BMW E30 Stalling And No-Start
This answer is applicable for many BMWs in addition to the one listed below.
car year: 1987
car model: 325is
Randomly my 325is will die. It doesn’t matter if I’m driving slow or going down the freeway. I may have to sit from 2 minutes to 30 minutes before it starts. There seems to be no set circumstance that sets this off. The car may be cool or operating at full temps. This may only happen once a month, or it might take place two or three times in a day. It truly has me baffled.
Unfortunately, we can only diagnose your dying/stalling and no-start issue while it is actively happening. Therefore, you’ll need to be prepared to do some testing when the symptoms occur. See the Fall 2007 issue of our Bavarian Autosport Fast Times newsletter, which contains a DIY article on diagnosing “no start” issues. You will need to use the diagnostic flow path outlined in the article when the engine dies and will not re-start. Once we have some answers on the diagnostic tests (is there spark, injector pulse and the fuel pump running) we can determine further diagnostics. These general steps would apply to any BMW that is having a no-start problem.
With the above points noted, your symptoms do fit into those for a weak main engine management relay or fuel pump relay. If you’re inclined to “throw something at it” I would suggest these two relays. They are relatively inexpensive and may actually fix the problem. If they don’t, we’re back to the no-start diagnostics, in order to prevent any further throwing of parts.
Engine Management, Fuel pump and Oxygen sensor heater relays on E30 chassis: