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Electric Fuel Pump Failure

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

  1. fletcherson

    fletcherson
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    Hook your multimeter up and see what the voltage does when you cycle the switch... then back trace.
     
  2. PotvinGuy

    PotvinGuy
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    Well, now I can die happy.
     
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  3. PotvinGuy

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    I went back to your wiring thread and see that the Switched Power fuse block is fed from the ACC terminal of the ignition switch (I imagine some dumbo told you to do that). The ACC terminal is normally not hot when starting (I guess so all the juice is available for the starter, but this is not a concern for us because we are clever and use a relay). But it does mean that the fuel pump (which is fed from the Switched Power fuse block) will not have power whilst you are cranking (as opposed to being cranky like ORF). But it is OK because there is plenty of fuel in the carb during the brief moment of cranking. Now can I go back to my G&T, please?
     
  4. Indycars

    Indycars
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    One think I have noticed about this website is there sure is alot of AH namely one that I can't
    mention, but his name starts with "P" and ends with "Y" LOL ! :laugh:

    I found out that I wired the Impact switch directly from power to ground which blew the fuse. It's
    not been a factor from day one. It is serving zero purpose at this time. I did more testing to see
    how the circuit is wired. Below is what I have now.

    NewFuelPumpElectricalDrawing_v08.jpg

    I moved the fuel pump to an adjacent relay and there was NO change in function.

    There was just too many things all happening at the same time that words would not be sufficient
    for this problem, so I did a video. First I test the power contacts of the relay then after it goes
    black and comes back on I'm testing the coil contacts. There is text in the video.


    .
     
  5. old round fart

    old round fart
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    [ (as opposed to being cranky like ORF).

    HEY! I RESEMBLE THAT REMARK!
     
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  6. PotvinGuy

    PotvinGuy
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    Indy, old man, let me see if I truly understand your vexation. Now the motor does start, right? Is it that the pump does not come back on after the motor has started? So the motor is running but the pump is not and the FP is zero? Or have I had too many G&Ts tonight?
     
  7. Indycars

    Indycars
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    Yes, your understanding is correct. To work around this I can flip the toggle switch for the fuel pump off, then back on and I have fuel pressure again.

    Let me add one more quirk to this situation that may or may not have any bearing on the
    problem. You can kinda tell from the video that the starter engages for a very brief time.
    When I turn the key to the Start position the starter engages in a very narrow window and
    then it goes dead again as I continue turning the key CW. Then when I turn the key CCW
    it goes thru that window again and the starter engages again.

    Let me try to put it another way. The Start position in the switch is mainly dead except for
    just a few degrees where the starter turns over and the engine starts. Now most people
    would say, just replace the switch ! I have done so THREE times and every Dorman ignition
    switch does exactly the same thing.

    OK, I decided a video is the best way to demonstrate how the ignition switch is functioning.
    One thing I noticed during the making of this video is the pump continues to run if I don't stop
    turning the key when the starter engages. I continue past the engagement point and then
    backup. If I stop at engagement, then the pump quits most of the time.

     
  8. old round fart

    old round fart
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    It looks like there is a certain spot on the switch contract that works. Very strange. How about trying an OEM switch?
     
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  9. PotvinGuy

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    I never did like ignition switches. But yours, all 3 of them, seem especially evil. I don't think you should be able to turn the switch beyond the Start position. ORF, who has a good idea once every decade, says it: try another brand of ignition switch.

    I once got a fuel filter with male AN-6 threads, but they were actually a few mm larger, and would jam after a few turns on a mating connector. I returned it and got 2 more from the same place and they were also too big! Customer Service got quite gruff with me and just gave me my money back. I imagine they had a bin of the bad filters and didn't bother checking.

    Maybe Dorman made a batch of bad ignition switches.
     
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  10. Spanky

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    I'm with ORF and PG. Try a new/different switch just to verify.
     
  11. PotvinGuy

    PotvinGuy
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    This toggling of the pump switch is very odd. Are we sure the pump is 100% OK now?
    When the pump goes off by itself, do you see other things on Switched Power go off? That would point to a bad ignition switch. It already sounds very touchy and some shock or vibration could scramble it's workings.
     
  12. PotvinGuy

    PotvinGuy
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    Worst case just replace the ignition switch like this:

    ignition redo.jpeg
     
  13. Indycars

    Indycars
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    What does the ignition switch got to do with the fuel pump shutting off ?

    Did you notice the LED for the FP relay stays on even when the pump is not running ?

    This would have been over 3 year period ???

    Actually it was doing this with the old pump until the pump failed. It's also doing it with the
    NEW pump now.

    The relay for my Anti-Theft power goes off. It's powered by the Ign Switch/Acc pole. I just
    looked at the instructions for Ron Francis it is the same way. The gauges on the dash reset
    sometimes, they are digital.

    Note: The power cut-off switch is not there in the drawing below, didn't have room for one.

    Power,Charging&IgnitionCircuitDrawing13a.jpg

    I'm thinking about this switch, but I have to wonder if they are not all made by the same
    company and then repackaged.

    https://www.summitracing.com/int/parts/rfw-is01?retaillocation=int
    .
     
  14. PotvinGuy

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    I have an idea. Does this make sense: when you turn to START you get just a brief click of the starter. Why? Well, when you turn to START the ACC terminal goes dead (as it should) and that in turn cuts power (thru the anti-theft switch and it's relay) to the Switched Power fuse block which feeds the relay that feeds the starter, so that relay drops out and the starter quits. Now if you feed the starter relay (pin 87) from the Always On fuse block that should cure the starter problem.

    The symbol for the starter confused me; the BAT and IGN terminals don't power the solenoid. The IGN terminal operates the solenoid (to ground) and the BAT terminal is connected to the starter by the solenoid when the solenoid is activated.

    If the ignition switch is flakey shock/vibration could cause the ACC terminal to go dead, which would kill Switched Power and everything that is connected to it, including the pump, to go dead.

    So the LED (on the relay board, right?) for the fuel pump stays on but the pump doesn't run. That is strange, since the LED and relay use Switched Power, which is also used for the pump. And you've taken the impact switch out, so it's not the problem. We're getting close to something here. Does the fuel pump have a good ground? To the frame or dedicated wire to a ground bus? I hate frame grounds; they are 50% of the electrical problems I find. The wire from pin 87 of the pump relay to the fuse block: is it firmly crimped and screwed at both ends? Does the corresponding fuse test OK? Might try a different position on the fuse block.
     
  15. PotvinGuy

    PotvinGuy
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    Oh, rats, another maybe thing. The ignition seems to get it's power from Switched Power. But that is dead when cranking so the ignition wouldn't work. Check wiring. The ignition should get power (thru it's relay) from Alway On.
     
  16. PotvinGuy

    PotvinGuy
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    Watched the video and the pump relay LED seems to track with the pump running. It is the second from top on the right hand panel, correct?
     
  17. Indycars

    Indycars
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    OK, I'm thinking (in your words) I've had too many G&T's, besides it's way after 5 o'clock
    in the Burmuda's. Tomorrow morning might be a better time to try something.

    You have giving me much to consider, is there something easy, something I can do with maybe
    a jumper that could point US, or YOU in the right direction ? What should I try first ?

    As always you seem to come to my rescue with my electrical problems .... SO, Many Many Thanks !!!
    .
     
  18. PotvinGuy

    PotvinGuy
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    I would first make sure that the fuel pump, starter and ignition relays (pin 87) get their power from Always On. That should make it easy to crank and start the motor.
    Then driving and watching the fuel pressure. Still don't know what is going on there.
     
  19. Indycars

    Indycars
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    THANKS SO MUCH ! I GREATLY APPRECIATE YOUR HELP !
     
  20. Indycars

    Indycars
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    You were right, the starter now turns over like it should now, there is NO dead spot in the Start Position !!! Thanks !

    I only have two open fuses on the Constant Power panel.
    I have temporary moved the pump and ignition over and that made no difference about the pump shutting off.
    I have the starter and pump on the Constant Power panel, pump still shuts off when the key is in the start position.

    Could it be a voltage spike in the system when the starter engages ?
     






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