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  1. #1
    Thad Markham
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    850 won't start then starts hours later gremlin

    Went to a car wash the other day. Shut my 91 850i down and handed the keys to the attendant. The car would turn over but wouldn't start. Had it towed and it wouldn't start at the mechanic. The next day the car started right up. Mechanic had no explination.

    Happened again today. Went to lunch, wouldn't start after. Waited 4 hours then it started up fine. However, when I shut it down in my garage and tried to restart again no luck.

    Any ideas guys.

    Thanks,
    Thad


  2. #2
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    Re: 850 won't start then starts hours later gremlin

    I had the exact same problem recently with a 325 motor. It was definitly temp related and would not restart when hot. For some unknown reason it would start after disconnecting the battery for 15 min. My problem was in my ECU which had a short when warm. I'm not saying this is your problem, but i would start by finding out if when it is in no-start mode, do you have spark and fuel. Might be a faulty temp sensor also. When it does not start do you smell fuel?
    Rick
    91 850i
    87 325is
    90 325ix
    96 Audi A6 & A4
    99 ST 1100

  3. #3
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    Re: 850 won't start then starts hours later gremlin

    Hmmmm, well I don't know what is wrong with yours but I had an '87 535i that had starting gremlins similar to what you describe...plus, it would shut off while driving it as well!!! Turned out to be the main engine control unit.
    I also had a 911 that did the exact same thing your 850 is doing, turned out to be a bad starting relay. I disected the relay and it had an open in the coil wire that was sometimes making contact and sometimes not.
    Like Rick said, you've got to isolate it to gas (fuel circuit) or electric (starting circuit).

    Marty




  4. #4
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    Manos had the same problem and...

    ...he emailed me a few weeks ago that the BMW check valve kits did the trick for him. His 850 starts anytime regardless of how hot or cold it is. So you may want to check that out. Cheap (<$10 for both) and realtively easy to install.

  5. #5
    Manos - Greece
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    check ECU's, fuel pump and crank sensors

    I had a similar problem as ladislav mention before and I want to thank him again for his help. In your case and because you wrote that you had the problem after the car wash, check the box with the control unit. Check if it is closed ok, because if it is not, water can go inside the black box and short circuit the units.

    My problem was from the check valve in the fuel line. But even with this problem It was possible for me to start the engine (pressing the acceleration pedal).

    In my opinion you have to check:

    1. ECU control units (if they have water) or bad relay
    2. Fuel pump or fuel pump relay
    3. crank shaft sensors


  6. #6
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    Sounds like the load-shedding relay is going south


  7. #7
    Thad
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    Re: check ECU's, fuel pump and crank sensors

    It actually wouldn't start before the car wash, so I don't think water is the problem. Thanks so much for the other suggestions.


  8. #8
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    Is it Automatic or Manual? If Automatic can you

    try to start it in Neutral? What does the gear selection display show when it is in Park?


    Click to join DCMETRO_E31

  9. #9
    Thad
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    Re: Is it Automatic or Manual? If Automatic can you

    it is a manual.

    Thanks

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    You could try reading the fault codes


    I had a similar non-start problem when my under floor wiring harness got wet (windscreen seal). I dried it out promptly, but the engine wouldn't start until the next day. It did crank OK - just wouldn't fire.

    At the next service the mechanic read out some faults indicating the "code" security lock prevented some starts (a MID feature I've never used, but the timing did match up with the wet wiring event).

    Anyway, the fault codes are there to assist diagnosis - it'll probably be cheaper to have them read than to replace items by guesswork.

    searbc.

  11. #11
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    Member No: 22936 Scohen is an unknown quantity at this point Scohen's Avatar
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    I have copied (from the archives) a solution to the same problem when it happened to me .

    You can look it up by searching "load-shedding relays."

    For YourFuture Reference ......
    I had a problem with my 8 these last couple of weeks.

    Symptoms:

    -Turn the ignition switch - car would not start
    -Idiot lights would not light except for the SRS
    -Cabin lights would work
    -windows and sunroof would go up or down when key was inserted into
    door lock
    -sometimes it would only take a minute or two for the idiot lights
    to come on and the car would start
    -Other times over a half hour grrrrrrrrrr

    Thought it might be the "tail/switch" portion of the ignition switch

    No Joy

    Eventually tracked the problem down to the "unloader relays" K9 and K61

    These relays turn off the power from large draws of electricity during the starting procedure.

    I was familiar with another term for this type of relay: "load-shedding relay"

    Replaced both relays $24 and the car runs perfectly.
    Last edited by Scohen; 03-25-2011 at 11:47 AM.
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