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Eagle 258 Carter BBD hesitation. |
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Heavy 488 
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Joined: Apr/27/2019 Location: In the Status: Offline Points: 3557 |
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 Posted: Oct/22/2019 at 9:43pm |
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Can't hurt. Strange though it isn't initializing when it's powered up. It needs that start position.
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zeebo76
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Joined: Oct/09/2019 Location: Washougal, WA Status: Offline Points: 158 |
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Posted: Oct/22/2019 at 9:49pm |
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Yeah, I was thinking the same. The way I was able to check its initialization phase by myself is because I just stuck the connector harness onto the new stepper motor and leaned it up against the windshield. Flipped the key on... Nothing. Off, on... Nothing. On off on? Still nothing. On off on off on off on? Nope. Cranked the engine for about a half second and... Yep, it's moving.
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tomj
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Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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Posted: Oct/22/2019 at 10:39pm |
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i dont know how the4 ECU controls the stepper, but i know steppers very well, written tons of code for them in other contexts. and in closed-loop systems. steppers have two coils minimum, and a complicated pair of timed signals/currents that sequencer the coils to "walk" the rotor in one direction or another. each step is a fixed angular rotation, 100 to 300 steps per revolution. they dont' power on like a regular motor. one step at a time, like 0.9 or 1.8 or 3.6 degrees per step. applying 12V to one or both coils will only make it hot. maybe, it iwll make it momentarily jerk. steppers have no idea where they are -- there's no absolute position sensor. absolute position is a PITA so a trick is used instead, in many situations, and i'm sure, in the BBD: * on it's own, removed from the carb, the stepper can go round and round without limit. * installed in the carb, there are only so many steps CW, and CCW, before whateveritis stops rotation. a needle into a seat, all the way in or all the way out. metal strikes metal, and the stepper motor stalls. * on power-on, the ECU has no idea where the needle/stepper is. but it needs to know where it is to do it's function. so on power-on this trick is used: * assume that it takes 100 steps to go from all in, to all out. whatever that number really is... * at power on, run the stepper motor INWARD 101 steps. now the ECU knows that the needle is all the way in. * now the ECU knows where the needle is -- all the way in. from there, until you turn the car off, it counts steps out, and in, to know position. so at power-on, if the needle is already at the position it wants to start in -- all the way in? all the way out? then it wont make any noise at all/wont step. more precisely, it will run the 101 steps (or whatever it is) but the motor won't actually move if it's already out/in. if you wanna test that, turn the car on, assume the ECU./stepper does its thing, turn off the car, manually rotate the stepper to the far OTHER position, whatever it is, and turn the key on again. THEN it should take 100 (etc) steps, which ought to be noticable. closed-loop stuff is notoriously difficult to debug and diagnose. i always wanted to write a closed-loop, feedback-carburetor ECU program. if only there were a one-barrel feedback carb... |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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farna
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Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19689 |
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Posted: Oct/23/2019 at 6:07am |
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Not only is there a one-barrel feedback carb, but it's one of your favorites -- Carter YF (actually YFA)!! It was used on some mid 80s Fords. I just checked on availability... every "YFA" I saw sold as a replacement was actually a YF -- no feedback function. Apparently most take the electronic controls off and go to an older version. Works better than malfunctioning feedback system... and we all know the system can be a pain to go through and sometimes find the right parts for.
Edited by farna - Oct/23/2019 at 6:12am |
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Frank Swygert
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tomj
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Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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Posted: Oct/23/2019 at 11:03pm |
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woah! i had no idea! haha thanks for that! lol, the last thing i need is inducement to mess with the '68! i'll poke around for applications. and look for what the strategies were for them. i'm fine making carbs work and maintaining them. altitude compensation would be a huge boon for me. thanks frank! |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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FSJunkie
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Posted: Oct/31/2019 at 12:56am |
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If we are still on the subject of off-idle bogs or hesitation, don't forget to look at the EGR. I've had several engines with off-idle problems that were caused by aftermarket EGR valves with the wrong flow characteristics. The aftermarket valves are designed to work in a wide range of applications and use replaceable orifice washers to calibrate them to a particular application. Finding the right valve and washer involves faith and guess work even when you have the OEM valve number. Getting the wrong one dumps too much exhaust into the engine too quickly and causes a nasty bog.
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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tomj
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Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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Posted: Oct/31/2019 at 9:09pm |
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i'll concur on the EGR thing, it's critical to have the right pintle to get the flow right. it's fairly open-loop i think. the one time i messed with this, on a 1975 California V8 (304) Levi's Gremin, i finally bought an NOS CA-only EGR valve, was $100! (15 years ago)and man, it ran great, with EGR and the rest of thew bucket'o'hoses smog stuff working right. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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dodgerammit
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Joined: Apr/26/2019 Location: TN Status: Offline Points: 151 |
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Posted: Dec/12/2019 at 7:32pm |
Okay, so does the center pin actually rotate, thus causing the metering pins to move in/out
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84 Grand Wagoneer Garnet Red (mine)360/727/229 44/20
84 AMC Eagle Wagon (Wife's) Deep blue 258/mushbox/129 30/15 |
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tomj wrote: