Engine runs with key off

[Ron.G]

Here's a good one.
I turned off the ignition switch and the car would not shut off. I went to pull the coil wire and noticed my parking lights were on so I turned them off and the car shut off.
The lights seem to be back feeding the ignition.
when I turn the key off and the car is still running, the tack behaves oddly and the alternator light comes on.
Otherwise the car runs fine and all the lights work like they should.
No alarm system or hack wiring.

What would cause this? I have never had a electrical issue with the car.

1980 3.0 SC

[leadrsa729]

Sorry I'm no help here because this same exact scenario is happening to me in a 72' 911T. Stock wiring, no real big changes except for routing one smaller battery from the smugglers box rather than two big batteries from the battery boxes. Interested to see what others might have to say.

[rsscotty]

Try putting a diode in your alternator light circuit. MSD ignition has a technical article about this feedback issue from the alternator. They used to provide a diode in their MSD 6AL kits they sold.

[AVDCAV]

Diode will fix this , I think jw put a post up ages ago
That's what I read as well . Did the diode in minutes and fixed

First time I was like. Whatttttt. I was at a restaurant with a very nice suit on
With zero desire to play with my car.

Remember diodes only work in one direction.

[john walker's workshop]

i remember years ago, a car that kept running until you took your foot off the brake pedal. seems there was a single filament bulb in a dual filament socket that bridged the two terminals. can't remember what year it was.

[wayner]

I think it is a bad connection on your ignition circuit so it is taking an alternate path through your lights somewhere.

[Ron.G]

I did have an issue with the right rear tail light recently. I will go there first and see if the problem stems from there.
The bulb socket is a little to big for the bulb so I put in a very small piece of sheet metal between the bulb and the socket to get a good ground. I am pretty sure that has nothing to do with it but there may be something else going on back there. Maybe the bulb is not in quit right.

I'll pull the bulb and see if this issue goes away.

Thanks for all your suggestions, I'll get back to you shortly.

[Trog]

My PMO ITB Project

[Falnaim]

Hi all,

My car 1987 930 turbo will not stop running even after i remove the key?

I stall it in first gear to shut 's off

Regards,

Falnaim

[mhicks85]

Hi Ron, I agree with John. Make sure everything is correct with the electrical system before make unnecessary additions. Incorrect bulbs or wiring mods (alarms) can cause unexplainable problems. Did the car work prior to the bulb modification?

[Ron.G]

We have a winner!
John Walker and his wisdom comes through once again.
I would have never thought that it would be a tail lamp that would cause this.

I put one of the single filament bulbs in were the stop (double filament) belongs by mistake when I took them all out to clean the sockets.

The car shuts off as it should now.

Thanks to everyone for you help.
Ron.

[john walker's workshop]

chicken dinner!

[Ron.G]

This forum is lucky to have you John.

[Falnaim]

I always respect your answers long time ago....Thumbs up

chicken dinner!

[RSTarga]

really !!! experience trumps logic. I thought it was your ignition switch.

[Ron.G]

I am glad it wasn't. not ready to tackle an ignition switch.

[DBDP]

Wow, without the internet, this amazing forum and the answer by john think of all the grey hairs and sleepless nights that could have caused. This ones getting stored in the mental vault.

[fanaudical]

I just found a similar electrical issue stemming from a bad relay for the heater blower fan in the engine compartment on my '75. (Relay had an internal fault that kept the power on the ignition when the key switched off.)

Looking at the schematics, it seems that Porsche "daisy-chained" a lot of power and ground wiring. Single-component failures then create havoc with various circuits.