car wont start when it is warm outside and worse when engine is warm also
 

My 2002 volvo S80 will not start when it is warm outside and it is worse if the engine is warm.

Starts right up cold.

Never dies if it is already running.

Smells like it is overfueling.

At times the live data shows ect at -40 at other times it show some random erroneous low temp of say between -26 and 30 def F.
Once in a long while it will read to some degree of accuracy.

P0118 present most of the time P0116 Present the rest of the time.

I replaced the engine coolant temperature sensor.

I have the same problem. I cleaned the terminals on the new sensor.
I have checked resistance values and they seem to correspond to the correct temps. Resistance drops as temp increases.

I pulled the ECU and checked resistance across pins A:4 and A:60 at the ECU connector and found no resistance on the GR/R and the BN/SB wires respectively and Im reading the sensor resistance crisp and clear at the ECU connector.

After plugging everything in I checked for vref on the BN/SB wire and I read nothing when -40 is indicated and 0.02v when -26 is indicated.

I removed the ECU and took it apart and I see nothing obvious going on in there. I was not able to identify any loose chipsets or anything like that. No corrosion. Nothing.

I am going to go check and see if unplugging the AC pressure sensor has any effect. But it looks like I might need a new ECU.

Does anyone know of anyone who repairs them. Or can you think of anything I might be missing due to the peculiarities of this mark.

Thanks

Ok well, I had a thought.
Since the ECU is not giving vref, what if I generated a vref for it and spliced in on the BN/SB wire?
Do you suppose it would take the signal?
Does anyone know how many volts vref is supposed to be on this car for the ect circuit?
It would be nice not to have to spend the value of the car just to fix one very simple fault...
Any input would be great...

Could be fuel pressure regulator, pull off vacuum hose on small cylinder located on fuel rail at close front of engine, The Fuel Pressure Regulator vacuum line. If when the hose it pulled off (mine cracks everytime I Try to re use old hose,), Crack in hose is just vacuum leak and that is to be sealed in time if car runs. But if fuel sprays out of nipple connection that the vacuunm hose normally sucks on, then the FPR aka Fuel Pressure Regulators inner diaphragm is ruptured. ANd your car is literally drinking gas through the vacuum line, tune-able><>?

Anyhow I had a car in the desert that would act similar and have a hard time running when it was hot, but could run/jog down the highway when cold out.. Was a 1997 Chevy Cavalier 2.4? Volvo 740 car can have same issue-- Anyhow, the FPR rupturing inside caused gas to suck through hose into intake manifold, enriching mixture, also gas chewed through rubber vacuum hose eventually, which thankfully is how I found it, cause I was like why is there fuel on the head.....thought it was fuel injectors seals, but more careful inspection revealed the vacuum hose leaking fuel. O.o Fixed up the problem. Drove it hundereds miles since.

Agree with DClodgo about the fuel delivery system. Even in your original post, you mentioned that you smelled gasoline.

You have said almost all.. You are obviously good with cars:)

I replaced the ecu. Problem fixed.
the over fueling was a result of the ecu believing it was -40°F. The strategy is called cold start enrichment. The ect input failed somehow internally to the ecu. After installing the rebuilt ecu the engine started without issue repeatedly hot or cold with no issue. Also P0116 codes are resolved.