72 Starter stayed engaged

[Gary42]

I had a hair-raising experience this week. When I started my '72, I noticed an odd sound coming from under the hood. I quickly realized that it was the starter and that it had failed to disengage even though I had turned the key back on the ignition. I tried moving the key back and forth, but I couldn't release the strater OR kill the engine! I didn't know what to do. Fortunaterly, the engine stalled within about 15 or 20 seconds of this. The starter is probably cooked now. Worst-case scenario is broken teeth on the flywheel. Best case: just a bad starter. Here's the odd thing: the ignition key now turns power on and off in a completely normal manner. It's not stuck closed. Why couldn't I stop the engine when the starter was stuck on? Anyone ever have this happen? Also, how hard is it to change a starter on a 72? Looks easy enough from my cursory inspection.

 

[Tom B Hargrove]

I did. When the solenoid engages, it keeps getting power until it disengages, regardless of the ignition key's position. You have to unhook the power to it to make it stop. Mine did it when I put the engine back together and used a different starter. It was binding on the flex plate and holding the starter engaged. You might need to shim it get it sitting right. Check your starter bolts. There might be other things that will make it stick, but that was my problem. Hope this helps, Tom

 

[JohnZ]

You couldn't shut it off because as long as the solenoid is engaged, it's supplying 12 volts to the coil from the small "R" terminal on the solenoid to the coil (+) terminal through the 20-ga. yellow wire; that circuit supplies a full 12 volts to the coil during cranking instead of the resistance wire-reduced voltage from the ignition switch. When the engine starts and you release the key, the bypass circuit drops out and the coil gets its power through the resistance wire from the ignition switch.

 

[Gary42]

I did. When the solenoid engages, it keeps getting power until it disengages, regardless of the ignition key's position.

Thanks for the info, Tom! I was really concerned that I was looking at not only a starter problem, but (more dreadfully) an electrical problem as well. A starter change-out I can handle!

Gary

 

[GaryS]

Starter replacement on a 72 is fairly easy. I had to loosen the exhaust downpipe to get mine off. However the rest is quite easy. Make a note of the positions of the wires and, of course, disconnect your battery. Lots of volts down there. I agree that you have a bad solenoid. My local starter/alternator shop rebuilt my buddies 73 starter a month ago for $65 and only took about an hour. We actually stood there and watched him put in all of the components. Please ensure you use good jack stands when you have the car up.
Gary
72 LT1

 

[mrvette]

This scenario is the reason why I recommend putting ALL the small wires on the inside terminal, that way the 12 volts to the solenoid from the key switch ALSO feeds the ignition hot, so IF that solenoid hangs up, turning off the key switch will kill the engine....


A buddy of mine some years ago, on his SCCA race car, installed a fresh momentary paddle switch for starter, open headers, of course....

so they go out on the track, headers blaring, hearing protection/helmet in place, and of course the switch hung up internally NOT releasing the starter, so about ONE lap allmost completed and the thing tossed sparks and all crap all OVER The place.....

starter was in orbit as engine was cruising about 6000 rpms'....one can only imagine...

GENE

 

[Stallion]

Where is the starter solenoid placed in our C3s?

 

[Gary42]

Starter replacement on a 72 is fairly easy. I had to loosen the exhaust downpipe to get mine off. However the rest is quite easy. Make a note of the positions of the wires and, of course, disconnect your battery. Lots of volts down there. I agree that you have a bad solenoid. My local starter/alternator shop rebuilt my buddies 73 starter a month ago for $65 and only took about an hour. We actually stood there and watched him put in all of the components. Please ensure you use good jack stands when you have the car up.

I began the process of removing the starter this afternoon. I'm a slim guy, so I fooled myself into thinking that I could do the job w/o jacking up the car. Silly me. The starter's very accessible, but removing all of the small nuts holding the power wires on in such tight quarters is not really feasible. Had to borrow a jack and jack stands from a buddy. Updates will follow when I get back to work...

 

[Gary42]

Update on the tale of starer woes: I got the old one out, bought a rebuilt that matched the old one exactly. After much grunting and straining, I got the new one in without having to remove the left exhaust . This is where I really wanted a lift or a seperate pair of hands. Trying to lift a 20 pound starter with one hand while trying to thread reluctant bolts with another all the while on your back is a real trick. Anyway, I was thrilled when I hit the key and she fired right up. I started and stopped the car several times after that and things were fine. Tonight, I went to start the car and I heard a low whine after the engine turned over. It got louder and higher pitched. Again, I could not turn the engine off by moving the key...just like the first time this happened. I had to pull the quick disconnect on the battery to kill the engine.

Now, when I reconnect the battery...even with the key out...the starter spins up without engaging the flywheel. I can't get it to stop doing this. The elctrical connections are all as they should be. Anyone ever have this happen? You guys were really helpful before, I'm hoping someone can shed some light again. It's got to be an electrical issue, right? Maybe one of the wires is frayed under all that electrical tape.


Gary :cry

 

[hazbin]

replace the ignition switch