Why is my engine flooding

[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]

[nighthawk]

Little unfamiliar with your injection system (i presume it'll be a bosch set up) but it sounds like a cold start fuel mixture problem.

Recommend you check the thermo/time switch (if fitted) and the engine temp sensor for the injection system, if they check out ok. turn your attention towards the cold start enrichment system and auxilary air control.

[Spaceframe]

I think you have the Bosch K-Jetronic CIS (Continuous Injection System)

Your injectors don't have solonoid valves and so inject even when the inlet valve is closed. This is no problem - the system is a good one.

However, the fuel is metered by a plunger in a vertical cylinder which is moved by a circular plate which sits in the inlet air stream.

This plunger can get stuck in the cylinder, especially in the cold weather when the casing contracts...

To cure:

Locate the metering unit (it will have the injector hoses coming out of the top), and in the centre of the hose outlets you will see the casing of the vertical cylinder.
Carefully pour some hot water over this and give it a few sharp taps with a wooden hammer.

Once started, pump the gas pedal so the engine revs gently but with rising and falling RPM. This will cause the metering piston to move up and down in the cylinder.

Go for a drive until you are nearly out of fuel and then put a good amount of redex or other good injector cleaner in you tank. Now have some fun with your engine to get that piston moving up and down nicely.

Eventually this should free it up.

This is the most common cuase of flooding with K-Jetronic.

[Bullseye123]

thanks nighthawk

what does the temp sensor do. i think this could be the problem

[lanciachris]

The temperature sensor unsurprisingly senses temperature.

What this means to you is that when the sensor reports the engine is cold the injection system enriches the mixture with more fuel. Thus if it is a bit fudged, it could be giving it too much fuel causing flooding.

[thesilverfox]

It sounds like the warm up regulator is faulty
as the engine warms up it turns the auto choke off to retain the correct mixture