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CeC technical information?

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MIPS View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MIPS Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post 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?

'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF998/2.35
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MIPS Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MIPS Quote  Post ReplyReply Direct Link To This Post 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.



Edited by MIPS - May/28/2019 at 10:39pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post 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.
'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF998/2.35
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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (1) Thanks(1)   Quote tomj Quote  Post ReplyReply Direct Link To This Post 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.

1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T14
AMC pages: http://www.sr-ix.com/AMC/

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