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engine wont switch off

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deanobeano

New member
Ok, I have a 1989 F plate 2.7 944 lux.
It starts fine but when i switch the engine off and remove the key the engine does not stop but keeps on running. Its as if it hasnt realised lol Is this the ignition switch at the back or maybe the stop relay?
 
My money would be on the ignition switch mate. I take it you have to disconnect the battery? What happens with the dash board when you recoonect the battery?
 
This is either an electrical fault or a mechanical one. If its electrical then could be the mentioned relay. Although not knowing about these cars in particular i could be wrong.

Mechanical fault though, has it been smoking much? Leaking valve stem oil seals?
High amounts of oil in the combustion chambers could cause hot spots around the plug and cause the engine to run on without ignition.
 
ORIGINAL: Christoff

This is either an electrical fault or a mechanical one. If its electrical then could be the mentioned relay. Although not knowing about these cars in particular i could be wrong.

Mechanical fault though, has it been smoking much? Leaking valve stem oil seals?
High amounts of oil in the combustion chambers could cause hot spots around the plug and cause the engine to run on without ignition.
Click to expand...

not without a fuel supply it can't .[;)] the Motronic fuel injection system has various safety features built in to prevent the car catching fire if involved in an accident . Without the DME relay activated the fuel pump can't pump.
Something is preventing power being disconected to the ECU and the DME relay is staying energised supplying power to the fuel pump and ignition system.
As Rob says pound to a penny its a faulty ignition switch. Have you tried wiggling the key when switching off ?
Be careful when fiddling with the wiring to the switch as there are constant live feeds direct from the battery which can only be disconnected by removing a terminal at the battery.

I would leave one battery terminal loose for quick removal in case you have a short. Don't worry about your battery being disconnected as the engine management (ECU) has a non volatile PROM which retains all data in event of a loss of power.

I'd look at the immobiliser as wellit could be providing an indirect 12v+ to the DME relay.

For now you could pull the DME relay which will shut off the supply to the fuel pump and ECU but it won't take too much of that without failing.
Better to use a 3xway bypass with a switch built into the 3xway bypass wire from terminal 30 of the DME relay socket.
 
Well ive finally go back around to fixing the problem after the cold snap and when i disconnect the battery etc it just keeps on going which i suppose it would via the alternator. I onl stop it by pulling of the ht lead. No smoke from the rear though and oil pressure is excellent. Mind you there is a large button by the side of the steering column n looks as if someone has fitted it there so im wondering if the prev owner had farfed about with fitting an electric start or something.So I have bought a new ignition module for behind the switch at a lovely cost of fifty quid and gonna try that this weekend. Fingers crossed.
 
Dean I suspect that your imobilser is the problem.
Most of them are connected to the fuel pump relay (DME) and work by isolating the ignition and fuel pump.

If the fuel pump wasn't pumping fuel it would be impossible for your car to run-on for long after ignition switch off. Therefore it has to be a rogue supply from either your ignition switch or DME relay or immobiliser.

Are you sure that no-one has connected anything electrical in your car recently like a CD player or immobiliser ?

oh forgot ...it could be a faulty ignition switch, have you tried wiggling the key after you turn the ignition switch off?
 
I don't know wherev the fuse box is in these cars but I once had a BMW and a short developed in the fuse box.
 
yes I suspect that is quite common on 944. The fuse/relay box is on the scuttle under the bonnet nearside and hangs over the passenger footwell. Its the favourite place for connecting an immobiliser as the relay /fuse connections are visible from the footwell behind the glovebox..

 
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