1987 325is hard start when hot/warm

[flipwils11]

Did some searching on the forum and this thread told me a lot and a place to start. But I want to confirm for sure.

http://www.r3vlimited.com/board/showthread.php?t=266776&

Our 325is 5spd starts right up when cool but after driving somewhere or if it is a new start (but has been sitting in the hot sun outside) it's really difficult. I can usually get it to start with 4-5 seconds of cranking and my foot nearly to the floor but if it doesn't catch on that first attempt I'm stranded for 15 minutes or so before I can try again,

From that thread, if I wanted to just try parts swapping vs troubleshooting I could go with a new cold start injector and a temperature sensor, does that seem accurate? Which one is the temp sensor I need to swap, one of the units in the thermostat housing?

[dnguyen1963]

Do a smoke test when the engine is warm. Plug both exhaust and intake.

[NoM54me]

So, it's difficult to start if there's any heat in the coolant above the outside air (ambient) temp? If you have an I engine, you don't have a cold start injection system like the OP in the thread you referenced does...he has an eta engine. The coolant temp sensor is at the rear of the thermostat housing, and should have a blue connector. This part is very important, tells the ECU how much fuel to inject based on operating temps. Your idle air control valve could be failing, or fuel pressure regulator, failing fuel pump, etc. There are a handful of problems associated with your symptoms. Get a Bentley manual...or even a Haynes...and a decent multimeter, start going down the list. You shouldn't need to touch the accelerator at all to start the engine. Are there any idle/running/driveability problems?
I've always found this link to be helpful:

http://www.hiperformancestore.com/Motronic.htm

[flipwils11]

Thanks, didn't realize that other thread was an eta engine. There are no driveability or idle problems once it's started.

I also wondered about the fuel pressure reg.

[TobyB]

Needing to open the throttle to get it to start's a classic symptom of
leaky injectors. It's actually really easy to test for- put a pressure gauge
on the fuel rail, and see if it holds fuel pressure after you switch off.

There are other ways to lose pressure. and dozens of other things that can
cause hard hot starts, but if it's cold- starting OK, ruling out
the injectors first is quick and easy, and they can hurt your engine by diluting the oil.

hth

t