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Thread: Fuel Pump Electrical Diagnosis Help

  1. #26
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    Do you have continuity between pin 1 on the DME plug and contact 85 on the fuel pump relay? If not, there's your problem... grounding pin 1 on the DME has to energise that relay when everything is plugged in...
    '91 Dinan 860 Stage III (soon to be Dinan TT 6L)
    '91 850i 6sp (mint)
    '91 850i 6sp (getting there)
    '90 Dinan 750iL TT stage III
    '94 850 CSi (being restored to factory perfect)
    '94 840ci (4 short - obvious parts car), '91 850i parts car
    '73 3.0 csi, '08 535i, '95 318i
    ...and a few other non BMW cars

  2. #27
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    Report:

    Checked continuity from pin 1 to pin 85 - no continuity. Which begs the question, how does pin 85 get 1.58vdc? Does this wire go through something else on it's way to pin 85? Is 85 getting a partial ground from something else?

    Made a jumper wire, pin 1 to 85.

    Voltage w/o jumper 1.58vdc

    Voltage w/jumper .13vdc.

    Swapped DME's, problem did not move.

    Wow! I'm really lost now. Not that I wasn't before.

  3. #28
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    I hope I haven't stumped everyone. I am totally lost on why this car is doing this. I don't know what do do with it...

    Please help!

  4. #29
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    you have a broken wire. The minimal noise reading you're getting is likely through the EGS unit, which is also tied to that line... forget that.
    The wire you need to trace goes from pin #1 on DME 1-6 to pin 4 (FUEL PUMP Relay Socket #85).
    It isn't a particularly long run, so it should be easy enough to trace.
    You might find it does have a splice (X8036) where the EGS unit ties in, but other than that it is a pretty short hop from the ECU (DME) to the relay socket.
    Brown wire with a Green stripe...

    Your tests above are a bit odd... try this... make a jumper from pin #1 on the DME 1-6 and put the other end directly to contact 85 on the FUEL PUMP Relay socket. Plug the relay in and crank the car, or plug your meter into 85 & 86 and crank the car. You should see 12v across the relay socket on the meter, or see the relay energize with it plugged in. If so, find your break in the wire described above
    '91 Dinan 860 Stage III (soon to be Dinan TT 6L)
    '91 850i 6sp (mint)
    '91 850i 6sp (getting there)
    '90 Dinan 750iL TT stage III
    '94 850 CSi (being restored to factory perfect)
    '94 840ci (4 short - obvious parts car), '91 850i parts car
    '73 3.0 csi, '08 535i, '95 318i
    ...and a few other non BMW cars

  5. #30
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    I think you need to stand back and have a good think of how you got here! In this thread:

    https://www.bimmerforums.com/forum/s...ver!-Maybe-Not

    ...your car was running fine, and that was only August.

    I also think you are poking the wrong pins of the DME and possibly the wrong pins of the wrong relays - that is the only explanation for the results of the tests you have performed so far. A good bit of time spent working out what is where and what your original problem was would be useful - because at this rate you are going to link the wrong parts of the electrical system together and frizzle something in a very expensive way!

    Stand back, retrace your steps and explain how you got from a fully running car to a completely dead one.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  6. #31
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    do both pump work when you apply voltage to the carrier directly??

  7. #32
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    Timm;
    Thanks for the reminder. When the car ran in August, Ithink it was running on 6 cylinders. Why it wasn't throwing a code or something on the display is kind of curious. As for getting right socket, I have a real-deal shop manual and always verify before I jump into electrical as to what is where. I have sone experience with volts/ohms etc, but it goes back 52 years. Rust never sleeps.

    Cartoonz;
    Ran the latest jumper test.
    Keyoff = .07vdc.
    Keyon = .07vdc
    Keyon + crank 12vdc +-

    Gotta wire to replace. Oh joy!

    Seems you are right re: broken wire, but there is no keyon voltage to prime the pump.

    Huh?

  8. #33
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    Update;

    Can someone tell me which harness plugs into DME 1-6 and which for DME 7-12?
    It was plugged in like this. Front harness to DME 1-6, rear harness to 7-12.

    When tracing the brown w/green tracer, I found it going from pin 1 of DME 7-12 to pin 4/85 of relay of 1-6 fuel pump relay vs pin 4/85 of the 7-12 fuel pump relay.

    Is it possible, some PO-S reversed either the DME connectors or the relay bases?
    Could that be the problem?

    Told you this car was boogered up...

  9. #34
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    No guarantees which DME sits where, and it really doesn't matter... but whichever harness hooks to the corresponding relays, that's which side it is... perhaps you've been measuring from the wrong DME?
    That said, I think Timm makes a good point...
    Obviously, what you *thought* was DME 7-12 is really 1-6
    Last edited by cartoonz; 10-17-2017 at 02:10 PM.
    '91 Dinan 860 Stage III (soon to be Dinan TT 6L)
    '91 850i 6sp (mint)
    '91 850i 6sp (getting there)
    '90 Dinan 750iL TT stage III
    '94 850 CSi (being restored to factory perfect)
    '94 840ci (4 short - obvious parts car), '91 850i parts car
    '73 3.0 csi, '08 535i, '95 318i
    ...and a few other non BMW cars

  10. #35
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    I was basing relays, DME's etc. On factory diagrams from shop manual.
    The 0 fuel pressure was going into the 1-6 fuel rail. It may not matter which DME is which, but it may matter which connector goes to which relay. The factory diagram shows, from front to back.
    1-6 fpr
    7-12 fpr
    1-6 DME-relay
    7-12DME -relay
    DME 1-6
    DME 7-12
    EML

    Trying to trace all the brown w/green tracer. The is a 3way splice and a black 4 connector (3 used) with 2 each brown green tracer and 1 brown only.

    If they are connected wrong. I need to figure out what's right, then work from there. It's hard to troubleshoot this when you start with a trainwreck

  11. #36
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    Okay, now that I am checking the correct pin 1 to the correct pin 85, I do have continuity (about 4 ohms resistance). I'm going to try the jumper and see what happens.

    I'll be back...

  12. #37
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    Update:
    Jumper pin 1 on 7-12 to correct pin 85 on 7-12 relay
    Keyoff .26
    Keyon 1.58
    Crank 1.58

    Continuity = yes

  13. #38
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    Back where we started - almost! Crankshaft sensor at the top of the list....
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  14. #39
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    91 Dinan860 & 91 850 6sp
    Crank sensor it is
    '91 Dinan 860 Stage III (soon to be Dinan TT 6L)
    '91 850i 6sp (mint)
    '91 850i 6sp (getting there)
    '90 Dinan 750iL TT stage III
    '94 850 CSi (being restored to factory perfect)
    '94 840ci (4 short - obvious parts car), '91 850i parts car
    '73 3.0 csi, '08 535i, '95 318i
    ...and a few other non BMW cars

  15. #40
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    Groan.....
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  16. #41
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    Didn't want to start a new thread for the same problem, so update.
    Since last time, here's what's been happening.

    2 OEM O2 sensors installed
    2 OEM Crank Position Sensors installed
    2 OEM MAF's installed.
    2 OEM Cylinder ID sensors
    Continuity from pin 27 and 1 in DME's to main and fuel pump sockets.
    1.57 vdc across 85-86 in 7-12 fuel pump relay socket.
    Same problem, new day.

    I have thrown a lot of parts at this with no resolution. I am at my wits end. Any other suggestions?

    Thanks
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  17. #42
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    Can you connect to BOT L and R dmes with software? Try switching the dme plugs around.
    Also does EML light come on during the engine running in LHM?

  18. #43
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    I'm beginning to think I have two separate issues going on.

    First, to answer your question dragon850, yes I can talk to both DME's with GT1 DIS Versions 39, 44 and 57, but cannot with INPA until after I connect with any GT1. Yes, I have swapped connectors on the DME's the problem does not move.

    Second, when this train wreck started, I had a complete "no-start" condition, I had an EML light displayed on the dash. Somewhere in all this, I reversed the fuel lines (as an experiment grasping at straws) and it started and ran on 1-6, which had fuel pressure. I can only assume at this point that I have a DK that is shut down for some reason on bank 1-6 and a fuel pump that is shut down on 7-12, so by reversing the fuel lines, I have now taken the 1-6 fuel line (working fuel pump) and run it into the 7-12 bank which gave me a one sided start and run on bank 7-12, again from the 1-6 fuel line.

    I'm trying to get the fuel pump issue solved before I deal with the EML issue as having 2 working fuel pumps would make it easier to deal with the EML. I hope I explained this so that it makes sense.

    Thanks
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  19. #44
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    Do this, put both fuel lines in 2 coke bottles, then apply voltage(6v 1 amp does it for me but you can go v12) to fuses 23 and then 24. I bet one bottle will start filling with fuel the other one will stay dry.
    This will tell you if you actually have a dead pump.
    I suspect dead throttle or both. Let me know if you need yours rebuilt.

  20. #45
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    Dragon850;

    I know I do have a dead, but not broken pump because I jumpered 30-87 in the socket and I get full pressure, so whatever is going on is not providing ground to 85-86 (trigger voltage).

    The problem is not in the main relay, so I'm still back to square 1.

    Thanks
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

  21. #46
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    Quote Originally Posted by masbury View Post
    Dragon850;

    I know I do have a dead, but not broken pump because I jumpered 30-87 in the socket and I get full pressure, so whatever is going on is not providing ground to 85-86 (trigger voltage).

    The problem is not in the main relay, so I'm still back to square 1.

    Thanks
    Not so fast.... apply +12v to both fuse #23 & #24. Start car.
    Run on all 12?
    Yes - your hypothesis is correct, find why pump isn't triggered
    No - Dead Pump.
    '91 Dinan 860 Stage III (soon to be Dinan TT 6L)
    '91 850i 6sp (mint)
    '91 850i 6sp (getting there)
    '90 Dinan 750iL TT stage III
    '94 850 CSi (being restored to factory perfect)
    '94 840ci (4 short - obvious parts car), '91 850i parts car
    '73 3.0 csi, '08 535i, '95 318i
    ...and a few other non BMW cars

  22. #47
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    I have been chasing this for so long, I really feel like I am just going in circles.

    From the beginning...

    Total non-start condition - discovered during diagnosis and testing
    I have a WORKING fuel pump on 1-6
    I have a NON-OP DK/EML issue on 1-6

    I have a NON-OP fuel pump on 7-12
    I have a WORKING DK/EML on 7-12
    Hence: No DK on 1-6 and no fuel on 7-12 = NON START

    What I did to get it started totally by accident.
    I reversed the working 1-6 fuel line to the working 7-12 bank with it's operational DK/EML
    Hence: I now have a start on one bank 7-12.
    I would like to fix/repair the non-op fuel pressure on 1-6 so I can then tackle the DK/EML issue.
    This is where we are now.

    Cartoonz;
    I probably misread the fuel pump daisy chain and am thinking the fuses are at the bottom - (main relay>fuel pump relay>fuel pump>fuse).
    If I can jumper the fuel pump relay and get full pressure to the fuel line, how will putting 12v on the fuse change the outcome? Does it change the voltage routing? Sorry, I just don't get it. I will give it a try, hell, I've tried everything else, but don't forget, I'm not going to get a 12 cylinder start with the DK/EML issue on 1-6. I guess I would just like to get 12v to the trigger voltage of the fuel pump relay.

    Thanks
    Drives:
    2015 Ram 3500 Dually
    2014 Dodge Dart
    2002 Mercedes Benz SL500
    2000 BMW 528iA
    1998 BMW 740iLA
    1998 BMW 750iLA
    1997 BMW 528iA
    1997 BMW 740iLA
    1994 BMW 540iA
    1994 BMW 740iA
    1991 BMW 850iA
    1990 BMW 750iA (Not an "L")
    1985 BMW 635CSiA
    1967 Buick Riviera

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