69GT
Well-Known Member
I could use some help solving an electrical problem I have. I have a 70 340 Dart that has what appears to be a reproduction engine harness with the built in electronic ignition wiring. The electronic ignition control unit that came on the car is pretty ratty looking (it is an original factory installed type ecu from the 70s, not a MP part) so I bought a Mopar Performance chrome unit for it. I hooked it up only to find the car would not start as there was no spark. After trying several other control units from my other cars that also didnt work, I noticed that the original ratty one had five pins in it compared to only four pins in the others I tried. If I put the old unit on the car it will start right up. After looking at the engine harness I discovered there is a double plug not plugged into anything tucked down behind the washer bottle near the ballast resistor. The plug has a blue wire and a green wire with red tracer. I believe it is a double plug for a four post ballast resistor. The car only has a two post ballast on it. I have read that a four post ballast is required with a five pin ecu for the car to run but mine does run with only the two post ballast. I know when installing a Mopar Performance electronic distributor kit it says to snip that green/red wire off of the ecu plug as it is not used so I was thinking the problem must stem from that extra pin on the ecu. However, being that it isnt connected to the ballast on the opposite end I would think it would be just the same as if it were snipped. Anyway, I have racked my brain trying to figure out how to get around this in order to be able to use my chrome ecu but I just dont know what to do short of replacing the engine harness with an original and wiring the electronic ignition the same way as if I was installing an MP electronic ignition kit. If anyone else has encountered this type of problem or anyone knows what I should do to fix this I would appreciate your help very much.
