92 325is, Crank and no start issue after reaching operating temp.

[derrty30]

This problem happend randomly one day, and i have been dealing with it for a few weeks now and it is getting very annoying.

Once the car reaches operating temp and i shut the car off, and let it sit for a few minutes, it will crank, but will not start. If i shut it off immediately start it back up, it will start fine.

I did the stomp test and only code that came up was P1111, coolant temp low input reading at radiator, i had a used sensor laying around so i swapped it out but nothing changed, car still gave me issues, I had a spare coolant temp sensor that goes in the head aswell, the blue one that the ecu reads, and that did not solve the issue either, I also had a spare crank sensor, figured id give it a shot, with low hopes of it actually fixing it, and as i expected that didnt solve it either, just figured id give it a shot, took 5 minutes to change.

So my question is, could the coolant temp sensor in the radiator could be giving me the issue? and the spare one that i have is bad to? Or am I just chasing something that isnt giving me the actual issue. coule the idle control valve be giving me an issue? or anything else? Would love to figure this issue out asap. thanks for any input guys!

[dano670]

From what I understand, there are 3 coolant temp switches. 1 on the radiator which controls the aux fan. 1 on the cylinder head that operates the gauge. 1 more on the cylinder head that communicates with the dme. If one is going to give you a problem with starting, it would be the last one.

[derrty30]

From what I understand, there are 3 coolant temp switches. 1 on the radiator which controls the aux fan. 1 on the cylinder head that operates the gauge. 1 more on the cylinder head that communicates with the dme. If one is going to give you a problem with starting, it would be the last one.

I swapped out the coolant temp sensor that communicates with the dme for a spare used one that i had. and it did not change anything. There could be a possibility that both sensors are bad. But the last time i used that sensor on my old engine it worked fine, but that was a couple years ago. When the car is giving me issues, ive tried unplugging the coolant temp sensor and just plugging in the other sensor (not installed in the head) and it will start after a long crank period. I have also noticed a loss in power, and fuel mileage has gone down.

[slocar]

If I was you, I'd start looking at the fuel pressure ...

[derrty30]

If I was you, I'd start looking at the fuel pressure ...

I forgot to mention, when this started to happen, ive noticed my fuel pump was whinning loud, and i had a spare pump from my m3, so i swapped pumps thinking that would resolve my issue. It did not, there is no more whinning though. Think the fuel pressure regulator may be bad?

[slocar]

Could be, though I'm having a hard time wrapping my head around why it would act up only when warm: not exactly a whole lot to go wrong inside an FPR.

Either way, I'd honestly check the fuel pressure while it's running, and then monitor what happens to residual pressure as you turn the car off. I had a similar issue where the car would run (albeit crappy ... it didn't have anywhere near the correct fuel pressure), but once turned off, it would not retain any pressure ... it would just plummet to zero and it would take at least 10 tries to start. New pump solved the issue.

Now as for chances of 2 fuel pumps dying ... unlikely, but they are old, so you never know.

Just my 2 cents.

[Richkid79]

I

[derrty30]

I
ummm, what?

[jsolares]

Could a really bad catalytic converter do it, since that also gets to it's operating temp? other than that i have nothing, really weird issue