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Hot Start Problem

S

shaynan944

New member
Hi folks, I am in need of some advice please...

I have a 944/1 1985 2.5 lux

She starts and runs fine and gets up to good running temperature but when I turn the car off she will not start up again.
It usually takes 1 hour before she starts again, possibly needs to cool down? I have replaced the DME fuel relay which has not cured the problem.

When the engine is in this non-start hot condtion there does not seem to be any spark?

If anybody has any advise, I would greatly appreciate it.

thanks
 
Hi welcome to the forum. Sorry to hear you are having hot start problems. Its a pretty common problem with fuel injected cars like the 944. Basically if you have substituted the DME relay with no change then its likely to be a fuel delivery problem. When you switch off with a hot engine the system is designed to maintain fuel pressure in the system to prevent fuel evaporation or pressure loss. I would check your fuel pressure is being maintained .Attach a pressure gauge to the fuel rail Run the engine up to temperature then switch off .Monitor the guage. if pressure is being lost then clamp the return hose of the FPR valve on the fuel rail. If that doesn't stop the pressure loss then clamp the hose at the fuel pump. If you still can't stop the leak then chances are you have leaky injectors. I got a cheap fuel pressure gauge off ebay for £10 and attached it with a length of garden hose Oneother thing to check is the engine temperature sensor which controls the cold start injector . I'm sure you'll get plenty more advice tomorrow. Good luck and keep us informed of progress.
 
Hi, thanks for the reply. I'm not sure if its a fuel issue as there is no spark while its hot? Could that be due to either the oil temp sensor or speed sender failing?
 
sorry I didn't get back to you. Yes it could be the crank speed sensor . If the ECU doesn't see 'engine turning' or 'engine running' from the crank speed sensor at over 200rpm then it doesn't ground the DME relay or the ignition system, to prevent fires in the events of accidents. If when you crank you see a slight jump of the tachometer then the sensor is working . Its very slight movement (about 1mph) Its unlikely to be the crank speed sensor or the car wouldn't run when cold . I think its most likely to be one of two sensors giving the ECU the wrong information when hot. Either the engine temperature sensor or the Auxillary Air valve . Also check that the AFM is free to move when the engine is hot.
 
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