vsurg

Just did a complete upper end rebuild of my 1986 3.2 L Carrera with the assistance of my retired mechanic. We have been running diagnostics on all systems without success. It starts immediately, cold, but runs about 3minutes before it 'sounds' like it leans out, and stops. We cannot restart it until it cools off. We have checked the fuel pressure with gauge an its fine, even after stall. We have checked the reference and speed sensors and they demonstrate normal resistance. There is 12 V to the injectors both sides. MAF temp is OK. Spark is OK even when it won't start. Grounds are all OK. The Oxygen sensor on the Cat convertor is new. Anybody have any suggestions?

Mlrjr

DME Relay? Buy the solid state version.

vsurg

I replaced that already. Thanks...I forgot to mention that. We also tested the old one, and it was ok.

systemsc

That's the typical problem when the head temp sensor or its connector is bad, i.e. the engine floods. If you still have spark when the engine stops, and you spray carb cleaner into the intake,
and it still doesn't start, the engine is flooded, not "leaned out".

vsurg

Thanks for that. We are going after it again tomorrow and I will pass this on. I know we tested the head temp sensor as well but it was a prime suspect. I will let you know.

systemsc

Next time it dies, just disconnect the temp sensor and jumper the pins with a paper clip. Then try and restart.

Mlrjr

I am having a similar problem. I can go for a long drive and when i come home and shut off the car it will immediately start back, but if i wait 30-60 minutes, it will turn over but not start. Sometimes it will not start until the next day. I have replaced ICV and the DME relay. Also the RPM relay.....it is in the shop as we speak.

prschmn

If it is "leaning out" I'd want to go looking for a vacuum leak-

vsurg

Which pins?

Mlrjr

This might help...

https://www.pelicanparts.com/techart...emp_sensor.htm

systemsc

Remember, it's always a simple process by determining whether it's a spark or fuel problem. Guessing rarely finds the problem!

Mlrjr

Agreed...all were actually replaced before i bought the car based on the records. However the problem has gotten progressively worse in the last month. Its with my mechanic as we type.

systemsc

Really? Then it's back to "square one", right? Sounds like maybe a good mechanic is needed!

Mlrjr

no, i have a great mechanic. The other fixes came before i made the purchase 3 months ago. They thought they had it licked i guess. It was fine until the last 3 weeks. Former mechanic was in Houston. I am in Alabama. Still very frustrating.

vsurg

Update: I have the newer two wire head temp sensor. We replaced it at the time of the rebuild so its new....My mechanic asked me if knew what 'new' meant...he informed me 'Never Ever Worked'. And so it is. The testing yielded an open circuit and hence a bad sensor. Can't wait to replace this with wire intact so as to preserve it's retainability for refund...

Could it be that the reason it starts cold is that the computer stipulates a rich start but that when (after a couple of minutes) it gets no signal from the head sensor, it shuts down sending signal to the injectors?