Problem, it does not start with a warm engine

[kurss]

Hello...
My '91 850 doesn't want to start when the engine is hot.
With a cold engine there is no problem.
Could someone tell me why that happens?

Thank you...

[Fatandre]

The started has gone bad. I had this problem

[kurss]

[CITA=Fatandre; 30942849]El comienzo ha ido mal. Tuve este problema[/QUOTE]

Did you solve it?

[Fatandre]

Yes.
i put in a new starter and problem solved

[kurss]

It is not a starter engine problem, the starter engine works perfectly.

[Fatandre]

It works when it cools down. When it gets hot again it wont turn.

[shogun]

@kurss: please explain more in detail. Does the starter turn in hot and cold condition? But only when the engine is hot, the starter turns the engine but engine does not start?
If so, check both fusible links, a friend had the same on his E31 850 with M70 engine, starter always worked = turned the engine, but engine did not start when it was hot. When it cooled down, engine started again. He changed the ignition switch, as some people recommended, did not help, then he found that one of the 2 fusible links had a haircracka nd that sometimes still worked and sometimes not, he changed the fusible link and problem was solved. Read this, with pics , e31 m70 engine doesn't start, SOLVED fusible links https://www.bimmerforums.com/forum/s...-fusible-links

[kurss]

@kurss: please explain more in detail. Does the starter turn in hot and cold condition? But only when the engine is hot, the starter turns the engine but engine does not start?
If so, check both fusible links, a friend had the same on his E31 850 with M70 engine, starter always worked = turned the engine, but engine did not start when it was hot. When it cooled down, engine started again. He changed the ignition switch, as some people recommended, did not help, then he found that one of the 2 fusible links had a haircracka nd that sometimes still worked and sometimes not, he changed the fusible link and problem was solved. Read this, with pics , e31 m70 engine doesn't start, SOLVED fusible links https://www.bimmerforums.com/forum/s...-fusible-links

Thanks my friend...
The starter motor turns when cold and hot, but when hot it does not start. I'll check the link you sent me.

[Molez93]

I too solved an intermittent hot start problem by having a new starter installed. Dealer tried to troubleshoot it, but just kinda assumed that was the best alternative. Didn't happen again from that point through selling it months later.

[mandd]

So the engine cranks over ok but will not run/start/fire when hot.

Find out what is missing when this occurs, spark, fuel or both.

Some common faults would be;

Crank Sensor

Ignition lead 6-12

Fuel Pump

DME and Fuel Relay

Inline power fuse at right battery cable

Eroded spark plugs

Mark.

Hello...
My '91 850 doesn't want to start when the engine is hot.
With a cold engine there is no problem.
Could someone tell me why that happens?

Thank you...

[kurss]

Thank you all for responding to my issue.
It seems that it has been resolved.
The flat fuse of the right battery was cracked, but also the cables of the crankshaft and camshaft sensors connectors were practically cut, just by touching them to check, several broke. They were completely cracked from the engine's heat after 33 years.
IMG-20240417-WA0000.jpg

[EEDegreeToDrive]

Yeah, I had this issue with my car years ago, the 'warm' engine had nothing to do with it, warm fuel pumps, etc.. it was all about the 'warm' fusible link on the right-side battery that fed the E-box. The test for this is pretty simple, have someone try to start the car, and have someone flex the cables gently-- if it starts right up get yourself to the nearest autoparts store and buy a 50A/80A car audio fuse block. Be aware that the e-box fuse is often the one wrapped in vinyl and is not obviously a fuse.