Hot start problems

[adrainham]

Hi, I have a 1988 911 3.2 with a hot start problem. It starts first time when cold but when hot if it is turned off for about 15 mins it has problems starting.

I have changed the Temp Sensor, DME relay, fuel return valve and sent the DME control unit to Bosch and it was returned back with no faults.

Any ideas would be welcome. Thanks Tony

[Sean Smallman]

Try disconnecting the immobiliser.

[sam]

Sounds like you may have a fuel vaporising issue? if you run the car until the engine is hot, switch off, how long after it is switched off before you begin to get the problem?

[adrainham]

Hi about 15mins

[sam]

So you have enough time for the fuel to vaporise and cause the issue, if you leave the motor to cool the engine starts ok? maybe worth checking out your high pressure fuel system.

[tr7v8]

You need to be methodical. When it fails to start you need to pull a plug lead off, pop a spare plug in and see if you have ignition. Otherwise and quite likely you have a fuel problem. Crack a high pressure union and see if you have fuel in the HP circuit. Whilst it isn't starting and you pull a plug is it wet with fuel or bone dry.
Do this and come back to us with more info.

[adrainham]

Thank you all. I will try that this weekend

[adrainham]

Hi Jim,

I ran the engine till it got to running temp and then turned it off and waited 15 mins and connected a spark plug and got someone to turn it over and there was no spark.

[Endoman]

On my 944 S2 and 993 it was the crank sensor, both within 6 months of each other.

[911perv]

Change the crank sensors, they will be at the end of their life by now even if it doesn't cure it. They are a wire coil so sensitive to heat, which is why they work when cold but not when hot