Hot=will not start
 

Vehicle starts and runs normal at operating temperatures.
If I try to start once hot, vehicle will not start until it cools.
Engine cranks but will not start.

I cleaned grounds, replaced LH with know operating one and still not good.
Anybody had this situation, any ideas what can be causing this issue?

How long does it have to cool?

Vapor lock?
Temp2 sensor
really bad leaking FPR/Damper diaphrams?

Are the plugs wet after an attempted hot start?

Bad Temp2 sensor (worn in hot range)?

These are also symptoms of thrust bearing failure. What year is your car, and is it standard or auto?

[QUOTE=Speedtoys;17531325]How long does it have to cool?

Vapor lock?
Temp2 sensor
really bad leaking FPR/Damper diaphrams?[/QUOTE


​The vehicle cools for approximately 15-20 minutes

The vehicle is auto 1986. Thrust bearing failure.??

What are resitance values in hot range?

Michael,

If you have a problem with the diaphragm on one of either the FPR or dampers when you switch off the engine the fuel rail will lose pressure quickly and with the heat soak present the fuel can vapourise inside the rail and then the car will not start until the thing cools off and the fuel condenses once more. Cranking the motor theoretically should reinstate the pressure but i suspect being at a high point in the system the vapour gets high point locked and does not wash out. Similar thing if an injector is leaking

If opening the bonnet sees the problem resolve itself "quicker" that might confirm the above.

i doubt it is a TBF issue but then you should know for a fact such is not happening and if that is not the case then you need to ensure you know for a fact that all is well.

Appreciate everyones help.
Thanks

​​​

TBF not very common in '85/'86 engines.

Dampers/regulator should be the first place to check....super common.
And even if the dampers aren't leaking, most of them no longer are able to move, due to the diaphragms getting rock hard. This causes severe pressure waves in the fuel rails...resulting in both lean and rich running conditions.

928 International sells my fantastic reproductions, if yours are leaking/old.

This exactly what happened to one of my 86 cars and it was a loose/broken wire on temp sensor 2.
This incorrectly tells the LH unit that the engine is cold [because it isn't getting the signal] and it richens the fuel mixture for cold start.
Re-soldered the connection and never had another issue.

Hot engine about 200 ohms
Cold engine about 4000 ohms.

This is what Greg's new HW looks like, installed.

Tucks nicely into the rear as well.

https://cimg4.ibsrv.net/gimg/rennlis...5c5a0c0a9.jpeg

I had a very hard to diagnose similar issue - would not restart and run after fully warming up but would start & run fine from cold.

After lots of work turned out to be the ISV that was sticking closed only after the engine had heated up - I was surprised it worked that way around. On the bench it had tested out fine - if not it would have been swapped out for diagnostic purposes sooner.

Alan

Good morning Bimmermike. I once had the exact same issue with my 87 S4/ 5 speed. It was nothing more than a faulty fuel pump relay. Start with the simple stuff first. I got stuck more times than I care to remember. It hasn’t happened since I replaced it.