91 TSI - engine will not turn off! Help!

[Wizeman76]

Ok, I turn the car on, it runs and drives great. I go to turn it off, take out the key, and the engine is still running. All the interior electronics - radio, fans, wipers stop working, but the cluster lights and tach are all still on with the engine still running. You can rev it up, drive it all you like but it wont turn off. Even if you stall it, the cluster lights are stll on, killing the battery.

I have no turbo timer installed, I've tried wiggling the key iginition switch - even unplugging it with no effect. The only way I've managed to turn it off is either by unplugging the ecu, unplugging the small metal box next to the ecu, pulling the MPI fuse in the engine bay. I tried pulling the IGN fuse but it had no effect.

I've tried 3 different working ecu's, all do the same thing. I even changed that little metal box next to the ecu with one from a working car. The engine will contiue to run untill the fuel runs out. I really can't figure it out. Can anyone help me? I'm considering wiring a kill switch using that MPI fuse but I'd rather have the car working correctly.

 

[luv2rallye]

Check for stuck-on MPI relay.

 

[Wizeman76]

Thanks for the reply. After I started the thread, I took note of the red and black wire leading from the MPI fuse. It ended up leading to that small metal box next to the ECU. I'm assuming thats the MPI relay - because I wired up a switch to that wire, and now the car switches off great. Looks like a stuck on MPI relay.

The thing is, I changed out the relay with a working one and I had the same problem. After I wired up the switch, the car will shut off great even without flipping the switch. Which has got me confused. The switch is a three pin toggle with a ground, live and an illumination. I wired the MPI wire to the ground and illumination. So with the switch wired up, the car turns off - without flipping the switch. So I'm happy.

The problem is still there but also its not. Confused? Me too! I'll try not to worry about it.

 

[luv2rallye]

I'd have to see a wiring diagram of how you wired the switch to understand why it works (and if you're even doing it correctly). But your original problem sounds like you may have had 2 MPI relay harness wires shorted together since you said replacing the relay had no effect. If the problem was there without the relay even in place, these wires would be the black-red on relay pin 10 shorted to either of the reds on pins 4 or 5, OR either of the reds on pins 4 or 5 shorted to the black-white on pin 3. If the problem was there only with the relay in place, you probably had the black-blue on pin 8 shorted to the black on pin 6 or to ground (either of which would hold the relay activated).

 

[Wizeman76]

I'm amazed at your knowledge! Yeah there must be a short allowing the relay to stay on. I've basically put in a switch between the red/black wire to allow me to switch it on and off. I think its all down to the switch. There must be something going on in there with the illuminator. I dont know if its completely on or off. Thanks for your help!