Key off but engine keeps running?

[wengr]

After a drive today, I parked and tried to shut the car off. the key turned and came out of the ignition switch as usual, but the engine kept running. radio stayed on as well. I had to open the hood and pull the wire out of the coil in order to stop the engine. Should I expect some sort of problem between the mechanical part and the electrical part of the ignition switch? If so can it be dismantled and repaired? thanks greg

[So Cal Mark]

I would expect a shorted switch, but I'd also look at the harness connector from the switch. They can melt, and possibly short two wires together

[wengr]

Ok, I have inspected the harness connector, and this one is not melted and shows no sign of overheating past or present. Also there is a small two wire connector, and that looks fine as well. I was surprised to find that while the car is running, I can disconnect both connectors coming of the ignition switch, and it keeps running. I have no reason to believe the wiring has been modified in the past. In order to shut the engine down, does the ignition switch open a circuit? Or does it short two wires? I would have thought it opens a circuit, but if so I would think the engine would stop when I disconnect the switch?

[So Cal Mark]

turning off the ignition should remove power from the coil,thus causing the spark to cease. It's sounds like the charging circuit is powering the ignition

[mdrburchette]

Have you upgraded the ignition system or changed anything on your car? I'm asking because I had the same thing happen with my 72 after I installed the MSD box and coil. Evidently, there was still a small amount of current running through the system that it kept the car running even after it was shut off. I had to install a diode in the excitor wire. Diodes are used to allow voltage to flow only one way.

[wengr]

Thanks for the replies. I have not modified the ignition system in any way. coil, module, ignition switch, and wiring harness appear stock and unmolested. I assumed it was the switch until I unplugged it from the harness, and it still does'nt stop. Now I'm wondering if there is a relay for the ignition circuit that could be sticking on? I understand that Brad Artigue has electrical diagrams up but for some reason I cannot access the site.

[rlux4]

Brad's diagrams are a must have. Try this link:
http://www.artigue.com/?page_id=30
Good luck.
Ron

[pope]

Sounds like the Timing is off, as in from the time that you pull the key to the time it shuts off. LOL

[mbouse]

maybe you think you already answered this, but did you change the voltage regulator and/or the alternator recently?

[wengr]

Thanks Ron for the link, that one works for me. Mike, I have not done anything with the alt. or regulator. does anyone know, If the car is running, and you unplug the ignition switch - should the car stop?

[mbouse]

YES. the pink wire that feeds the coil comes from the ignition switch.

if you are seriously attempting that as a test, either don't look at the plug while you pull it out, or wear some safety glasses...

[wengr]

Mike, I have been doing it for the past two days. Must have done it 20 times or so. Disconnecting\reconnecting both the large connector that sometimes melts, and the small two wire conector while the car is running. There is no sparking, no arcing, actually no effect whatsoever. If there is no relay in the ignition circuit, then I guess I don't understand how it works and it actually needs a new switch.

[mdrburchette]

So you pull the wires at the switch and it keeps running? It looks like you've eliminated the ignition switch to me. Wonder what would happen if you try pulling the exciter wire at the alternator to see if that kills it. Btw, where does the exciter wire go on a newer model? Maybe disconnecting the other end would be safer.

[danaspider]

Oh god, I hoped I would never see this in our little cars, but had the problem in a 86 Porsche 911, possible causes:

_ master relay bad, that is the big multi relay for the ECU. same in the FI cars as 911
_ as Mark said the rectifier in the charging circuit, could be half waving, (some of the diodes bad) can cause this.

- Now the really bizarre one, but the one that got me going again ......


wait for it.....

Look at all of your bulbs in the car. A shorted bulb can do this!!! I am an engineer and still don't have a grip on it, but that fixed the Porsche!!

[wengr]

Thanks everyone for the helpful replies. Maybe I'm mistaken, but I had discounted the alternator because the dash lights stay on after I purposely stall the car.
So to recap:
I turn the key to the off position and remove it
Nothing changes - car keeps running, all circuits that were powered stay powered, radio,etc.
I apply the brake and let the cltch out in first gear to stall the car
engine stops, but the dash warning lights stay on, just like when the key is in the run position with the engine off.

So my thinking is how can the charging circuit responsible for the dash warning lights when the engine is not running? But completely disconnecting the ignition switch from the harness does not stop the engine or turn the warning lights off. I did'nt know we had a master relay for the ecu. I'll check into it, and the bulbs. greg