E36 fails to start when it is at operating temperature - United Bimmer Community

**grahamw** · 09-14-2010, 08:00 AM

Any clues on the following please? It has got me a bit stumped! My car is a 1995 E36 320i sedan. Nice machine. Done just over 200k km. No problems so far. That is up until several months ago when a seemingly intermittent fault started to appear. The starter motor fails to engage when the car reaches operating temperature - but it doesn't happen every time. Only intermittently - and generally when it is the most inconvenient time. All other systems and circuits work fine. Some of the things I have done to try to overcome this problem include replacing battery, checking and cleaning all earthing points, new alternator [slip rings were worn out anyway so that had to happen regardless]. Cleaned starter motor connections. None of these made any difference. I initially thought that the starter solenoid might be at fault but that works fine when the car is cold or below normal operating temperature. Checked all fuses - all ok. Replaced oxygen sensor relay which interestingly seems to have reduced the frequency of failure events. This same relay is listed as the start detector relay on the M3 model which seems to be a bit of a coincidence. Maybe there another faulty relay that is playing a part in this little drama? This relay is quite warm to handle when removed at the time of a failure. Let it cool down by putting it in the fridge for maybe 10 minutes - put it back in and the car starts fine. Help!!

**grahamw** · 09-29-2010, 08:22 AM

An update...PROBLEM SOLVED!!!
the fault was eventually tracked to a significant voltage drop across one component of the car's immobilizer unit. Isolated that and we are now rollin' with no more warm start issues. This one had me stumped for a while. Thanks for a great forum. Be in touch soon.