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Thread: e24 no start problems

  1. #1
    Join Date
    Jan 2018
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    escondido california
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    12
    My Cars
    1987 bmw 635csi 2001 z3

    e24 no start problems

    https://www.facebook.com/photo.php?f...type=3&theater

    ^photo of my ugly beast

    first post on here, and it figures its because I'm having problems. I purchased this e24 as a project a while back. previous owner had it parked next to a storage shed that caught fire and the car got heat damage on the right side, he then parked it for 4 years until I purchased it. according to him it was running perfectly when he parked it.

    it is a 1987 with a manual trans 103k on the odometer.

    what I've done so far.
    drained fuel tank, replaced fuel filter, replaced all plugs, changed oil and oil filter. tested both fuel pumps, in tank fuel pump was bad, so I replaced it. inline high pressure pump works just fine.

    car cranks perfectly fine but isn't getting fuel to the fuel rail.

    where should I go from here? I'm not familiar with these cars at all

  2. #2
    Join Date
    Oct 2015
    Location
    Illinois
    Posts
    120
    My Cars
    740 735 635 535 318is
    If the fuel pumps work and your not getting fuel to the fuel rail, you either have a blockage in a line, or the pumps are not turning on. Test the main relay and the fuel pump relays for operation. You can also try putting +12v into the fuse 11 contact to see if the pump turns on for testing.

    Sent from my SM-G900V using Tapatalk

  3. #3
    Join Date
    Nov 2005
    Location
    Brookfield,CT
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    1,964
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    '92 325IC '88 635
    Fuel pump can work but not necessarily when it's supposed to. ECU looks for engine rotating pulse from crank sensor, then issues fuel and spark. You have two sensors, one to start the ignition process, and one to know that it's running. Check the two plugs at the back of the engine which go down to each sensor/pickup located on and mounted to the bell housing. It picks up the magnet triggers on the flywheel. The sensors are the same but are located in different positions and have similar plugs up top. See that plugs are plugged in and making good connections and that they haven't been tampered with or switched by mistake. Swap the plugs around if you think they may have been swapped, they are not marked. They can also go bad. There is a testing procedure by measuring resistance across the plug contacts. I don't have the values on hand but somebody else might. Also as others suggested , check the main and fuel pump relays too.
    Last edited by carsnplanes; 01-07-2018 at 11:20 AM.
    '88 635, '92 325IC

  4. #4
    Join Date
    Feb 2009
    Location
    Pittsburgh, PA
    Posts
    1,718
    My Cars
    '86 635CSi, '08 128i
    +1 Your no-start is probably the famous Bosch fuel pump safety cut-off. I'd test the speed & position senders for proper resistance. You're looking for a stable 1Kohm between pins 1 & 2 (although anywhere between 750 and 1250 should still work). You'll also need to see very high resistance between pairs 1&3 and 2&3. If the computer doesn't see that position sender signal, it'll never power up the fuel pump relay.

    I always make up a few jumpers with 3-4" of wire and standard spade connectors to test the main and fuel pump relays by the process of elimination. You need two.

    You can use a few short sections of wire as a good jury-rigged solution. I prefer to make a custom set of jumpers instead, I leave a set with each car. You'll need five standard male spade connectors and three short 4-5" sections of 14ish gauge wire. Strip the ends of your wires. To make the main relay jumper, twist two wires together into a 'v' shape, then crimp three spades onto that wire. For the fuel pump jumper, just crimp two spades onto the remaining wire.

    Find the proper relay sockets, remove the relays, then use your jumpers. The main relay needs jumped from socket 30 to both 87a. The fuel pump relay needs jumped between socket 30 to 87. Since the main relay switches main battery power, you should hear the pumps kick on even if the ignition is off....so be prepared for that.

  5. #5
    Join Date
    Oct 2015
    Location
    Illinois
    Posts
    120
    My Cars
    740 735 635 535 318is
    One nice attribute for the late model BMW's is the amount of tech info that can be found on the web. For any new E24 owner, I recommend you download the ETM- electrical troubleshooting manual (wiring diagram), and study it. These are so much easier to get than any GM/Ford/FCA vehicle. Here is a link that these can be downloaded for free....

    http://wedophones.com/BMWManualsLead.htm

    Sent from my SM-G900V using Tapatalk

  6. #6
    Join Date
    Jan 2018
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    escondido california
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    My Cars
    1987 bmw 635csi 2001 z3
    dschart I should have added, I know the lines are clear. I rigged a fuel can in the trunk directly to the inline pump and powered that pump independently. it got fuel to the rail that way so its got to be an electrical problem somewhere. wiring diagrams are a lifesaver, thank you. thanks to everybody for the replies, guess I'm off to start testing electrical.

  7. #7
    Join Date
    Sep 2007
    Location
    Redwood City, ca, USA
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    347
    My Cars
    2015 428i Coupe
    Here's a good troubleshooting guide: http://www.hiperformancestore.com/Motronic.htm

  8. #8
    Join Date
    Jan 2018
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    escondido california
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    1987 bmw 635csi 2001 z3
    idk that is a killer writeup

  9. #9
    Join Date
    Sep 2007
    Location
    Redwood City, ca, USA
    Posts
    347
    My Cars
    2015 428i Coupe
    Yeah, I've used it successfully a couple of times.

  10. #10
    Join Date
    Jan 2018
    Location
    escondido california
    Posts
    12
    My Cars
    1987 bmw 635csi 2001 z3


    - - - Updated - - -

    well found the fuel pressure problem. One of the previous owners of the car moved all the relays around on the fuse box. I finally just swapped them all and now I have fuel pressure.

    still not running though, I am not getting any spark. Is coil failure a common problem on these cars?

  11. #11
    Join Date
    Sep 2016
    Location
    North Florida
    Posts
    111
    My Cars
    1983 633csi, 2017 540i
    I'd check the ground connections under the hood

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