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Thread: No fuel pump power and tachometer jumping

  1. #1
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    Exclamation No fuel pump power and tachometer jumping

    I'm very new here and don't know the rules but I need help. I have a 1990 535i that will not start. The engine will crank but the fuel pump doesn't get power at all. It worked fine until on Thursday it shut off while driving. The fuel pump relay and dme were just replaced along with the crank position sensor. The only time the pump gets power is when the key is being switched to the first position for less than a second. Also the tachometer jumps around when trying to start the car. Please help, this is becoming extremely frustrating.

  2. #2
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    Did you check the crankshaft position sensor already?
    Using digital multimeter, check resistance between terminals 1 and 2 in crankshaft position/rpm sensor connector.

    Crankshaft Position/rpm Sensor Specifications
    • Coil resistance (approx.) @ 20°C . . . . . . 540 ± 10% Ω
    • Air gap (sensor distance from toothed wheel) . . . . . . . 1.0 ± 0.3 mm (0.04 ± 0.01 in.)

    http://www.bimmerboard.com/forums/posts/1072189/
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    Quote Originally Posted by shogun View Post
    Did you check the crankshaft position sensor already?
    Using digital multimeter, check resistance between terminals 1 and 2 in crankshaft position/rpm sensor connector.

    Crankshaft Position/rpm Sensor Specifications
    • Coil resistance (approx.) @ 20°C . . . . . . 540 ± 10% Ω
    • Air gap (sensor distance from toothed wheel) . . . . . . . 1.0 ± 0.3 mm (0.04 ± 0.01 in.)

    http://www.bimmerboard.com/forums/posts/1072189/

    Thanks for your reply! Also we just put a brand new one of the car. So I do not think that would be the problem.

  4. #4
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    Quote Originally Posted by raydawg22 View Post
    Thanks for your reply! Also we just put a brand new one of the car. So I do not think that would be the problem.
    Your symptoms are screaming that the crank sensor is dying/dead. New or not.
    Off brand crank sensor?
    I recently had one with a new sensor but incorrectly routed wire that was contacting the fan belt and wore through.

    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. #5
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    Quote Originally Posted by ross1 View Post
    Your symptoms are screaming that the crank sensor is dying/dead. New or not.
    Off brand crank sensor?
    I recently had one with a new sensor but incorrectly routed wire that was contacting the fan belt and wore through.
    We bought one from auto zone it worked fine for about 2 weeks then this happened so I assumed it was the crank sensor. I went back to auto zone and told them it was defective so they switched it out for another and the symptoms still continued.

  6. #6
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    Okay so I'm not really sure what happened but I took the GM out and put it back in and the car started right up like nothing was wrong.

  7. #7
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    I strongly suspect this is coincidence.
    What brand is that sensor?

    Another thought has occurred to me. Check the 12v+ terminal inside the right side e-box under the hood. You'll see a fairly heavy red wire that ought to be protected by a cover bridging two studs. The holder unclips and there is a similar connection on the bottom.
    My own car was a no start mystery others had given up on when I purchased it. Lots of parts thrown at it. That connection was loose(don't ask me to explain how)on the bottom. Tightening the nut made the car run again.
    While this is a VERY unlikely scenario it costs only a minute to check.
    Good luck, my $ is still on a bum CPS but hope I'm wrong and all is well now.
    Last edited by ross1; 08-21-2017 at 01:11 PM.

    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

  8. #8
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    The brand is intermotor.

  9. #9
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    Quote Originally Posted by raydawg22 View Post
    The brand is intermotor.
    That wouldn't be my first choice but seems to be working for now.
    If your symptoms re-occur check to see if the engine is losing spark and fuel. Easy enough to do by introducing some fuel(carb spray works well for this)into the intake. If it runs briefly you still have spark.
    Losing spark and fuel together is almost always indicative of a failed crank sensor.
    Your original post didn't give any info about spark or not but the tach jumping tells me the signal from the crank sensor was not correct.

    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

  10. #10
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    Quote Originally Posted by ross1 View Post
    That wouldn't be my first choice but seems to be working for now.
    If your symptoms re-occur check to see if the engine is losing spark and fuel. Easy enough to do by introducing some fuel(carb spray works well for this)into the intake. If it runs briefly you still have spark.
    Losing spark and fuel together is almost always indicative of a failed crank sensor.
    Your original post didn't give any info about spark or not but the tach jumping tells me the signal from the crank sensor was not correct.
    I figured out what the issue was. I saw somewhere that when the tach is jumping there is a bad ground somewhere. The DME relay went bad and someone put the new DME relay into the fuel pump spot and the fuel pump relay into the DME spot. The fuel pump relay was a 4 pin and the DME relay is a 5 pin so the DME relay was not grounded correctly. I forgot to mention I switched them before trying to start the car yesterday and it started right up and has been fine since.

  11. #11
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    Quote Originally Posted by raydawg22 View Post
    I figured out what the issue was. I saw somewhere that when the tach is jumping there is a bad ground somewhere. The DME relay went bad and someone put the new DME relay into the fuel pump spot and the fuel pump relay into the DME spot. The fuel pump relay was a 4 pin and the DME relay is a 5 pin so the DME relay was not grounded correctly. I forgot to mention I switched them before trying to start the car yesterday and it started right up and has been fine since.
    Nice work. It's tough to diagnose when things are assembled wrong, congratulations.

    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

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