Car stops running after you let off the key...........

[VegasCharger]

Posting for a friend here about his problem. 1973 Charger when starting runs but as soon as he lets off on the key he claims it stalls. He just added a new 4 pin ECU module when he started having this issue. Attached is a pic of his new ECU install. Sure looks like a 5 pin ECU to me but he claims it's a 4 pin. I did send him a wiring diagram for both 4 pin and 5 pin ECUs to make sure he has it wired correctly. Also I told to make sure that all grounds are intact and he said that they were.

This is definitely NOT my field of expertise so I'm asking in here. I will do my best to help translate between here on DC.com and to my friend who is not a member on here but I suggested he should jump on board.

Thanks, Bryan

[myk]

Ignition switch or ballast resistor?  I'm guessing from a thread I can't quite remember here...

[Pete in NH]

Orange box ECU's are all 4 pin units as far as I know. So, I would suspect a bad ignition switch or more likely a wiring error. If he is using the Mopar conversion wiring harness- Black wire= coil negative, Blue wire to one side of the ballast resistor that goes to the run side of the ignition, also a blue wire. Coil positive to the  opposite side of the ballast resistor and to the start side of the ignition switch usually a brown wire.

[70 sublime]

I would check the resistor first

Just take a test light and see if there is power coming to it when the key is in the run position and going out the other side

Then you would know if the resistor is good or no power getting to it

[ODZKing]

I agree, ballast resistor. That would be the issue on an earlier car with a 2 pin resistor.
The resistor comes into the circuit after the key is released to limit voltage to the coil (I believe it is if I recall correctly). If it is bad, no voltage to coil, hence stall.

[VegasCharger]

Thanks everyone, I'll pass this onto my friend.

[Ghoste]

I've only had one ballast fail in 35 years of Mopar devotion (in spite of the maligned reputation) and that is exactly how it acted.

[VegasCharger]

I've only had one ballast fail in 35 years of Mopar devotion (in spite of the maligned reputation) and that is exactly how it acted.

Thanks Ghoste

I have not heard back from my friend in which he anticipated that he was going to tackle this problem this past weekend.