 5 years, then then need spares, and development, etc so they will want tthat processor to be available for (guessing) 7 years. National has it's own dev schedule, not Fords.
so National tells Ford if you commit to buying 1,000,000 chips over hte next 7 years, we'll freeze a copy of this design for you. at that point it gets a proprietary part number, and National's existing design is "frozen" over in the proprietary drawings etc.
at least at first, thre Ford part is identical to the National part, and National makes extra money for simply silkscreening a new number on top. but if in say 3 years National wants to "improve" the chip -- which would force Ford to redesign, or more likely, induce possible side effects that could ruin Ford -- National now has to make two chips; the old one with the Ford number, then their new one. that costs more (two production lines) hence the extra charge up front for the proprietary part.
it should be fairly easy to ID the proprietary chip. in 1980 there just weren't many small processors. the two wavy lines (logo) on the big 40 pin cookie i think is National Semiconductor. the hard part will be finding a 1980 Natl Semi catalog! it might be an 8048/8051 second source, or one of their wacky homegrown jobs. you only have to get 90% close. the diffs will be relatively small, like different pins, or a couple of instructions, like GM got out of Motorola for their TBI system; it was a 6811 with a couple of oddball I/O instructions added or changed. those fall out of context in code disassembly.
none of that era's parts had encryption certainly, and lots of them have readable PROM. i assume from the pic of the green board there's no separate PROM/EPROM, so it's a chip masked with code or burned at the factory. assuming you wanna look at the code...
it's functioning is not so complex that you couldn't work out what its doing with a scope, in a running engine... or build a bench-top simulator. for that i'd write code in something dimwittedly deterministic like a 120 MHz "Arduino", my current favorite the Adafruit M4 Grand Central, 54 I/O pins! faster than a 1990's desktop! $30! lol. most of the work there would be translating the 3.3V logic ins and outs to 12V. DIY or buy.
i bet you could guess at most of the inputs and sequences.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: tomj
Date Posted: Oct/08/2019 at 12:04pm
nice investigative work, BTW! ignore the haters, there's a lot of interesting lore in there. and yeah i had a 1975 California V8 Gremlin, with the buckets'o'smog under the hood, and i got it all to work 100% super sweet with all that junk intact. just RTFM and diagnosis and replace all the hoses. the problem with old-fashioned smog stuff is that it's maintenance-intensive; hoses go bad, and no self-diagnostics to display "FILTER CLOG" on a display, it just runs badly!
haters hate vacuum wipers for the same reason. sure there's plenty of reason makers swirtched to electric; but it's not like AMC (or anyone) shipped cars for 50 years with non-working wiper systems. duh.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: MIPS
Date Posted: Oct/10/2019 at 8:58pm
@tomj you are pretty much correct. After spending more time getting used to AMC's part numbering scheme it's becoming apparent that for example a chip that is stamped D9AF-DA and has a suspicious wiring arrangement of a driver can very well be a ULN2074 quad darlington switch, but with a custom silkscreening because a vendor will give you that option once your order quantity goes into the hundreds of thousands or millions of pieces.
Indeed you are correct in that commodity microcontrollers of this era lack virtually any security, mainly due to the unlikely chance at the time a person had both the equipment and the knowledge. 8048's are pretty easy to dump, but the adapters for programmers like my Willem are not cheap, even today. With that in mind, given just how similar the 82 model CeC design is compared to the pictured 87 model MCU, I am going to make a safe assumption that it uses the same microcontroller with an internal mask rom.
Also just in case anyone is wondering if me depotting the first computer damaged it, the tester says it's still fine. Don't know how it concludes that but that's peachy in my books.
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Posted By: tomj
Date Posted: Oct/10/2019 at 9:06pm
that's all pretty freakin amazing. that gear is beautiful. thanks for the great work!
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: pacerman
Date Posted: Oct/10/2019 at 9:42pm
Just an observation but would not the D9 portion of the that part be correct for a 1979 Ford. Was Ford using the same logic software as AMC or more probably, was AMC using Ford hardware?
OK nevermind. I re-read the thread. Of course the were. Joe
------------- Happiness is making something out of nothing.
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Posted By: FSJunkie
Date Posted: Oct/13/2019 at 4:46am
Good to see a 1984 and up "Super D" getting dissected.
All this is leading to the eventual goal of dumping the code off that 8049, altering the code for a custom engine tune, and re-writing the altered code to an external PROM.
That would be really, really cool and allow Eagle owners to get their engines really tuned well. Modern gasoline does not run like 1980's gasoline, so some of the open loop fuel mixtures need adjusting.
I am comforted to see the original code was written in MROM rather than PROM, so it shouldn't deteriorate with age as much as PROM.
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited
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Posted By: tomj
Date Posted: Nov/26/2019 at 4:37pm
currently on abebooks.com is this:
Motor
1983-84 American Motors, Chrysler and Ford Vacuum and Wiring Diagram
Manual/Professional Service Trade Edition (Motor Chrysler/Eagle/Jeep
Ford . Manual Professional Service Trade Edition)
$4.35!!! it's Motors, not AMC, but a trade professional book, not hobbiest. If no one else buys it i might even though i have zero interest in 80's cars.
https://www.abebooks.com/servlet/BookDetailsPL?bi=22667016384&cm_sp=det-_-bsk-_-bdp" rel="nofollow - https://www.abebooks.com/servlet/BookDetailsPL?bi=22667016384&cm_sp=det-_-bsk-_-bdp
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: MIPS
Date Posted: Dec/15/2019 at 8:24pm
So now that I have spent a considerable amount of time over the summer reverse engineering the 82 and 83-87 computers, understanding their theory of open and closed loop operation and constructing my own testing device to compare data the official tool does not show, while I am getting really good at identifying problems it's becoming increasingly clear that the initial goal of a completely new computer to counteract the 80's emissions mandate is probably outside of the scope of my abilities. There are a number of fixed functions that cannot be easily changed without modifying the electronics, thus it no longer becomes a drop-in fix. At the same time there are components the replica MCU's need (such as the harness connector) which are prohibitively expensive (one harness connector for an 82 model year CeC is $230CAD each if ordered in quantities of 10) and not entirely feasable to extract from existing MCU's. At the same time this Eagle has been destroying me for money and I've still been unable to get my hands on an adapter to dump the MCU's code. It's still possible and I really want to do it but I cannot set a timeline anymore. I'm sorry you guys. I'm dropping the ball on this one. We may very well be stuck with the CeC for now unless someone else wants to take a stab at it.
In other news, the manual for the ET-501 tool is now available on the Internet Archive where I can assure you it will be available for far longer than my dropbox.
https://archive.org/details/amcet501instructionmanual" rel="nofollow - https://archive.org/details/amcet501instructionmanual
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Posted By: farna
Date Posted: Dec/16/2019 at 6:18am
Great effort though! Systems like this get obsolete and costly (if not impossible) to repair over time. Once it reaches that point you either bite the bullet and keep it 100% original, or you pull it all and forget originality. If it's a driver I'd pull it... unless emission laws in your area require you to keep it. Most countries drop emissions checking after a car is 25+ years old, but some (like Japan, I think) don't. Even California exempts cars made in 1975 or earlier (repealed a 30 year rolling exemption in 2005). 76 and later are qualified for an "abbreviated" smog check IF they are at least 35 model years old, at least 25 model years old with Historical Vehicle license plates, or classified as a special interest vehicle.
I wouldn't use the "Nutter Bypass" as that leaves the system hobbled, more of a "limp home" state. It works better than a bunged up emission system, but not like it should. Better to bypass everything with a standard carb and distributor. The CEC distributor can be used, but I prefer to get an older model or a new replacement HEI instead since the timing curve is slightly different. It will run better than using the Nutter Bypass, but it still may not be quite as good as a fully working emissions system, especially since the system adjusts the carb on the fly. Just like a regular carb system it will be in perfect tune only under perfect conditions, or the conditions it was tuned for. The CEC system used an O2 sensor and made minor adjustments, which at least in theory should improve gas mileage and power. Not in large increments, 1-2 mpg, 3-5 hp, maybe up to 7-8 hp. Best to get something like a Sniper TBI and replace it all. Any EFI system should be superior to a factory correct/new CEC system, and worth the money and effort if you really intend to drive it for regular transportation. That's why I put a 4.0L with EFI in my 63 Classic.
------------- Frank Swygert
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Posted By: tomj
Date Posted: Dec/16/2019 at 11:30pm
Yeah, MIPS, don't feel bad, you drew out a heck of a lot of information. Knowing when to stop is an advanced skill! It was pretty interesting what you got out of it.
I've often thought of writing closed-loop TBI code or occasionally closed-loop carb. Some equiv. to a 200 cfm 1V carb, 150 hp, with mainly self-tuning for altitude. Something like GM's TBI 2-dimensional RPM vs. mani pressure system, but with a wideband sensor. Knock off all the complicated features. But then I come back to my senses.
Thanks for the work and the pics of nifty, obscure AMC gear!
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: abzman
Date Posted: May/10/2020 at 12:20am
MIPS,
I'm new to the game when it comes to reverse engineering this system, but I've got some electronics skills that I may be able to help out with. I have a 1984 Eagle currently functioning well, but it also came with a bunch of spares. I have a spare second generation computer you've shown here and may be able to dump the program out of it. Were you able to trace enough of the schematic to determine if that's likely the same processor, just relabeled? I know that connector for the earlier computer is expensive, but what's inside it for terminals, might this be a thing someone could design and have 3d printed (just insert the terminals, or make it a pigtail). I'm also somewhat interested in the code in the processor of the original diagnostic computer. I know you posted the roms of the different modules, but the code in the cpu could be helpful in reverse engineering and building a duplicate of that tester. Since I have the later model computer my connector is just an edge connector so for me making a replacement pcb would not be as much effort.
Let me know any way I can help, Evan
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Posted By: MIPS
Date Posted: May/10/2020 at 2:40pm
I'm fairly certain the Microcontroller in the 83 and later MCU's is still just an MCS-48, judging how the supporting circuitry is so similar the the CeC. The MCS-48 uses an external crystal on pins 2 and 3 whereas the MCS-51 which was its successor puts the crystal inputs on pins 18 and 19.
The diagnostic tool itself also uses an MCS-48. It's located behind the front of the tool and is a UV rewritable variant. Again, I do not have the adapter needed to dump it as well. The larger problem is the removable diagnostic ROM piggybacks a large IC that has no markings (on either side) other than it was manufactured by National Semiconductor. My suspicion is that the MCS-48 in the tool is running as a VFD display controller and the unknown chip is actually the main microcontroller which relies on the Diagnostic ROM to operate.
Also don't forget that the harness pinout for your MCU is listed near the back of the ET-501's manual I linked to.
Edited: It's funny actually, someone was talking to me about the Super-D last night. I was sent a partial photograph of the MCU from an 87 year Jeep and while it's clear there was a revision at some point the layout is still quite similar. (and STILL uses an MCS-48, because why reinvent the wheel?) I wonder what that soldered jumper is for?
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Posted By: abzman
Date Posted: Jul/16/2020 at 8:44am
I want to believe that the chip with the socket on top is just a pinout adapter and contains no smarts because I've never seen anything like it and wouldn't know where to start in guessing what it is or figuring out how it's hooked up
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Posted By: FLynes
Date Posted: Jul/31/2020 at 1:19pm
I love reading threads like this, because electronics fascinates me. My father was an electronics engineer at Westinghouse from 1974-1990 and I remember him bringing home these massive HP computers with tiny screens, so he could repair them and run diagnostics. I remember playing Blackjack on one.
If you guys are at a standstill with this project, you might want to reach out to a guy on YouTube, who is an electronics guru, named Paul Carlson. His channel is "Mr. Carlson's Lab". He specializes in old tube electronics, but he also has a newer Pontiac Firebird and has done some modifications to its computer system.
Reading your journey into discovering what makes the CeC tick definitely makes me appreciate the Prestolite ignition system and Carter YF in my CJ-5, although I will admit that I've been very tempted to take my spare module apart to see the guts. I fully understand about talking to brick walls, because so many people, lead by a self-proclaimed ignition expert on the Jeep Forum, are convinced that the Prestolite ignition is crap but, in reality, much like your O2 sensors, it's a matter of Preventative Maintenance. BTW, my ignition and fuel system is still 100% original and I get between 21-23 MPG highway up here in Idaho, 17-19 MPG in the city.
Good luck with your endeavors.
------------- Fred
1976 CJ-5 <font color=LIME GREEN>Lime Green[/COLOR] 258/T-150 3.54:1
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Posted By: MIPS
Date Posted: Oct/28/2020 at 8:29pm
Funny enough, Mr. Carlson lives a few hours west of me down on the coast. I drive past his neck of the woods a few times a year. Legend has it AvE is even closer, but nobody knows for sure. I'm not even sure how you would get in touch with Carlson. Ever since youtube abandoned private messaging years ago I've had no clue how to contact other users.
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Posted By: 5704nMango
Date Posted: Jan/11/2021 at 5:47am
Thanks for all your information on the 196,you have given me the confidence to work on mine. I have a 1962 Rambler American that needs work, engine and body. I have a ton of questions I would like to ask you
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Posted By: ciostko
Date Posted: Feb/07/2021 at 5:50pm
Hello,
I'm in the process of writing my Master Thesis. I will be conducting
tests on parts from the inline 6 cylinder 4.0L Jeep engine. I need to
find out what materials each component is made of and whether they have
any anti-wear coatings.
Parts that interest me:
- engine block (especially cylinders / sleeves)
- crankshaft
- pistons
- piston pins
- piston rings
- main and crank bearings
- camshaft
- camshaft cams
- inlet and outlet valves
I don't need the percentages of the individual alloys. I just need
general information about what is there.
I look forward to hearing from you.
Could you be that kind and help me? Or tell me where can I find those
informations? Best regards
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Posted By: MIPS
Date Posted: Aug/17/2022 at 12:49am
I am still working away at this. It has slipped further down the list of things to do but in the last few months I was asked what could cause the stepper motor driver to blow up as it seems it has happened multiple times to multiple people
As I believe I mentioned a few pages back, the stepper motor on the feedback Carter 2bbd is a 2-phase center tapped device that connects directly to the computer. Inside it is driven by a 16-pin DIP made by National Semiconductor but Ford has put their own custom marking on the chip which you will not find in any parts catalog which makes it very hard to determine what the chip really is and made even harder by the possibility it has not been in production for decades. The best you can do is look at the circuit around the chip to see how the circuit is designed. I went back to my computers and came up with this:
It isn't a dedicated stepper motor driver chip. (which is a little bit of a relief) Two identical chips are used to drive the stepper motor and the solenoids for the Air Management System, the vacuum control of the Sol-Vac and I think the Idle Speed Relay. They are likely high current drivers. Four data lines come directly from the microprocessor, power goes in, you have grounding and you have the signal outputs. In this case the outputs are not "pulled high" (that is the "off" state is equal to ground) but "pulled low" (the "on" state is equal to ground). The stepper motor and everything else when the computer is powered is also getting battery voltage full-time. It just needs the driver to complete the path to ground and the driver is there in the first place because microcontrollers on their own are pretty lousy at doing this and it typically protects the microcontroller in the event of a fault. Why does this matter? The hint was a sticker inside the carrying case for my ET-501 tester warning that when testing vehicles equipped with secondary air, make sure the solenoids are not shorted BEFORE connecting the tool. If the solenoids are shorted (or more likely, the https://en.wikipedia.org/wiki/Flyback_diode" rel="nofollow - flywheel diode has failed in a dead short) when you apply power you force battery voltage with no current limiter into the tester and fry it. The same applies to the drivers in the computer. If the solenoids or stepper shorts directly between battery voltage and the signal pin there is probably no protection mechanism in the chip as the windings should of been doing this for you and it blows up as soon as it tries to pull the line to ground.
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Posted By: MIPS
Date Posted: Aug/20/2023 at 3:36pm
I think I did it. The adapter came in and the ROM seemed to dump and verify back to the microcontroller with the same checksum.
I have NOT however verified if it was a *GOOD* dump. The only way to do that is write the binary back to another chip (like the Intel 8749 which is the same chip, but with a window so you can erase and reprogram the ROM using a UV lamp), plug that back into the CeC and run the MCU test on the ET-501 but right now my programmer has enough umpf to read but fails while trying to write.
So nobody break out the champagne just yet, if reverse engineering an 80's emission system is something to celebrate. In the meantime I quickly fed it through a code disassembler. The code below is from a 1982 model year Eagle with Canadian emissions. It is untested to confirm if it's actually valid.
; ; Disassembled by: ; DASMx object code disassembler ; (c) Copyright 1996-2003 Conquest Consultants ; Version 1.40 (Oct 18 2003) ; ; File: 1982_CDN.BIN ; ; Size: 2048 bytes ; Checksum: 706E ; CRC-32: 29F2FF0A ; ; Date: Sun Aug 20 13:08:45 2023 ; ; CPU: Intel 8048 (MCS-48 family) ; ; ; org 00000H ; sel mb0 jmp L0100 ; L0003: dis i sel mb0 jmp L045A ; sel mb0 sel rb1 mov r2,a mov a,#0F4H mov t,a inc r4 mov a,r4 jnz L0013 mov r4,#0FFH L0013: mov r0,#04BH mov a,@r0 jz L001A dec a mov @r0,a L001A: call L07EE mov r0,#054H mov a,@r0 jz L0022 inc @r0 L0022: mov r0,#02FH mov a,@r0 jz L0028 inc @r0 L0028: jnz L002C anl p1,#0BFH L002C: mov r0,#030H mov a,@r0 jz L0034 inc @r0 jmp L0040 ; L0034: mov @r0,#0F6H call L04EC mov r0,#032H mov a,@r0 mov r0,#02FH mov @r0,a orl p1,#040H L0040: sel rb0 mov a,r3 add a,#09BH jc L0003 sel rb1 clr c jnt1 L004B cpl c L004B: mov r1,#034H mov a,@r1 rlc a mov @r1,a mov r0,#03BH jni L0093 mov a,@r0 jnz L0095 cpl a mov @r0,a mov r0,#052H mov @r0,#0C8H mov r0,#054H mov @r0,#0DAH mov r0,#03DH mov a,@r1 anl a,#00FH jz L006D xrl a,#00FH jnz L0075 cpl a L006D: mov @r1,a xrl a,@r0 jz L0075 mov a,@r1 mov @r0,a jmp L0080 ; L0075: mov r1,#038H mov a,@r0 mov @r1,a mov r1,#04CH xrl a,@r1 jz L0080 mov a,@r0 mov @r1,a L0080: mov r0,#039H inc @r0 mov a,@r0 jnz L008C mov @r0,#0FCH mov a,r4 mov r5,a mov r4,#000H L008C: sel rb0 mov a,r5 jz L0095 dec r5 jmp L0095 ; L0093: mov @r0,#000H L0095: call L0465 djnz r6,L00F8 mov r6,#005H mov r0,#02BH mov a,@r0 jnz L00A6 mov r1,#02EH inc @r1 mov a,@r1 jb0 L00D7 L00A6: sel rb0 mov a,r3 sel rb1 cpl a add a,r3 inc a jz L00D6 jnc L00B3 dec r3 jmp L00B4 ; L00B3: inc r3 L00B4: mov a,r3 anl a,#003H add a,#0BAH jmpp @a ;INFO: indirect jump ; mov r6,#0C4H dec r2 xrl a,@r0 orl p1,#009H anl p1,#0F9H jmp L00D7 ; orl p1,#00AH anl p1,#0FAH jmp L00D7 ; orl p1,#006H anl p1,#0F6H jmp L00D7 ; orl p1,#005H anl p1,#0F5H jmp L00D7 ; L00D6: clr f1 L00D7: djnz r7,L00F8 mov r7,#015H mov r0,#050H mov a,@r0 jz L00E1 inc @r0 L00E1: mov r0,#051H mov a,@r0 jz L00E7 inc @r0 L00E7: sel rb0 mov a,r6 jz L00EC dec r6 L00EC: sel rb1 mov r0,#04EH mov a,@r0 jz L00F6 inc a mov @r0,a jmp L00F8 ; L00F6: call L0500 L00F8: jmp L0442 ; L00FA: call L0550 ret ; mov a,r7 jmp L045A ; L0100: mov r1,#064H L0102: mov r0,#082H L0104: djnz r0,L0104 djnz r1,L0102 L0108: mov r0,#06FH clr a L010B: mov @r0,a djnz r0,L010B call L078B mov r0,#036H mov @r0,#032H ins a,bus jb4 L0119 mov @r0,#019H L0119: mov a,@r0 mov r0,#048H mov @r0,a mov r0,#049H mov @r0,a mov a,#0F4H mov t,a en tcnti strt t mov r3,#064H call L0608 mov r3,#032H call L0608 L012D: sel rb1 mov a,r5 sel rb0 add a,#01BH jnc L0136 jmp L012D ; L0136: mov r0,#031H mov @r0,#0EAH jmp L013C ; L013C: sel mb0 en tcnti call L04A9 call L0712 in a,p2 jb6 L0149 mov a,#089H jmp L014B ; L0149: mov a,#091H L014B: sel rb1 add a,r5 sel rb0 jnc L0156 mov a,r4 anl a,#0FBH mov r4,a jmp L015A ; L0156: mov a,r4 orl a,#004H mov r4,a L015A: call L02E3 mov r0,#036H mov @r0,#032H ins a,bus jb4 L0165 mov @r0,#019H L0165: mov r1,#03CH mov r0,#02AH mov a,@r0 mov r0,#05EH mov @r0,a xrl a,@r1 mov r0,#041H mov @r0,#0FFH jnz L0176 mov @r0,#000H L0176: mov r1,#05EH mov a,@r1 anl a,#007H xrl a,#005H jnz L0186 mov r1,#043H mov a,@r1 jz L0186 mov @r0,#0FFH L0186: mov r0,#05EH mov a,@r0 mov r1,#03CH mov @r1,a mov r0,#037H mov @r0,#000H sel rb1 mov a,r5 sel rb0 add a,#0DAH jc L0199 mov @r0,#0FFH L0199: jmp L060D ; L019B: mov @r1,#0FCH call L0542 L019F: mov r0,#036H mov a,@r0 jmp L0405 ; L01A4: call L03D8 L01A6: call L0542 L01A8: mov r0,#036H mov a,@r0 add a,#021H jmp L0405 ; L01AF: mov a,@r0 jz L01B6 call L01F2 jmp L01A6 ; L01B6: mov @r1,#0FEH jmp L01A6 ; L01BA: mov @r1,#0FFH jmp L0300 ; L01BE: call L03D8 jmp L01A6 ; L01C2: mov @r1,#0FEH jmp L0300 ; L01C6: mov a,@r0 jz L01CD mov @r1,#0FCH jmp L05BB ; L01CD: call L03E8 jmp L05BB ; L01D1: mov a,@r0 jz L01D8 mov @r1,#0FCH jmp L05C8 ; L01D8: call L03E8 jmp L05C8 ; L01DC: mov a,@r0 jz L01E3 mov @r1,#0FDH jmp L01E5 ; L01E3: call L0200 L01E5: jmp L05BB ; L01E7: mov a,@r0 jz L01EE mov @r1,#0FDH jmp L01F0 ; L01EE: call L0200 L01F0: jmp L05C8 ; L01F2: in a,p2 jb0 L01F8 mov @r1,#0FEH ret ; L01F8: mov @r1,#0FDH ret ; mov a,r7 mov a,r7 mov a,r7 jmp L045A ; L0200: jt0 L0205 mov @r1,#0FDH ret ; L0205: mov @r1,#0FEH ret ; L0208: mov a,r4 anl a,#0FEH mov r4,a mov r0,#041H mov a,@r0 jnz L021A jf1 L022F mov r1,#038H mov a,@r1 jz L0231 jmp L02A7 ; L021A: mov a,r4 orl a,#02AH anl a,#0BFH mov r4,a mov r0,#05EH mov a,@r0 jb2 L0229 mov r0,#048H jmp L022B ; L0229: mov r0,#049H L022B: mov a,@r0 mov r3,a clr f1 cpl f1 L022F: jmp L013C ; L0231: mov a,r4 orl a,#008H mov r4,a mov a,r4 anl a,#002H jnz L026A mov a,r5 jnz L022F mov r0,#04BH mov a,@r0 jnz L022F mov r0,#033H mov a,@r0 jz L0249 jmp L0257 ; L0249: mov r0,#05EH mov a,@r0 anl a,#007H xrl a,#005H jnz L0260 mov a,r4 anl a,#004H jnz L0260 L0257: mov a,r3 jz L022F dec a call L0530 mov r3,a jmp L0264 ; L0260: mov a,r3 jz L022F dec r3 L0264: clr f1 cpl f1 call L0428 jmp L013C ; L026A: mov a,r4 anl a,#020H jnz L02A1 mov a,r4 anl a,#040H jnz L028C mov r0,#02CH mov a,r3 mov @r0,a mov r0,#05EH mov a,@r0 anl a,#007H xrl a,#005H jz L0283 call L04AA L0283: mov a,#007H mov r6,a mov a,r4 orl a,#040H mov r4,a jmp L013C ; L028C: mov a,r6 jnz L022F mov a,r4 anl a,#0BDH mov r4,a L0293: mov r0,#02CH mov a,@r0 mov r0,#02DH add a,@r0 inc a clr c rrc a mov r3,a clr f1 cpl f1 jmp L013C ; L02A1: mov a,r4 anl a,#0DDH mov r4,a jmp L013C ; L02A7: mov a,r4 orl a,#002H mov r4,a mov a,r4 anl a,#008H jnz L02C0 mov a,r5 jnz L022F mov r0,#04BH mov a,@r0 jnz L022F mov a,r3 add a,#09CH jc L022F inc r3 jmp L0264 ; L02C0: mov a,r4 anl a,#020H jnz L02DD mov a,r4 anl a,#040H jnz L02D4 mov r0,#02DH mov a,r3 mov @r0,a mov a,r4 orl a,#040H mov r4,a jmp L013C ; L02D4: mov a,r6 jnz L022F mov a,r4 anl a,#0B7H mov r4,a jmp L0293 ; L02DD: mov a,r4 anl a,#0D7H mov r4,a jmp L013C ; L02E3: mov r0,#042H mov a,r4 anl a,#004H xrl a,@r0 mov r1,#043H jz L02F1 mov @r1,#0FFH jmp L02F3 ; L02F1: mov @r1,#000H L02F3: mov a,r4 anl a,#004H mov @r0,a ret ; mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 jmp L045A ; L0300: call L0542 mov r0,#036H mov a,@r0 add a,#02AH jmp L0405 ; L0309: call L03D8 jf0 L0314 L030D: call L0550 L030F: mov r0,#048H mov a,@r0 jmp L0405 ; L0314: call L0547 jmp L0400 ; L0318: mov @r1,#0FEH L031A: call L0550 jmp L01A8 ; L031E: mov a,@r0 jz L0325 call L01F2 jmp L0327 ; L0325: mov @r1,#0FEH L0327: jf0 L0314 jmp L030D ; L032B: mov @r1,#0FFH jmp L031A ; L032F: jf0 L034F mov a,r4 anl a,#004H jnz L0349 mov @r1,#0F9H call L0550 L033A: mov r0,#036H ins a,bus jb6 L0344 mov a,#00FH add a,@r0 jmp L0405 ; L0344: mov a,#019H add a,@r0 jmp L0405 ; L0349: mov @r1,#0FCH call L0547 jmp L0208 ; L034F: mov a,r4 anl a,#004H jnz L035A mov @r1,#0F9H call L0550 jmp L033A ; L035A: mov @r1,#0FCH call L0547 jmp L033A ; L0360: mov a,r4 anl a,#004H jnz L0369 mov @r1,#0FAH jmp L036B ; L0369: mov @r1,#0FCH L036B: call L0550 jmp L033A ; L036F: call L03D8 call L0542 mov r0,#048H mov a,@r0 add a,#021H jmp L0405 ; L037A: mov a,@r0 jz L0381 mov @r1,#0FDH jmp L05BB ; L0381: call L0200 jmp L05BB ; L0385: mov a,@r0 jz L038C mov @r1,#0FDH jmp L05C8 ; L038C: call L0200 jmp L05C8 ; L0390: mov a,@r0 jz L0397 mov @r1,#0FEH jmp L0399 ; L0397: call L05ED L0399: call L0550 jmp L019F ; L039D: mov a,@r0 jz L03A4 mov @r1,#0FEH jmp L0300 ; L03A4: call L05ED jmp L0300 ; L03A8: mov a,@r0 jz L03AF mov @r1,#0FEH jmp L0399 ; L03AF: call L05ED jmp L0399 ; L03B3: mov a,@r0 jz L03BA mov @r1,#0FFH jmp L0300 ; L03BA: mov @r1,#000H jmp L0300 ; L03BE: mov a,r4 anl a,#004H jnz L03C7 mov @r1,#0F9H jmp L0300 ; L03C7: mov @r1,#0FCH jmp L0300 ; L03CB: mov a,r4 anl a,#004H jnz L03D4 mov @r1,#0F9H jmp L0300 ; L03D4: mov @r1,#0FCH jmp L0300 ; L03D8: sel rb1 mov a,r5 sel rb0 add a,#0E9H jc L03E5 in a,p2 jb1 L03E5 mov @r1,#0FEH ret ; L03E5: mov @r1,#0FDH ret ; L03E8: in a,p2 jb3 L03EE mov @r1,#0FDH ret ; L03EE: mov @r1,#0FCH ret ; mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 jmp L045A ; L0400: mov r0,#036H mov a,@r0 jmp L0405 ; L0405: mov r1,a mov r0,#05EH mov a,@r0 anl a,#007H xrl a,#005H jnz L0419 mov a,r4 anl a,#004H jnz L0419 mov a,r1 call L0530 jmp L041A ; L0419: mov a,r1 L041A: add a,#09CH jnc L041F clr a L041F: add a,#064H mov r3,a mov a,r4 orl a,#001H mov r4,a jmp L013C ; L0428: sel rb1 mov a,r5 sel rb0 add a,#0D6H jnc L0439 sel rb1 mov a,r5 sel rb0 add a,#0C1H jnc L043D mov r5,#008H ret ; L0439: mov a,#00CH mov r5,a ret ; L043D: mov r0,#04BH mov @r0,#07DH ret ; L0442: mov a,psw dec a anl a,#007H add a,#0FAH jc L045A add a,#006H rl a add a,#009H mov r1,a mov a,@r1 anl a,#00FH add a,#0F8H jc L045A mov a,r2 en tcnti retr ; L045A: dis tcnti dis i clr a mov psw,a sel mb0 call L04A9 sel rb0 movx a,@r0 jmp L0108 ; L0465: sel rb1 mov r0,#029H mov r1,#028H ins a,bus anl a,#03FH xch a,@r0 xrl a,@r0 jz L0475 mov @r1,#0FDH jmp L04A0 ; L0475: inc @r1 mov a,@r1 jnz L04A0 mov a,@r0 mov r0,#02AH mov @r0,a anl a,#01DH xrl a,#011H jnz L0487 mov r0,#03AH mov @r0,#0CAH L0487: sel rb0 mov a,r4 anl a,#080H jnz L04A0 sel rb1 mov r0,#02AH mov a,@r0 anl a,#007H xrl a,#004H jz L04A2 mov a,@r0 anl a,#007H jz L04A2 mov r0,#033H mov @r0,#010H L04A0: sel rb1 ret ; L04A2: sel rb0 mov a,r4 orl a,#080H mov r4,a sel rb1 ret L04A9: retr ; L04AA: mov r1,#05EH mov a,@r1 jb2 L04B3 mov r1,#048H jmp L04B5 ; L04B3: mov r1,#049H L04B5: mov r0,#02CH mov a,@r0 mov r0,#02DH add a,@r0 clr c rrc a clr c add a,@r1 add a,@r1 jc L04C5 add a,@r1 jmp L04C8 ; L04C5: add a,@r1 clr c cpl c L04C8: rrc a clr c rrc a jnc L04CE inc a L04CE: mov @r1,a L04CF: ret ; L04D0: mov @r1,#0FEH jmp L0300 ; L04D4: mov a,r4 anl a,#004H jnz L04DD mov @r1,#0FAH jmp L0300 ; L04DD: mov @r1,#0FCH jmp L0300 ; L04E1: mov a,@r0 jz L04E8 mov @r1,#0FFH jmp L0399 ; L04E8: mov @r1,#000H jmp L0399 ; L04EC: mov a,r5 add a,#0E3H jc L04CF ins a,bus jb0 L04FA mov r0,#032H mov a,@r0 add a,#0FFH mov @r0,a L04FA: ret ; mov a,r7 mov a,r7 mov a,r7 jmp L045A ; L0500: mov @r0,#0F7H mov r0,#031H mov a,@r0 jz L0508 inc @r0 L0508: mov r0,#03EH mov a,@r0 jz L050E inc @r0 L050E: mov r0,#03FH mov a,@r0 jz L0514 inc @r0 L0514: mov r0,#057H mov a,@r0 jz L051A inc @r0 L051A: mov r0,#033H mov a,@r0 jz L0520 inc @r0 L0520: mov r0,#04FH mov a,@r0 jnz L052E mov @r0,#0F6H mov r0,#03AH mov a,@r0 jz L052D inc @r0 L052D: ret ; L052E: inc @r0 ret ; L0530: mov r0,a mov r1,#036H mov a,@r1 add a,#0F6H cpl a inc a clr c add a,r0 jc L0540 mov a,@r1 add a,#0F6H ret ; L0540: mov a,r0 ret ; L0542: orl p1,#010H anl p1,#0DFH ret ; L0547: call L0559 jz L0542 anl p1,#0EFH anl p1,#0DFH ret ; L0550: call L0559 jz L0542 anl p1,#0EFH orl p1,#020H ret ; L0559: mov r0,#03FH mov a,@r0 jz L056C mov r0,#03EH mov a,@r0 jz L056C sel rb1 mov a,r5 sel rb0 cpl a jz L056C mov a,#0FFH ret ; L056C: mov a,#000H ret ; L056F: mov @r1,#0FEH call L0542 jmp L01A8 ; L0575: mov a,@r0 jz L057C call L01F2 jmp L057E ; L057C: mov @r1,#0FEH L057E: jf0 L0584 call L06F8 jmp L030F ; L0584: call L0700 jmp L0400 ; L0588: mov @r1,#0FFH call L06F8 jmp L01A8 ; L058E: mov a,r4 anl a,#004H jnz L059B mov @r1,#0F9H jf0 L0597 L0597: call L06F8 L0599: jmp L033A ; L059B: mov @r1,#0FCH call L0700 jf0 L0599 jmp L0208 ; L05A3: mov a,r4 anl a,#004H L05A6: jnz L05AC mov @r1,#0FAH jmp L05AE ; L05AC: mov @r1,#0FCH L05AE: call L06F8 jmp L033A ; L05B2: mov a,@r0 jz L05B9 mov @r1,#0FCH jmp L05BB ; L05B9: call L03E8 L05BB: jf0 L05CE jmp L070B ; L05BF: mov a,@r0 jz L05C6 mov @r1,#0FCH jmp L05C8 ; L05C6: call L03E8 L05C8: call L0547 jf0 L05D0 jmp L0208 L05CE: jmp L0300 L05D0: jmp L019F ; L05D2: mov r0,#031H mov @r0,#000H mov r0,#057H mov @r0,#000H mov r0,#050H mov @r0,#000H mov r0,#051H mov @r0,#000H jmp L019B L05E4: jmp L0600 ; L05E6: mov a,@r0 jz L05E4 mov @r1,#0FEH jmp L0300 ; L05ED: in a,p2 jb2 L05F3 mov @r1,#0FFH ret ; L05F3: mov @r1,#0FEH ret ; mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 mov a,r7 jmp L045A ; L0600: call L05ED jmp L0300 ; mov @r1,#0FEH jmp L0300 ; L0608: clr f1 cpl f1 L060A: jf1 L060A ret ; L060D: clr f0 mov r0,#031H mov a,@r0 jz L0614 cpl f0 L0614: mov r0,#05EH mov a,@r0 anl a,#03DH xrl a,#039H jz L0621 mov r1,#03EH mov @r1,#0E2H L0621: mov a,@r0 anl a,#025H xrl a,#025H jz L062C mov r1,#03FH mov @r1,#0C4H L062C: mov r1,#032H mov r0,#05EH mov a,@r0 mov r0,#037H add a,#036H jmpp @a ;INFO: indirect jump ; jf1 L0678 addc a,r2 addc a,r4 addc a,r6 movx a,@r0 ; db 082H ; jmp L0486 ; orl bus,#08AH orld p4,a orld p6,a movx @r0,a jb4 L0694 jnz L0698 anl p2,#09CH anld p6,a mov @r0,a ; db 0A2H ; jmp L05A6 ; mov r0,a mov r2,a mov r4,a mov r6,a mov @r0,#0B2H call L05B6 mov r0,#0BAH mov r4,#0BEH ; db 0C0H, 0C2H ; jmp L06C6 ; dec r0 dec r2 dec r4 dec r6 xrl a,@r0 jb6 L06D4 ; db 0D6H ; xrl a,r0 xrl a,r2 xrl a,r4 xrl a,r6 ; db 0E0H, 0E2H ; jmp L07E6 ; djnz r0,L06EA djnz r4,L06EE mov a,@r0 jb7 L06F4 jmp L05D2 L0678: jmp L01A4 jmp L019B jmp L04D0 jmp L019B jmp L019B jmp L019B jmp L019B jmp L05B2 jmp L01AF jmp L05E6 jmp L01BA jmp L01DC jmp L03BE jmp L07D8 L0694: jmp L04D4 jmp L019B L0698: jmp L01BE jmp L019B jmp L01C2 jmp L019B jmp L019B jmp L019B jmp L019B jmp L01C6 jmp L07CD jmp L039D jmp L01BA jmp L037A jmp L03CB jmp L03B3 jmp L04D4 jmp L019B jmp L0309 jmp L019B jmp L0318 jmp L019B jmp L019B jmp L019B jmp L019B L06C6: jmp L05BF jmp L031E jmp L0390 jmp L032B jmp L01E7 jmp L032F jmp L04E1 L06D4: jmp L0360 jmp L019B jmp L036F jmp L019B jmp L056F jmp L019B jmp L019B jmp L019B jmp L019B jmp L01D1 jmp L0575 L06EA: jmp L03A8 jmp L0588 L06EE: jmp L0385 jmp L058E jmp L07E3 L06F4: jmp L05A3 L06F6: jmp L00FA ; L06F8: mov r0,#03AH mov a,@r0 jz L06F6 call L0542 ret ; L0700: mov r0,#03AH mov a,@r0 jz L0708 call L0542 ret ; L0708: call L0547 ret ; L070B: call L0542 mov r0,#036H mov a,@r0 jmp L0405 ; L0712: mov r0,#050H mov a,@r0 jnz L071E mov r0,#056H mov a,@r0 jnz L071E anl p2,#0EFH L071E: mov r0,#051H mov a,@r0 jnz L0725 anl p2,#0DFH L0725: mov r0,#057H mov a,@r0 jz L072F mov r0,#051H mov @r0,#0F6H ret ; L072F: ins a,bus jb5 L0738 orl p2,#010H mov r0,#050H mov @r0,#0F6H L0738: mov r0,#052H mov a,@r0 jnz L074D orl p2,#010H orl p2,#020H mov r0,#050H mov @r0,#0FCH mov r0,#051H mov @r0,#0E7H mov r0,#055H mov @r0,#0FFH L074D: mov r0,#055H mov a,@r0 jz L0764 mov r1,#05EH mov a,@r1 jb0 L0760 mov r1,#051H mov a,@r1 jnz L0764 mov @r0,#000H jmp L0764 ; L0760: mov r0,#051H mov @r0,#0E7H L0764: mov r0,#05EH mov a,@r0 anl a,#005H xrl a,#005H jnz L0777 mov r0,#054H mov a,@r0 jnz L078A mov r0,#053H mov @r0,#0FFH ret ; L0777: mov r0,#053H mov a,@r0 jz L078A mov @r0,#000H orl p2,#010H orl p2,#020H mov r0,#051H mov @r0,#0E7H mov r0,#056H mov @r0,#098H L078A: ret ; L078B: mov a,#0F9H outl p1,a orl p2,#0FFH orl p1,#020H anl p1,#0EFH sel rb1 mov r5,#0FFH mov r7,#015H mov r6,#005H sel rb0 mov r0,#051H mov @r0,#0CEH mov r0,#050H mov @r0,#06AH mov r0,#057H mov @r0,#0C4H mov r0,#052H mov @r0,#0C8H mov r0,#054H mov @r0,#0DAH mov r0,#02CH mov @r0,#032H inc r0 mov @r0,#032H mov r0,#03EH mov @r0,#0E2H mov r0,#03FH mov @r0,#0C4H mov r0,#039H mov @r0,#0FCH mov r4,#00BH ins a,bus jb1 L07CC mov a,r4 orl a,#080H mov r4,a L07CC: ret ; L07CD: mov a,@r0 jz L07D4 call L01F2 jmp L01A6 ; L07D4: mov @r1,#0FEH jmp L01A6 ; L07D8: mov a,@r0 jz L07DF mov @r1,#0FFH jmp L0300 ; L07DF: mov @r1,#000H jmp L0300 ; L07E3: mov a,@r0 jz L07EA L07E6: mov @r1,#0FFH jmp L0399 ; L07EA: mov @r1,#000H jmp L0399 ; L07EE: mov r0,#052H mov a,@r0 jz L07F4 inc @r0 L07F4: mov r0,#056H mov a,@r0 jz L07FA inc @r0 L07FA: ret ; mov a,r7 mov a,r7 mov a,r7 jmp L045A
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Posted By: 6PakBee
Date Posted: Aug/20/2023 at 8:26pm
I am no computer guru, far from it. But that code dump looks like assembly language. Move, jump, clear, decrement...... Am I close?
------------- Roger Gazur 1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX
All project cars.
Forum Cockroach
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Posted By: MIPS
Date Posted: Aug/20/2023 at 10:48pm
You are correct. Because at that time in history, space was a major limiting factor in computers, the CEC was programmed entirely in assembly. The ROM, or "firmware" as we call it now takes up an entire 2 kilobytes of space. Prior to being written to the ROM the assembly code is compiled to collapse it down further, remove any code commenting that isn't needed in the final product and brings all the components created in the development environment together into one object. Once it's compiled you cannot get any fancy formatting or code comments back, so a utility like DASMx can de-compile the ROM back to how it was (probably) written but we cannot see anything the programmer might of wanted to point out, like state branches, mode switches or how/when it responds to malfunctions. It's up to someone far more educated in assembly (in this case for the MCS-48) to look at the code and see what it's doing.
Between the family reference manual and the programmers reference Intel alone has some 600 pages of documentation. I will admit this is over my head as I am more a hardware person.
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Posted By: farna
Date Posted: Aug/21/2023 at 9:59am
I don't know how much assembly experience Tom Jennings has, but hopefully he will see this and make some comments... even if it's "over my head too"...
------------- Frank Swygert
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Posted By: MIPS
Date Posted: Aug/21/2023 at 11:58am
The goal was that it helps deal with the two most common failures of the CEC:
-Blown output drivers due to wiring problems (I reverse engineered the chip pinout on the previous page, so now we know what to expect when replacing or substituting them.
-Failures associated to "bit rot" as the microcontroller ages. The chip selected by Ford and OEM'd to AMC allows you to select an external ROM and disable the internal ROM by pulling one pin.
Optionally, the Jeep crowd already has experience with the design of the Renix computers. 80's era AMC's are only now starting to gain interest with younger crowds, but there is no substantial amount of technical information to start with for when our computers develop faults. I'm hoping that by going as in-depth as I have I can provide a starting point for anyone else in the years following, rather than it remaining a mystery. That and I'm bored and need to do something to keep myself busy at times.
It does however open the door if someone wishes to completely reverse-engineer the code to substitute computers without alterations to the vehicle harness, since retrieving the firmware was one of if not the hardest part. This was mentioned a few pages back. That especially is far beyond my technical knowledge at this time.
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Posted By: tomj
Date Posted: Sep/08/2023 at 2:16pm
Wow, you've really got a hand on this thing! So that's the entire ROM listing?
I wrote tons of Intel 8080, z80, 8086, 8051 (superset of the 48) and assembly language on a half dozen other micros and minis.
OK post edited. I read the whole thread again.
What's needed to decipher the code is a schematic of the board, so we can know what sensor is connected (eventually) to what pin on the MCU, and a general sense of what that signal does.
You have an amazing amount of information and state about what signals and what order, appears at the connector.
Code like this is I/O intensive -- lots of those instructions are fiddling with I/O pins.
It's been 30 years, but I wrote a lot of assembly language for most of the early (1970s) micros. I can't commit to taking on the rest of the disassembly (IDing, naming, commenting the code) but I'll gladly help.
Here's a readable and complete copy of the programmers manual for the MCS dev system and the chip(s), just FYI. The one on bitsavers is an OCR mess.
https://original.sharpmz.org/download/8048.pdf" rel="nofollow - https://original.sharpmz.org/download/8048.pdf
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: tomj
Date Posted: Sep/08/2023 at 2:29pm
FSJunkie wrote:
...The ECU continuously monitors the knock sensor and the pulses from the ignition coil indicating a spark plug firing for a power stroke on a cylinder....The ECU performs this function for each cylinder individually so each cylinder runs at it's own unique optimum ignition timing. It has no idea which cylinder is number one.
It's genius. |
I missed this 2019 post.
That is genius, and accomplished with so little information. And in a processor to dumb to run a microwave oven (today).
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: tomj
Date Posted: Sep/08/2023 at 3:08pm
MIPS wrote:
The goal was that it helps deal with the two most common failures of the CEC:
-Blown output drivers due to wiring problems (I reverse engineered the chip pinout on the previous page, so now we know what to expect when replacing or substituting them.
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I'd watch for blown commutating diodes, across the solenoids to absorb the inductive dump. Old diodes in this service die relatively often. I'd replace, or augment, with a modern Schottky diode, far more rugged than anything from the past. Cheap insurance. Something like this:
https://www.digikey.com/en/products/detail/vishay-general-semiconductor-diodes-division/SB1H100-E3-54/2146191" rel="nofollow - https://www.digikey.com/en/products/detail/vishay-general-semiconductor-diodes-division/SB1H100-E3-54/2146191
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: tomj
Date Posted: Sep/08/2023 at 7:00pm
That odd-looking 40-pin DIP chip with the socket on the back, appears to be https://en.wikipedia.org/wiki/National_Semiconductor" rel="nofollow - National Semiconductor NS87PC48D, a second-sourced 804x with external 2708 type EPROM socket on top.
https://en.wikipedia.org/wiki/Intel_MCS-48
A photo of one is at the bottom of this Wikipedia page; scroll to just above the very bottom.
------------- 1960 Rambler Super two-door wagon, OHV auto 1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com
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Posted By: MIPS
Date Posted: Sep/11/2023 at 8:58pm
Yeah looking back I did a trace-out of the 1982 computer's circuit board but no good front/back photos. The 1984 computer has front/back photos but no layout diagram. One thing that I could try is pull the IC's and drop them into an "Identifier". they're kind of magic, they probably don't work great and if it's an IC not in its library it won't know what to think of it. On the other hand because it's all probably relabelled parts, as long as they are correct on my assumption of being conventional drivers and op-amps it might let out the last of the secrets. Unfortunately as I'm sure people have noticed I'm a hardware person and have never programmed software in my life. The instruction reference is handy but it will take me quite a while to comment every line.
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Posted By: billd
Date Posted: Sep/11/2023 at 10:50pm
My 82 wiring harness and ECU. Found it interesting what it interfaced with and what it did NOT interface with..... My "coding" such as it was, was limited to VB Script, and programming Juniper and Cisco firewalls, switches and ASAs (routers)
-------------
http://theamcpages.com" rel="nofollow - http://theamcpages.com
http://antique-engines.com" rel="nofollow - http://antique-engines.com
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Posted By: MIPS
Date Posted: Sep/13/2023 at 2:27pm
There's a considerable amount of confusion on the altitude jumper wire that I've seen. The TSM states it's only used (attached to ground) when you regularly drive above 4000 feet. It also states that you will often find this as a crimped eyelet that bolts to the block somewhere behind the distributor. Some models have the wire but it's tied back and not grounded (low altitude mode). In vehicles like mine there is no jumper, but you will find the eyelet with TWO wires crimped to it, but if you compare continuity from ground to the altitude test pin on the diagnostic connector it's open. https://amceaglesden.com/guide/June_1982_TB_1-09-082:_Altitude_Adjustments" rel="nofollow - There's a bulletin stating that for 82 vehicles you have to add an extra pin to the computer connector and run that to a grounded point to enable high-altitude, if your vehicle was not originally built for high-altitude. Alright so this thing has the jumper and it's reading open so whatever, delete it. Yeah, no. I've yet to pull the computer out again (really it sucks to reach) but while one of the wires is a mystery to me and isn't listed in the TSM schematics or the CeC wiring diagram, you will notice the other wire on that eyelet is the ground for the computer. It can ground itself through other components of the system, but it was built to ground everything in the CeC harness through here. Remove that and expect to pull your hair out with computer issues, if the computer works at all.
The 1982 TSM lists the pinout for the connector and where it all goes. I might of posted that near the start of the thread. From the connector pinout you look at the circuit layout but at that point I've yet to link the traces to their respective IC's.
Edited: Page 2. It's on page 2.
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