81 E21 320i won't start when engine is hot

[biowire]

Having trouble finding the fix to a hot starting problem. Car works like a champ when cool/cold, but after it comes up to temp and everything heats up it will not restart until it cools off. Typically I pop the hood and turn on an electric fan for about 1 hour and its better. When its hot, I don't get a spark.

Any ideas?

Thanks!!

[glotman]

One thing that comes to mind-I have had the ignition coil fail when hot and work when it has cooled down. You can temporarily hook up a spare coil, if you have one, and see if that fixes it.
If not, beg borrow or buy one from someone on the board. I dont have any spare coils left or I'd offer one
Geoff

[davidgoerndt]

Another thing to consider is a fuel system pressure leak causing vapor lock. I've had this problem since I purchased the car. It was hard to start when hot (my temp gauge was at the 3/4 mark). It would take 3-4 long cranks to get any pressure built up to start. I recently replace the radiator and my car runs cooler and as a side benefit it has become much easier to start when hot.

[biowire]

Update, more info.

Swapped out the coil with another used coil. Same behavior. No spark, turns over fine when the engine is up to temp. Let it cool down and it starts like a champ.

I feel like I'm missing something really simple.

[glotman]

ah well it was worth a shot. you may have to make sure the fuel pressure regulator is working as it should. that can also affect hot starting
G