I have a 89 740GL w/4cyl, 8 valve B230F engine, 168K miles. I have a problem that has been occuring intermitantly. If I'm driving the car and happen to stop somewhere and shut off the engine briefly (say 5-10 minutes) the car will not restart. When I first try to restart it, it sounds like the engine isn't firing. If I wait several minutes and try again, the engine fires but will not stay running. If I let the car sit for 20-30 minutes it always starts back up. Also on two occations while driving, the engine just died. Again I was able to restart it after letting the car sit for 20 minutes or so. This has been occuring infrequently for several months but now seems to be occuring more often.

 

Might ba a bad fuel pump relay and it stops working when it gets hot.
They relay is located behind the ashtray and the little cubby,

 

Two more likely suspects, especially if there is a hot no spark problem, are the crank position/rpm sensor on the top of the bell housing, and the ignition power stage.