1992 535i TAKES THREE CRANKS TO START WHEN HOT

[kristyrick]

This is the second summer that this problem has occurred. In late fall, winter, and spring the problem does not exist. I live in upstate NY and it is quite cool that time of the year. As soon as the days get hot this problem appears. In the morning the engine will turn over with one crank and will run smooth. If I then run the car and park it for 1-3 hours the engine will take three cranks to turn over and will idle just fine. Note that if I park the car and start it within a half hour or so the engine will turn over on one crank but not smoothly. In all cases once the car starts it runs perfect. This problem started last year and disappeared around October and reappeared in June.

I had a local mechanic who specializes in BMW's take a look at the problem. He checked the fuel pump relay and replaced the crank position sensor. After he completed the work the problem still existed.


I am convinced that the problem is heat related. Is it possible that a sensor is not sending the computer the right information on the fuel mix when the engine is moderately hot. I'll let my mechanic have another try at it before I take it to the BMW dealer. Any insight or ideas would be appreciated.

[Jeff N.]

Sounds like leaky injectors to me. It's the hot start with rough idle that suggests that to me.

It could also be a problem with maintaining fuel pressure via a bad checkvalve in the fuel pump. However, that wouldn't lead to the rough idle on hot start. Still, it's a cheap fix. Check BMWE34.net for the check valve fix. About $10.