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Electric Fuel Pump Failure

Discussion in 'Engines and Drivelines' started by Indycars, Aug 17, 2021.

  1. MMC757

    MMC757
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    I wonder if the pump circuitry has some sort of safety feature that's being triggered, then gets reset when you cycle power.
    Have you verified if voltage is making it to the pump housing itself when its not running?

    It might be a worth an email to the manufacturer for some tech support.
     
  2. Indycars

    Indycars
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    The relay contacts for power are dropping out, so the pump would not be getting any power.
     
  3. PotvinGuy

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    If you want the pump to be on while cranking, it needs to be wired like this:
    fuel pump on.jpeg
    That is, both the operating current (pin 87) and the control current (pin 85) need to come from Always On. If either of them come from Switched Power, then the pump will be off while cranking, since Switched Power comes from the ACC terminal, which is dead during cranking.

    Highly unlikely. Now the system voltage will drop while cranking since the starter draws lots of current (just as an aside, are you using a stock starter? I changed to one of those small geared starters and it made a giant difference; the motor spins faster and the starter draws less current).


    The thing that vexes me now is does the pump and the FP still go off while driving? And why would toggling the pump switch fix it? I've been poring over the schematics and can't find any reason.
     
  4. MMC757

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    What I meant was have you verified this is true or are you assuming it is?
     
  5. MMC757

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    You could install an LED indicating light at the pump to show if its powered or not.
     
  6. Indycars

    Indycars
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    No, it's a PowerMaster mini starter.

    https://www.summitracing.com/parts/pwm-9526

    upload_2021-8-23_13-9-34.png

    Below is my relay board with 4 channels.

    Omron-Relay-Module-5.jpg

    Yes ???? The pump goes off when the starter cranks over, so yes there would be no pressure when I'm driving.

    It's not making sense to me either. Some kind of interaction between the starter and fuel pump relay power contacts ??? Power is still present on the coil, but the power contacts are NOT made.

    Much appreciated !
    .
     
  7. old round fart

    old round fart
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    Can you temporarily leave the relay out of the circuit?
     
  8. Indycars

    Indycars
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    I have a stand alone Hella relay that I'm going to try.
     
  9. PotvinGuy

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    So the pump goes off and then stays off after the motor has started? Or does it come on and then go off while you are driving?

    Whoa! The pump relay has power (pin 86 is ground and pin 85 is +12) and pin 87 has +12 but pin 30 has none? That's a bad relay, as shown in this professional rendering:
    fuel pump relay.jpeg

    ...and the toggling thing fits: the relay is flakey and sometimes makes contact and sometimes doesn't.
     
  10. Indycars

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    The pump stays off until I flip the rocker switch off/on and then I'm OK.

    The pigtail for the Hella relay was labeled wrong, so that took me a few minutes realize. This
    time I went direct to the info on the relay case and labeled the wires myself.

    This did not fix the problem, but it did make it slightly different. Now when I turn the key to the
    Run position, the pump comes on very briefly, less than 0.5 seconds and then goes off. Until you
    turn the key Off and then back to run. I'm getting power from Always On fuse panel.
     
  11. PotvinGuy

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    Time to play elimination. Hook the pump directly to Switched Power; no relay, no switch,, and use a fuse that can handle the pump. After the motor starts and the ignition switch is back at RUN, the fuel pump should go on and stay on. We are now down to the pump or Switched Power as the source of our discontent.
    Drive and see. If the FP drops, check other things on Switched Power (ALT light, voltmeter) to see if they are off.
    I'm beginning to suspect the anti-theft switch or relay.
     
  12. Indycars

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    I put a jumper across the switch in my console and the pump started working. So I went back
    to the relay on the circuit board from the Hella relay and it still works. It's a lighted switch, so
    maybe that has something to do with it. I had already purchased another switch panel, so I
    have some spare switches. With the new switch I can get the pump to work or the light to work,
    but not both.

    It's still mind blowing how the switch would work until the starter was engaged !



    FP04_SwitchPanelInConsole_02947.jpg

    FP04_SwitchPanelInConsole_02946.jpg

    FP04_SwitchPanelInConsole_02949.jpg
     
  13. PotvinGuy

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    Ah, the plot thickens...

    So in one position the pump works and in the other position the light is on?

    I assume you want the light on when the switch (and load) are on? Or light on all the time? How do the other switches work?
    And how do you have the switches wired, i.e. which terminal goes where.
     
  14. Indycars

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    No, I'm not talking about the position of the switch. What I'm saying is when I move the wires
    around on the switch, that's when I can get only the light or the pump to work, but not both.
    Yes, I am flipping the switch during this process and can get only one to work at a time.

    This is the way it's been wired.

    upload_2021-8-24_9-50-29.png

    Yes, that's correct.

    BTW, I cut the old switch open and tested the light from inside the switch. It was
    no good. The light is what I would call a neon light.
     
  15. Rip VW

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    Just a casual observation I noted but the switches you are showing are AC rated switches NOT dc rated. The amperage rating in AC amps is not the same as DC amps. There is a big difference between the two. AC rated switches should not be used for switching DC Loads there to light and won't last long.

    Check out this article about switch ratings... https://www.electronicdesign.com/te...ng-the-right-switch-know-your-ac-from-your-dc
     
    #55 Rip VW, Aug 24, 2021
    Last edited: Aug 24, 2021
  16. PotvinGuy

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    Neon is unlikely, that's for 110 VAC. Yours should be a 12v incandescent or an LED.
    This is the switch insides:
    3 pin switch.jpeg
    But we need to know which pin is which. A common configuration is this:
    3 pin switch.jpeg
    Then pin 1 goes to ground, pin 2 goes to the FP relay and pin 3 goes to the anti-theft switch. Try that and lemme know.
     
  17. Indycars

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    I see what you are saying. They are marketed as a 12vdc switch on Amazon. The lights do work with 12 volts. I cut a used switch open and the contacts look like new. All the switches do is control a relay, so they carry only a small amount of current.

    I do appreciated you reading and pointing out things that might make a difference !

    www.amazon.com/gp/product/B007XXA5HA/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1
     
  18. Indycars

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    I did away with the Impact Switch for now. The starter has been moved to constant
    power, but the fuel pump is still on Switched Power. Don't need the pump while I'm
    cranking the engine.

    My son is out for a test drive, time will tell if I have it configured correctly. Better for
    him to get stranded than me if it quits again !!! LOL !

    #1 - Goes to ground
    #2 - Goes to the relay coil
    #3 - Goes to the switched fuse panel (12v)

    upload_2021-8-24_14-25-50.png

    I guess the looks of it makes me think neon bulb.

    FP05_LightInSwitch_02955.jpg
     
  19. PotvinGuy

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    Ugly little critter. I can't tell if it's incandescent or LED.
     
  20. Island Girl

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    Sure looks like a filament across the top to me . . . of course if it lights with applied power in either direction, that would be a sure way to tell.
     






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