No start when the car is hot

[ssc25]

I am asking this for a friend that runs circle track, thought somebody might have had this problem before. 90 model Golf, he says its all stock. After a race or practice after the car sits for a few min it won't restart. It acts like its flooded. Everything cools back down, it starts fine. This has bit him twice after a red flag while leading. Any ideas? Thanks, Stephen

[tac911t]

Check the cold start temp sensor. There probably is a seperate one to tell the ECU that the coolant is hot or cold. If the sensor is disconnected (bad wiring) or defective, when the motor is hot, the ECU thinks it is a cold start, and adds fuel, which is too much fuel for a hot start, preventing the car from starting.

[Campbell]

Could be cold start - is he running digifant or CISe? if CIS its likely he has a leaking fuel injector or two. When the car stops the residual fuel line pressure is leaking into the cylinders and flooding the motor.

[ssc25]

its a digifant system.

[Flyinglizard]

Run a fuel pressure hot test. . The down and dirty way is to pull the plugs and let it sit. crank it over and look for a wet cyl. Most likely a leaky injector. If they all are wet, , send them out to get cleaned or buy some E bay ones.
Check the residual fuel pressure. Check the book for pressure numbers, but the running # is about 40 ish, so anything over 20 after 10 min should run OK. IMHO.
pS you can check the temp sensor by disconnecting the sensor . the engine should quit,.

[ssc25]

Got some more info. The car was running under the red flag and started to flood out and it died and then it would not restart. Talked to him last night and he said that he can unplug the coolant temp sensor and it runs (in the shop) better than before. Plugs the temp sensor back in and it starts to run bad again. He is going to try a new sensor. Can he run with the temp sensor unpluged or will it run to lean?

[Flyinglizard]

temp sender is critical for that control package.It sounds bad from here. The inputs are few and all need to work.
MM

[ssc25]

Thanks for the help!! Hopefuly that will fix his problem.

[pfcs]

DIDI II is counterintuitive, esp regarding CTS (coolant temp sensor)!
In fact they usually idle better when you disconnect it and you set timing and check mixture with it disconnected.
Idle switch is VERY important-it and the full throttle switch are paralleled across 2 wires and need checking w/voltmeter w/ign on-this will check that all aspects of the critical circuit function including wiring to ECM!
Setting ignition timing without going thru factory procedure (which includes checking idle swx function and disconnecting CTS) will fuck you up!
If you want more coaching or are interested in the only DIGI II chip that properly fuels an IT 1.8 and raises rev limit to 6700, contact me privately.