Engine won't stop?

[Y07Roadrunner]

Today after idling for a little bit I turned off my ignition switch and the engine kept running. I could only get it stopped by pulling the coil wire off. With the key out of the ignition entirely, the amp meter still read in the negative and the parking brake light stayed illuminated - this usually only comes on with the key in the "run" position. The engine starts and runs fine, but the amp gauge reads negative when the engine is running. All wiring connections look good and no other electrical-related issues are observed. Thoughts on this??

 

[PurpleBeeper]

Damn! First guess would be a bad ignition switch. Good move pulling the coil wire!

 

[Darter6]

Just for a test,When running try pulling the alternator field wire and see if it stalls the engine to a stop. You might have a diode that is feeding back.This is just a MAYBE.

 

[Mike67]

Or you could have a shorted bulkhead connector thats back feeding. Pull the switch and with a test light start checking the terminals. You can also check the fuse block with the test light instead of pulling bulkhead apart. Identify the switched circuits, and see if any are hot with the switch off.

 

[PurpleBeeper]

Or you could have a shorted bulkhead connector thats back feeding. Pull the switch and with a test light start checking the terminals. You can also check the fuse block with the test light instead of pulling bulkhead apart. Identify the switched circuits, and see if any are hot with the switch off.

Mike67 has a good idea. "Maybe" start the car, then unplug the ignition switch at the base of the steering wheel. If it the engine stops, then the switch is the problem & very little disassembly required to test it. The short at the bulkhead disconnect (or other dash wiring....mainly in/around the ignition switch wiring IMO) sounds like a good idea too.

 

[Y07Roadrunner]

Mike67 has a good idea. "Maybe" start the car, then unplug the ignition switch at the base of the steering wheel. If it the engine stops, then the switch is the problem & very little disassembly required to test it. The short at the bulkhead disconnect (or other dash wiring....mainly in/around the ignition switch wiring IMO) sounds like a good idea too.

So far we tried a different (and known to be good) ignition switch. Same issue. All alt wires were pulled one at a time and still the issue persists. We have used a test light to show that power is going to the coil even when the key is out of the ignition. Tried a new starter solenoid, and a brand new electronic control module, in case either had a short. Same issue. So from here I think I am stuck tracing wires to find a short.....

 

[Mike67]

Might go ahead and crack open the bulkhead...that really sux!
I never asked and it may sound stupid but has there been any recent electrical work done????

 

[RJRENTON]

Just for a test,When running try pulling the alternator field wire and see if it stalls the engine to a stop. You might have a diode that is feeding back.This is just a MAYBE.

Re possible bad alternator diode...if a diode is shorted the battery will discharge. If a diode is open, the alternator's capacity will be reduced by half. Early Mopar alternators are three phase full wave units...loss of a diode in any phase will result in low CURRENT output under load.
Bob Renton

 

[PurpleBeeper]

Yeah, I think you need to trace wires. Just start at the coil and keep going back upstream until you don't have any power with the key off. Coil to ballast to bulkead along both the blue and the brown wire, bulkhead, wiring to ignition switch.....I think that's all. I'm pretty sure you're draining the battery while the engine is off.

Now this is out of left field....what happens when your amp meter goes whacky? Doesn't most/all of the power run through it????? Total guess

 

[Y07Roadrunner]

We FINALLY tracked down the issue to a bad connection in/at the electrical plug about 12 inches back from the alternator. Two wires had a crappy connection and overheated. This melted several wires together. Fixed these 2 wires and all is well again. Since the wiring harness runs along the inside of the valve cover and under the base of the air cleaner you can't even tell the harness has been apart. Thanks to everyone who weighed in on this!!!!!