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Thread: 1995 540i fuel line diameter

  1. #26
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    fuel pump relay is served by the DME relay, start there.
    Does it have spark when cranking?

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  2. #27
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    fuel pump relay gets power though, and gives power to the cooling fan and fuel pump through the green violet wire. in my case it exits the relay but doesnt reach the fuse box at the other end. check out the pic fuel pump wiring.png

  3. #28
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    ugh... felt pretty dumb after realizing two different wires are the same colour, still working on it, now I am getting voltage... close but still no cigar

  4. #29
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    pin 86(red/wht wire) at the FP relay should see 12v+ from the DME relay while cranking. If not connect a test light between the brown wire corresponding to pin 85 on the DME relay and 12v +, when cranking the light should glow, if not no signal from the DME for fuel/spark. Probably because not seeing engine rotation from the crank sensor, IE dead crank sensor

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  5. #30
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    well I am making progress... I jumpered the pump relay and I get voltage at the pump now... but it doesnt seem to run... at least I dont hear anything and there is no gas coming out of the fuel line at the engine. seems like the pump is dead... will go to bimmer heaven and get one

  6. #31
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    just one quick question - we ran into an arguement at the shop as to how the program is stored in the computer. is it a tape, hard drive or something else?

  7. #32
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    You mean the engine tune? Volatile* solid-state memory on transistorized circuits, a la computer RAM.

    *Means that it needs a constant supply of voltage to remain active, unlike a hard drive or the basic engine software. That's why disconnecting the battery resets fuel trims and such.

    Tape
    Last edited by moroza; 09-30-2018 at 08:59 PM.

  8. #33
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    Bosch 3.3 DME

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  9. #34
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    Hello there. Back to working on this thing. I measured for voltage at the fuel pump connector and it is within spec. took the pump out, attached it to a battery and put it into a tub of water, the pump shoots out water. when i put it back into the car, there is only a slight gurgling coming from the pump area and nothing else. all the in car tests have been done with the pump relay removed and a jumper instead of it. I have the pieces, but when i put things together it doesn't work! has anyone been in this situation? any help appreciated.

  10. #35
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Basic: is there fuel in the tank?

    Advanced: Test for voltage at the pump connector while it's running. You may have damaged wires that test ok at DMM current levels, but are kinked or otherwise messed up to the point of dropping too much voltage at pump draw levels.
    Last edited by moroza; 10-26-2018 at 12:16 AM.

  11. #36
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    hmm that seems like a good idea... will check that right now. as for fuel, yes there was a couple of inches of gas in the tank when I was taking the pump out

  12. #37
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    Quote Originally Posted by vroomZOOM View Post
    Hello there. Back to working on this thing. I measured for voltage at the fuel pump connector and it is within spec. took the pump out, attached it to a battery and put it into a tub of water, the pump shoots out water. when i put it back into the car, there is only a slight gurgling coming from the pump area and nothing else. all the in car tests have been done with the pump relay removed and a jumper instead of it. I have the pieces, but when i put things together it doesn't work! has anyone been in this situation? any help appreciated.
    Your gurgling tells me the pump is cavitating, sucking air. Put some gas in the tank.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  13. #38
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    ok so now ive found it... checked for power at the fuse, test light lights up good, checked with a test light at the fuel pump plug and its very dim. does anyone know any points where the wire might break or where it runs? thanks

  14. #39
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Green/Purple wire begins at the fusebox, goes through the firewall above your left foot via a large yellow connector, down along the left rocker (inside the car), into the rear seat area from the left, back out of the car behind the battery on the right through a grommet*, near but not shared with the right rear ABS cable, above the subframe, then above the tank to the fuel pump. There are no splices; the yellow connector is the only one.

    *This and back are where I'd look first. Stick your test light on the wire just before it exits the interior, make sure you have a good contact, and see if it's bright there. Yes? The break is further back, as expected. No? You have bigger problems.
    Last edited by moroza; 10-26-2018 at 02:43 PM.

  15. #40
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    The wire break would usually be within 1 foot of the pump's connector.

    Hey...Wait a second that might not be it at all. It could be your female pin at the connecter, or the wire just behind it. Test the wiring just one inch behind the connector first.

    In fact pull the connector's boot back fully and look at all the wires just behind the plug. (like half an inch). You're going to see stripped insulation. Actually that insulation has burned off and wires are touching etc. The solution is simple. Take fish tank clear tubing, cut a short length, cut down its length and insert it over each wire with needle noose pliers. and squeeze it into the back of each connector. You get the drift.

    Unless of course you can easily separate the wires and redo the insulation up to the connector's back with tape. The space is pretty tight.

  16. #41
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    ok, so i have checked for power just behind the battery, and its good there, but nothing at the connector, where do I check now? thanks

  17. #42
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    Quote Originally Posted by alang1990 View Post
    The wire break would usually be within 1 foot of the pump's connector.

    In fact pull the connector's boot back fully and look at all the wires just behind the plug. (like half an inch). You're going to see stripped insulation. Actually that insulation has burned off and wires are touching etc. The solution is simple. Take fish tank clear tubing, cut a short length, cut down its length and insert it over each wire with needle noose pliers. and squeeze it into the back of each connector. You get the drift.

    Did you do this?
    Last edited by alang1990; 10-30-2018 at 12:03 PM.

  18. #43
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    yes I did. now I think it might not be the wire at all, but rather a bad ground at the tank? I ran a new wire and it still gives me the same result when I ground at the tank. when I ground at the spare tire bolt though, it works.

  19. #44
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    The tank itself isn't really grounded to the chassis. The fuel pump ground is inside the cabin, under the rear seat.

  20. #45
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    Quote Originally Posted by mrgraybeard View Post
    The tank itself isn't really grounded to the chassis. The fuel pump ground is inside the cabin, under the rear seat.
    So op you have a ground wire that goes from the go connector to the abovementioned ground point. Check continuity between both.

    Watch some YouTube videos on to to check continuity trace wiring breaks etc.

  21. #46
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    well it now seems that the wiring issues are resolved, but now the pump doesn't work. I took it out of the tank and attached it to a battery, nothing. how is this that the pump was working one moment and then suddenly stops? I hope I haven't fried it? thanks

  22. #47
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    so i wanted to hear the engine run so I tried connecting a fuel injector cleaning pressure tank to the fuel rail and I turned it up to 50 psi. tried cranking the motor, it cranks but doesnt even try to fire. what is happening now? man this car is frustrating. will try to install ISTA and diagnose it, will any errors show up or not?

  23. #48
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    Hang in there; best believe this car at 23 years is a lot easier to fix than a new one will be in 23 years.

    Lacking an obvious thing to try, do the traditional check for spark and fuel (injection, in this case, not supply): remove a sparkplug, keep it in its ignition coil, ground it to the chassis with a jumpercable, crank and see if 1. it sparks, and 2. if fuel shoots out of the cylinder. Try to keep the plug away from the cylinder and the test length to a minimum, for fire hazard reasons.

  24. #49
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    ok so although its freezing out here I have tested for spark, and i could have probably seen it from 50 feet away. there was a clear bright spark. will check with a noid light for the injectors opening. if anyone has any ideas let me know.

  25. #50
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    Ok so i have checked for the injectors opening, and they do... hmm... seems like I am missing something but I am close to getting it to start. any ideas?

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