GTX won't shut off

[moparchris]

Just finishing up a fairly extensive restoration on a 67 Hemi GTX. Pretty much new everything except for outside paint. Car starts and runs fine but when I turn the key it doesn't shut off. Car will keep running for 3-4 minutes and then idle down and die. So every piece of wiring is new. New voltage regulator, new ballast that is correct for a points distributor. Original dual point that has been gone through. Good known alternator. The first 3-4 times I started it and ran it it would shut off properly, but now, no such luck.
I know that this indicates voltage is bleeding through the system but is it possible the voltage regulator could be shorted and keeping the circuit open? That would be so much better than going through $600 of wiring harness to find a short. I had a new ignition switch in inventory and that is easy so I have already swapped the switch with no luck.
Any suggestions will be considered. Thanks in advance.

 

[NoCar2023]

If you disconnected the alternator field wire does it shut down?

 

[moparchris]

Haven't tried that yet. If that works what is it telling me? Is that isolating the problem since that wire comes of of the voltage regulator?

 

[NoCar2023]

I am looking over the schematics right now.
Does it have a tach?

 

[moparchris]

No tach.

 

[NoCar2023]

Haven't tried that yet. If that works what is it telling me? Is that isolating the problem since that wire comes of of the voltage regulator?

Possible regulator? That would eliminate the ignition side of the circuit.

 

[NoCar2023]

Is the Regulator grounded properly? Fresh paint on the firewall?

 

[NoCar2023]

Here is the diagram.

 

[moparchris]

I did clean off the paint behind the regulator and I placed small washers behind it so they would make contact with the firewall. I may just get a new regulator. They're pretty inexpensive and just try it to see. Thanks for all your help.

 

[davek]

Ibought a dash harness from YO and 2 wires were switched. When I connected the starter wound not disengage. Check your wires.

 

[NoCar2023]

Target circuits highlighted (best can do with a mouse)

 

[NoCar2023]

This is the only related circuit I see in the engine harness. Hopefully, it is not in the IP harness.
IGN circuit could also be an issue.
Need to measure the feedback at the coil with a voltmeter and trace it back to the source disconnecting circuits along the way.

 

[w.Hudson]

Most likely suspect is a bad ground. It may have voltage back feed and that is keeping it running.

Could be motor to chassis ground or engine harness ground.

Like someone said earlier, fresh paint could be to blame .

 

[kiwigtx]

Too high an idle and dieseling?

Or is it running normal idle, and not cutting power to the coil?

There may be a crossed wire from the alternator to the ballast resistor, which allows a start & run etc, but doesn't permit shut-off due to voltage output by the still spinning alternator.

 

[kiwigtx]

Ibought a dash harness from YO and 2 wires were switched. When I connected the starter wound not disengage. Check your wires.

Agreed....never trust a part just because it is new from the factory, or fresh out of the packet.

I know this from bitter experience after buying two Holley fuel pumps....the second was because I didn't trust the first. Bitten twice.
Running a Bosch now. One thing is always true...zee Germans make good parts.

 

[khryslerkid]

Car will keep running for 3-4 minutes and then idle down and die.

Sounds like dieseling, running on. Idle set too high? Too rich of fuel mixture?

Place the car in drive and then shut the car off.

Hook up your meter to the 12v side of the coil and when you turn the switch off see if it's still showing voltage.

 

[NoCar2023]

Its dieseling?

 

[moparchris]

No it is not dieseling. It is a run condition. I've built lots of cars. I know the difference. I will go through the engine harness and make sure nothing is crossed. My guess after just having a crappy voltage regulator is probably poor ground issue.

 

[khryslerkid]

Hook up your meter to the 12v side of the coil and when you turn the switch off see if it's still showing voltage.

 

[moparchris]

I will try that. Thank you for the suggestion.