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Thread: help e34 intermittently failing to start

  1. #1

    Default help e34 intermittently failing to start

    BMW E34 1995 Sport Auto 525i

    Problem:- Occasionally, once/twice a week having arrived somewhere and switched off car. Locked it, popped into somewhere and gone back to car, unlock it, get in and it won't start. Lock it and leave it for half an hour, then unlock as usual and it starts!

    It sounds like a flat battery, it doesn't try to turn over though and the battery is fine. I wonder if it might be something to do with the immobiliser/central locking system. It's almost as if it is shutting down because the immobiliser thinks someone is trying to steal it!

    Help - any ideas before my wife kills it!!

  2. #2
    Join Date
    Mar 2006
    Location
    Great Britain
    Posts
    446

    Default

    Does it only happen when the engine has run for long enough to warm up?

    If so then I've had this on both a 525 manual and my 540 auto. In both cases, the battery and starter were both fine so do your diagnostics fully before shelling out for something new. I got rid of the 525 but on the 540 I put in a jumper relay to increase the voltage to the solenoid terminal on the starter motor - there was a drop of about 2V in the wiring loom. It wasn't the fusible link. If you do a search on my posts you'll find what I had to do to fix things.

  3. #3

    Default

    Yes it only does it when its hot.

    after reading you posts what did you end up doing. fitting a relay or replacing the ignition switch?

  4. #4
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,249

  5. #5

    Default

    Quote Originally Posted by steve sport
    BMW E34 1995 Sport Auto 525i

    Problem:- Occasionally, once/twice a week having arrived somewhere and switched off car. Locked it, popped into somewhere and gone back to car, unlock it, get in and it won't start. Lock it and leave it for half an hour, then unlock as usual and it starts!

    It sounds like a flat battery, it doesn't try to turn over though and the battery is fine. I wonder if it might be something to do with the immobiliser/central locking system. It's almost as if it is shutting down because the immobiliser thinks someone is trying to steal it!

    Help - any ideas before my wife kills it!!
    This happened to me a few months ago on my 94"/540i and it drove me nuts. It ended up being the cam sensor.
    Good luck
    Fred/Houston

  6. #6
    Join Date
    Dec 2003
    Location
    Australia
    Posts
    494

    Default

    Had this problem myself. It was a worn starter and solenoid.

  7. #7
    Join Date
    Mar 2006
    Location
    Great Britain
    Posts
    446

    Default

    I did replace the ignition switch (and the battery) but that was a waste of money. On the 525, replacing the starter motor was a waste of money.

    What fixed it was putting in a relay to ensure that the starter motor solenoid got the full battery voltage (without the relay some sort of fault in the wiring loom was dropping about 2 volts, which was just enough to stop the solenoid from working).

    Putting in the relay was less time consuming than trying to deduce what/where the actual fault was. I think the fault might have been in the E box but I never got that far.

  8. #8

    Default starting relay

    Hi

    I have a couple of questions about the starting relay.

    pls see attached pic

    many thanks

    steve
    Attached Images Attached Images  
    Last edited by steve sport; 05-16-2007 at 02:18 AM.

  9. #9
    Join Date
    Mar 2006
    Location
    Great Britain
    Posts
    446

    Default

    I've got some photos (I think!) of what I did - I'll see if I can dig them out - I'll hopefuly post them tonight.

    Off the top of my memory, I think the relay was the one that you have numbered 6 (which, rather confusingly, also seems to be embossed on the relay itself with number "3"!).

  10. #10
    Join Date
    Mar 2006
    Location
    Great Britain
    Posts
    446

    Default

    Alas no photos - you might have to wait till the weekend before I get a chance look into this to work out which relay.

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