71 Mach 1 wont shut off!

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dhvidston

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1973 Mustang conv 351
Hey all

My 71 Mach 1 starts up and runs great but wont shut off when I turn the key to the off position.

Here is what I tried: Switched starter solenoid with a new one, same problem. Switched again with a known working Autolite solenoid..

same problem.

Removed the ignition starter on top of the steering column and replaced it

with a spare ignition starter that I had on another column ( stored away for 25 years) D1 part#. The spare started the car, no problem.. but still wont shut off.

As a test only...should I be able to start and shut off the car manually by removing the connecting rod from the ignition switch and push the plunger in to "start" and pull the plunger back to "stop" the motor?

I have to pull the coil wire to get it to stop.

Any info is much appreciated!

Doug in Indy

 
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Yes, your proposed test will work. Another test would be to disconnect the electrical wiring connection at the ignition switch, while it is running, to see if that shuts the engine off. Have you checked the voltage to the coil after you get it shut down?

 

dhvidston

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Yes, your proposed test will work. Another test would be to disconnect the electrical wiring connection at the ignition switch, while it is running, to see if that shuts the engine off. Have you checked the voltage to the coil after you get it shut down?
I have not checked the voltage to the coil... would that be to see if it's still drawing?

Not sure if I understand...

 
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1971 Mach 1, Grabber Blue w/Argent stripes. Original 2V 351C Auto, Tilt, rear defog, Black Comfortweave Interior. Under restoration. Original colors, 4V 351C, 4-Speed, Spoilers, Magnums, Ram Air. All Ford parts.
What else have you done to the car lately or is this a first start after restoration. It sounds like the coil continues to get its 12v after the key is turned off. This could be a sticking or shorted contact in the ignition switch in the column, a bad solenoid, or bad wiring. Sounds like you have eliminated the solenoid option so we need to look at the others.

I assume the car continues to run, and not just diesel. Something has you "hotwired" to keep it running.

Let us in on a little of the history and I bet we can find the answer for you real soon. (You never know when Midlife is watching!!)

kcmash

 

dhvidston

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What else have you done to the car lately or is this a first start after restoration. It sounds like the coil continues to get its 12v after the key is turned off. This could be a sticking or shorted contact in the ignition switch in the column, a bad solenoid, or bad wiring. Sounds like you have eliminated the solenoid option so we need to look at the others.

I assume the car continues to run, and not just diesel. Something has you "hotwired" to keep it running.

Let us in on a little of the history and I bet we can find the answer for you real soon. (You never know when Midlife is watching!!)

kcmash

Thanks! Car runs good.. not dieseling or "run-on" but running strong after switch is turned off.

Yes, this is first start off fresh restoration... I replaced the wiring to the coil with correct repop harness for 71 3514v no ac. Old wiring had many splices.

I just manually tested the ignition switch by disconnecting the key rod to the column

and pressed in on the ignition switch plunger.. this started the motor with no problem.

Then, i took a pair of pliers and pulled the ignition plunger back through all it's "clicks" and the motor still would not turn off. this is the second Ign. starter i've tried.

Both are D1 originals,, both had the same result.

Before the restoration, the car would start and shut off just fine

I will try to get a photo of how the coil is wired but we used my brothers restored 72 351 Ram Air conv as a guide when putting back together. His car runs great

 
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There's likely a short or incorrect connection in the repop harness you installed.

Yes, check to see if there is voltage to the coil when engine is shut off and not running, that will give you a starting point. If you do have voltage at the coil, disconnect the wiring harness from the ignition switch and check for voltage at the coil again. If the voltage at the coil goes away you'll know the problem is in the switch. If you still have voltage the problem is probably between the switch and coil.

 
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dhvidston

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There's likely a short or incorrect connection in the repop harness you installed.

Yes, check to see if there is voltage to the coil when engine is shut off and not running, that will give you a starting point. If you do have voltage at the coil, disconnect the wiring harness from the ignition switch and check for voltage at the coil again. If the voltage at the coil goes away you'll know the problem is in the switch. If you still have voltage the problem is probably between the switch and coil.


Brilliant Don! I'll give it a try... will let you know what I find out... Thanks!!

 
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