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I have a 1976 Plymouth Fury and it has a 5 pin ignition control module. The only replacements I have found are the 4 pin and the 5 pin for trucks that have a reversed pin-out. If I’m not mistaken the 5th pin is a redundant ballast resistor bridge and the 4 pin ICU will work if only through a minor wire alteration instead of a whole rewire for the truck 5 pin. Am I correct in my understanding from the limited access of the few remaining wire diagrams and from talking with the even fewer mopar old hats that remain? If anyone has experience or an idea to work off please let me know. The mid-70’s to mid-80’s MOPARs are a construct of terribly implemented great ideas that never turned out right, and i’m lost. :silly:
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see if this helps.
I’m on my 5th Napa ignition control unit and none gave any spark at all. The original ICM still works perfect until it warms up and then loses all spark. Is it even possible to get that many bad units when everything tests good without any wire issues, and the original unit still simi-functioning? I have checked and rechecked everything but can’t get a new unit to work at all.
I have finally found the issue. Thanks guys, but after talking a technician into some diagnostic time for yard work, we were still at a loss after 2hr. We both made the mistake of not ruling out everything and then accidentally dropped a ICM on the block when it rattled free to have it fire right away. Turns out not 1 of the 7 had a case ground except for the heatsink. Thanks for the help
The 4-pin unit just moved the resistor inside the unit.
The resistor is in series with a Zener Diode inside the unit to create the ECU internal voltage reference.
You should be able to just install the 4-pin ECU with no other changes.
Note that these ECU units are sensitive to ground loop problems.
The magnetic pickup signal may not be detected if the ECU is at a different ground reference level then the engine block/distributor.
The module grounds through the body, so you should have a engine ground to ECU/firewall cable.
One indication of bad ground(s) and battery cables is if will not start when cranking the starter (high load), but then tries to fire when the starter is released (low load in battery cables.)
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