Can you solve this one?

[Bullseye123]

I really need your help here.

I have a 1987 Porsche 911 3.2L
When I start the car from cold it runs for about 20 seconds then stalls with a smell of petrol. The engine will not restart. Wait 15 minutes and same problem. This happens about 2 out of every 5 starts.
I have disconnected the immobiliser, replaced the DME relay and checked the fuel pump.

Any help would be greatly received.

[e-mail]

[christians]

well i would try to prove that it is the spark you have lost by getting sombody to crank the engine when you observe the ht lead. if this is the case i would check the reference sensors (2) located on the left hand side of the bellhousing , you really need a scope to check the pattern of them. one is for tdc and the other is for rpm. the air gap between the teeth should be .7mm +/-.2 and is adjustable,Although the symptoms you describe are not totally comesurate with sensor failure. if there is a spark at the ht leads the sensors must be ok as they tell the dme that the engine is turning and therefore fire the injectors and the ignition coil creating the spark . i presume that the usual suspects are in good order.disributor cap/rotor arm/ignition leads spark plug end caps and the engine runs well when it is going.
hope this helps a bit.
regards christian.

[ninemeister]

If you can smell petrol the engine must be running excessively rich, so provided that the immobiliser or alarm has been disabled, you probably have an engine temperature related problem.

The only link between the ECU and the engine related to temperature is the cylinder head temperature sender which is located on the back of #3 cylinder. Common fault on the Carrera 3.2, the later replacement senders are two wire and more reliable.

To diagnose it you need to measure the resistance to ground when cold and immediately after the 20 seconds the engine runs, cannot remember the ohms cold through hot but it is in the manual.