SCARY Ignition Problems

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Jul 22, 2010 | 09:46 PM

mygreen73

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From: Nashville

SCARY Ignition Problems

I have a '73 dentside that has a mind of it's own. The latest problem is intermittent. Sometimes when you start the truck, you hear that the starter motor and flywheel continue spinning (won't disengage when key released to the "Run" position.) Additionally, if you turn the key to "Off", the engine and starter keep running. Pulling the key out - still runs...You have to go pull the battery cable to get the truck to turn off. If you touch the battery cable back to the battery post - the truck starts without a key.

I thought it might have been an ignition switch issue, so replaced it and it seemed fine for a few days until today. Same problem as before.

The starter solenoid is a new Motorcraft. The solenoid positive post only has the battery cable, horn relay wire, and main harness wire connected like it should. Other electrical things replaced in the past month, Motorcraft voltage regulator, battery cables, horn relay.

I've checked the entire harness for problems, pulled the dash and checked all connections etc. I can't think of anything that would cause this. Any ideas?

Jul 22, 2010 | 09:58 PM

brown79

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did you replace the solenoid recently? i put a new one on and the first time i hit the key it did that. lower quality third world produced electrical parts can be junk from new

Jul 22, 2010 | 10:00 PM

mygreen73

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From: Nashville

Yep a few weeks ago. It had a bad one in there (wouldn't start and was an off brand replacement) so I replaced with a better Motorcraft. Think I should try another new one?

Jul 22, 2010 | 10:01 PM

supawah

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mine did that before i replaced the distributor pickup coil, i think it was engaging thesolenoid through the ign terminal?

Jul 22, 2010 | 10:20 PM

mikeo0o0o0

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From: Stanley, VA

Quote:

Originally Posted by supawah

mine did that before i replaced the distributor pickup coil, i think it was engaging thesolenoid through the ign terminal?

A '73 won't have a pickup coil unless it's been converted to electronic ignition.
It sounds like the solenoid is sticking. To check it, if it wants to keep cranking over without the key in the start position. When it's cranking disconect the small wire marked "S" on the solenoid. If it stops cranking you have a wiring problem. If it keeps turning over the solenoid is sticking.

Jul 22, 2010 | 11:04 PM

mygreen73

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From: Nashville

Thanks. Good advice on the solenoid check. I'll do this tomorrow when it acts up again. I'm hoping it's not the wiring. It's been a real bear to undo the PO's handiwork.