Fuel pump not working

Discussion in 'Technical' started by beaver, May 19, 2018.

  1. beaver

    beaver southern zeds

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    As the title says, the fuel pump in my car is not working, its basically a new stock pump, ( after a plenum pull which I have done several time in the past without problems afterward)I've tried the fpcu by-pass nothing, the relay is good, the problem is no power at all to the pump. The engine and body earths are where the should be clean and grounded. The only other thing I've done wile the plenum was off was to replace the nistune board which was socketed by big bob, Some may remember him, with an different tuned eprom. I can't see how replacing the nistune board with another eprom could cause the fuel pump to stop working, but I'm about to put the nistune board back in so i can confirm it. Any ideas?
     
  2. East Coast Z

    East Coast Z Well-Known Member

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    Check the fuse in the engine bay.
     
  3. beaver

    beaver southern zeds

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    Thanks, fuse is good. Swapping the eproms around made no difference, Pump is now running, only because i turned the engine over for maybe 30seconds, the engine didn't start, so I checked the fuel pressure gauge (dry gauge)on the regulator,pressure had built up about 30psi, I hit the starter again, the engine started, had another look at the pressure gauge, pressure had dropped to 20psi, I'm pretty sure the FPCU is gone, also I cant hear the fuel pump prime when I switch it on with datascan, usual I can. This dose not explain why the by pass didn't work.
     
  4. East Coast Z

    East Coast Z Well-Known Member

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    Check the voltage at the fuel pump connector.
     
  5. beaver

    beaver southern zeds

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    Yes I meant to that, i will tomorrow.
     
  6. IB

    IB ?????

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    It might be a basic check but make sure you haven't reversed your fuel lines.
     
  7. beaver

    beaver southern zeds

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    I wish Ian.
     
  8. beaver

    beaver southern zeds

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    So I've been out this morning trying to sort the fuel pump pressure issue, here is what I've found out. To start with I replaced the gauge on the regulator a few days ago, the new gauge is not an aeromotive part, its a half the price job I got of ebay. I replaced the original aeromotive gauge because it came into contact with the + battery terminal (the battery holder had loosened of) which I thought had burnt a hole into the screen. It still seemed to work but I replaced it anyway. The up shot is the new gauge is a pos and is highly inaccurate. This morning when I started the engine the gauge showed 0 pressure, I gave it a couple of taps and it went up to 30psi, I pushed the rubber release button thing a couple of times and it moved up to to 45psi, a few moments later it was back to 30psi, its a pos..The pump connector at the tank showed 11.6 v which I think pretty good at idle.. so its nothing to do with the fpcu or the regulator. I took the car down the shops this morning got a nice carrot cake, wet roads cold tyres not much fun, but there are no problems.
    Wile I was playing round I checked to see I had any vacuum leak, using Stft ltft on data scan, got some solid readings. [​IMG] [​IMG] [​IMG]
     
  9. East Coast Z

    East Coast Z Well-Known Member

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    "The pump connector at the tank showed 11.6 v which I think pretty good at idle.. so its nothing to do with the fpcu or the regulator."

    Perhaps you should revisit your voltage tests.

    One (1) second after the ignition is turned on, you should see battery voltage at the fuel pump.
    If your battery open circuit voltage is 11.6VDC, the battery isn't fully charged.
    If it was, it would read around 12.7VDC.
    It may be easier to diagnose if you use two (2) multimeters, one connected to the battery & the other connected to the fuel pump (both set on VDC).
    You should also see battery voltage at the fuel pump when you're cranking the engine.
    The voltage will drop significantly due to the high amperage drawn by the starter motor, however the voltage at the battery & fuel pump should read the same.
     
  10. beaver

    beaver southern zeds

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    The battery is fully charged, it was on a c-tek wile i had the injectors. The reason the voltage is a little low could be that the cd player came on when I turned the ignition to on for the voltage test. I'll check it again with no other current drain.
     
  11. beaver

    beaver southern zeds

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    Ok checked it again, got 11.9v with every thing turned of. The up shot is i patched into the + side of the of the pump at the connector this time with the engine running at around 2500rpm got 12.8v and at around 5000rpm and got 13.2v. I don't reckon these are exceptionally low readings for the gauge wire nissan used, I know the stock pump will ideally flow around 250lpm at 13.5v and 16psi manifold pressure showing 60psi at the regulator from tests others have conducted, but that hardly every happens because of the wire-resistance factor. Or is the zed an exception, should I be seeing battery voltage at the pump under all circumstances?
     
  12. beaver

    beaver southern zeds

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    LPH not LPM
     

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