technical [E36 M52B25] Help with intermittent crank no start issue

[Reez069]

Hi guys,

This is a strange one and I'm just about dying inside dealing with it. As the title says, the car cranks but does not start. This only happens intermittently. I replaced the spark plugs, battery and the crankshaft position sensor. This only started happening once it started getting closer to winter in Gauteng. When I do manage to get the car started, it drives just fine. No power loss or strange noises or anything. Once it's at normal operating temp I can switch it off and start it 100% of the time. Only once the engine is completely cold does it fail to start and I have to go through the process of sitting there turning the key for 5 minutes. Any ideas?

 

[M3boi]

Check the ground cable on the driver side close to the control arm, I see mine is looking a little dodgy and should be replaced for peace of mind.

 

[Reez069]

Check the ground cable on the driver side close to the control arm, I see mine is looking a little dodgy and should be replaced for peace of mind.

Mine is looking dodgy too so I'll replace it. But surely that would cause other electrical issues, right? Everything else still works fine.

 

[Reez069]

Someone on Reddit suggested I try heating up the engine bay with a heat gun to see if it might be the engine coolant temp sensor. I thought that was ridiculous but I tried it anyway and it started first time. Cheers!

 

[Mytfine]

Check the ground cable on the driver side close to the control arm, I see mine is looking a little dodgy and should be replaced for peace of mind.

This, also a a battery that seemed fine in summer often does not have the required amps when its cold.

 

[Ahmedy]

Mine is looking dodgy too so I'll replace it. But surely that would cause other electrical issues, right? Everything else still works fine.

That's makes 3 of us 😂.
Have you replaced the crank position sensor with an original bmw part .
If you have a spare (bmw) cam sensor you can try it out as well . Reason why I'm saying this, is that if memory servers me correct those leads run close to one another . If you've replaced the one you may have rubbed against the other . That's what happened to me . These sensors and leads are old and crusty if their original . From experience I haven't found any other brand other than the original bmw that worked .
Good luck