Hi, I have a 1990 740 GLE with a hot start problem. If I drive in stop and go traffic (the only kind we have in Seattle!) or at freeway speeds on hot days, and the engine gets nice and hot I often find that the car will not crank until it has cooled off, usually 45 minutes or an hour. I turn the key to start, nothing at all. I don't hear the solenoid clicking, nothing after the quiet whirring that I think is the fuel pump, which runs for a half a second or so. All lights, stereo, and accessories work fine, just no starter. I was told that the fuel pump relay and radiator fan relays are identical, and located in the engine compartment in front of the shock mount, so last time it happened I swapped them, with no change. I have not been able to replicate the problem during a convenient time, only when I am supposed to be driving my Mom somewhere or am late for an appointment. Any other relays tied in to the starting circuit that could pre empt the starter/solenoid? I'd like to wait on replacing the starter until I can have some certainty that it is the problem, I ain't made of money!

Any advice or places to check would be appreciated.

Andy

 

During the no-start condition measure the voltage on the blue-green wire that connects to the top of the starter ... That should help determine if its the starter or the other "stuff".

Key position 3 applies battery voltage to this wire.

 

Also, it could be a bad battery or alternator. Maybe the chemicals and plates don't like the hot weather we've been having. The battery should be ~12+ VDC when measured first thing in the morning and ~13.5 - 14.0+ VDC when the engine is running (fed by the alternator). No 12+ VDC implies bad battery and no >13.5 VDC when running implies bad alternator. Check those out. Batteries about 5 years old or so are suspect. If it's the alternator, check out the brushes.

 

Likely a bad starter. Next time it happens rap the starter solenoid with a wooden broom handle. Sometimes that jars it into working temporarily.

 

Thanks, will do. I forgot to mention that I did have the starter and solenoid tested, but it was out of the car and at room temperature, so the fact that they tested fine is probably irrelevant.

So far it seems like the best way to avoid the no start condition is to remember to keep my multimeter in the car. As long as I'm prepared to do some troubleshooting the car runs forever. Maybe I need to disguise the multimeter or sneak it into the car at night. :-)

The battery is less than a year old, it did this before and after replacing it.

I'm definitely leaning towards a bad starter as well.

 

It's your starter for sure. when they go bad they start not working when they are hot first. Does that make sense.