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Thread: Help:( Fuel pump no power

  1. #1
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    Help:( Fuel pump no power

    1999 bmw740i. Car died while going 60 mph and had no fuel pressure at rail. Replaced fuel pump but I found out there is no power going to the pump with the key turned or cranking.Any ideas. Also, what is a good manual for this car. Thanks

  2. #2
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    fuse?
    -Rich-


  3. #3
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    Are you getting spark? No spark or fuel could indicate crank position sensor. If you have spark, I would check the pump relay in the trunk. This forum and e38.org is a good resource for most anything you need. CEL light on? Any codes?

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  4. #4
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    The car will start with starter fluid. Checked fuses and switched green relays in the trunk. I'm not sure if that was the right relay to switch. I really need to get a good manual. I disconnected the battery before I checked for codes. My bad on that. from other posts it sounds like the crankshaft sensor.

  5. #5
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    Codes would still be stored. If the CPS is not sending a signal to the DME, there would be no spark or fuel. Also keep in mind, you won't see a good loop at the fuel pump until the car is cranking. It does not 'prime up' with key in pos 1 or 2. This is sometimes misdiagnosed because of that.

  6. #6
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    Can I remove the plug to the crankshaft sensor and see if it still runs on starter fluid? If it doesn't run then I would guess the sensor is good. The old fuel pump worked when I tested it out of the car but it has 160,000 miles so I'm not upset about changing it but I don't feel like changing parts that don't need to be. Thanks

    I'll change the pump relay to eliminate that. Which one is it?
    Last edited by dennybbl; 10-13-2012 at 12:34 AM. Reason: Automerged Doublepost

  7. #7
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    I think you have the right relay. It the next to the last one on the right about the battery. No first hand experience with the CPS. Just passing along what others have experienced. I would personally check for voltage on the larger two wires going into the top cap for the pump, while someone cranks the car. Or I guess you can do the same at the relay before pulling the seat. Just think it would be easier to check there before removing sensors.

    Agreed, no sense replacing parts that don't need to be.

  8. #8
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    i use to hav this same exaxt problem on a e38 of 98 it was the crank sensor but also times wen the pump gets no power there the relay in the trunk u can try jumpin it by puttin a wire on it to put the pump on and then try to start the car but if tht doesent work injecters arent openin cause of crank sensor or the dme is out or ews not readin ur key

    and ya it wil run off starter fluid to mine did the same
    Last edited by jhonmagee; 10-13-2012 at 01:43 AM. Reason: Automerged Doublepost

  9. #9
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    Pop the cover off the relay and give the contacts a poke as shown below:



    The pump should run even with the ignition off - if it doesn't then the problem is with the pump or the fuses up-stream.
    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


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  10. #10
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    You can check the Crank position sensor by metering the resistance between pin one and two. IIRC the resistance should be Approx 640ohm if it is open or in the mega ohm range it is definitely toast.
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  11. #11
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    Oh sure, give him a GOOD answer!

    Good info. Bookmarked.

  12. #12
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    I don't know if u have a 95 or 99 , but if u have a 95 the car needs a crank sensor. If you have a 99 one of the cam sensors mite be broken.. Or there is a issuie with the fuel pump wiring, check the solder points

  13. #13
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    Update. After changing the fuel pump and crank sensor it ended up being a loose ground on the pump relay.

  14. #14
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    Glad you found the issue! Where is the ground?
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  15. #15
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    Quote Originally Posted by dennybbl View Post
    1999 bmw740i. Car died while going 60 mph and had no fuel pressure at rail. Replaced fuel pump but I found out there is no power going to the pump with the key turned or cranking.Any ideas. Also, what is a good manual for this car. Thanks

    Where is that fuel pump relay ground at I have exact same issue as you

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