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8 Series - E31 (1989 - 1999)

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  #1  
Old 04-24-2011, 02:13 PM
houghtonr houghtonr is offline
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Location: england
 
Join Date: Nov 2006
Posts: 3
Mein Auto: bmw 740i
91 850 - Wont start when hot

I have a 1991 bmw 850 which runs fine when first started. When I arrive at a place say 20 miles away, switch off and wait for a short while, the car will not start. Turns over fine, but no spark, no fuel pump prime. After a varying amount of time (about an hour?) the car will suddenly spring into life as if nothing had happened! The immobiliser has been wired out, because I suspected this. I cannot find anyone with the relevant equipment to read the codes, as the protocol doesn't seem to be the same as any of the modern scanners, so I don't really know WHY there is no spark or fuel. Is it the EML or DMEs that control the spark / fuel, and what provides power to them? Anyone any ideas??
The fault seems to be worse when the weather is hot, indicating a "heat failure" of some component..........
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  #2  
Old 08-12-2015, 05:46 AM
jhobson jhobson is offline
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Location: Ann Arbor Michigan
 
Join Date: Aug 2015
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Mein Auto: 1991 850i
1991 850i wont start when hot

Did you find out the problem with your car not starting while hot .I'm having same issues with my car. I took to the dealer and they said it was a bad fuel pump so I replaced both fuel pumps and still have same issue .
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  #3  
Old 08-23-2015, 02:23 PM
lovemy840ci lovemy840ci is offline
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Location: Southeast USA
 
Join Date: Apr 2015
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Mein Auto: 1994 840ci
Sounds like....

I worked on Domestic models practically my whole life. 30+ years so far. I had this problem with other cars and the solenoid and/or starter was the problem. I always used to replace both since the solenoid was usually attached to the starter. That always solved the problem. But now I'm working on BMW's I don't know if the same rule applies. You might want to test them just in case.

P.S. This only happened to cars with electric fuel pumps. Don't know why.

Last edited by lovemy840ci; 08-23-2015 at 02:25 PM. Reason: Added Info
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  #4  
Old 08-26-2015, 01:04 PM
Motronic Motronic is offline
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Location: Socal
 
Join Date: Jan 2015
Posts: 264
Mein Auto: 750i
Quote:
Originally Posted by lovemy840ci View Post
I worked on Domestic models practically my whole life. 30+ years so far. I had this problem with other cars and the solenoid and/or starter was the problem. I always used to replace both since the solenoid was usually attached to the starter. That always solved the problem. But now I'm working on BMW's I don't know if the same rule applies. You might want to test them just in case.



P.S. This only happened to cars with electric fuel pumps. Don't know why.

No it doesn't because it's got nothing to do with starter.
This problem is sitting here:
1) dme joints cracked, when cold resistance is lower, when hot you don't get the signal at all.
2) dme relay- just old and contacts burned. Replace it first.
3) crankshaft sensor is bad or cracked, therefore no signal to dme
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