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Thread: Fuel pump not priming but works on it's own

  1. #1
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    Fuel pump not priming but works on it's own

    Need some electrical advice. 2000 X1 Lightning. Accidentally let the battery die by leaving the parking light on in the garage for a few days. Battery wasn't able to be recovered, so I bought a new battery. Installed it, and now the fuel pump won't prime (ecm throws a 33, fuel pump short to ground). Fuses are fine, ignition relay is fine (tested with a multimeter), and the pump works when I give it 12V power directly, both at the pump contacts and it's connector (gray and brown w/yellow stripe wires if I'm remembering correctly). Bypassed the bank angle sensor to rule that out. Bike still cranks when I thumb the starter button. It seems like a circuit isn't closing somewhere but I have no idea at this point. Rode fine before I killed the original battery. I have access to the service manual, and I plan on bypassing the clutch and sidestand safety switch to rule those out.
    Any thoughts?
    Last edited by dreygata; 08-20-2019 at 12:01 PM.

  2. #2
    Senior Member Cooter's Avatar
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    If the bike cranks over, it isn't any safety system issue like a clutch or kickstand switch so don't bother with those.

    You are right the BAS interrupts the fuel pump circuit, but IIRC there is a specific fuel pump relay on those, not just the ignition relay (and it would throw that code). If I'm right try swapping them around with the key on and see if it primes.

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    Hm, true about the other safety conditions. I'm just trying to isolate the issue really well.
    I think i tried swapping the starter and fuel pump relay, but I can try again. I know I pulled the fuel pump relay out and tested resistances with a multimeter and it's operation with a separate battery, and it seems fine.
    Is there a way to see if the ECM is supply power/grounding out the connector properly?

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    Yep, the relay uses a small current to control a large current, so it's 2 separate +&- circuits.
    The large current (big terminals) will have one that goes right to the battery (+), and one that goes to the accessory. In this case the fuel pump. Check continuity on both or just put power to the big terminal that isn't (+), and the accessory should operate.
    Jumping the 2 big terminals is an easy way to test the whole big circuit.

    Testing the small circuit is easy too (DON'T jump these small terminals). It needs a (+) and a (-) to operate and connect the big circuit together to turn on the accessory. Either it has (+) on one terminal and the computer sends a (-) signal to turn the relay on (like the fan does), OR it has a (-) and the computer sends a (+) to turn the relay on.

    You'll need to have your meter hooked up to test the small circuit first because when you turn on the key (and run switch) the signal to prime the pump is only on for a second or so.

  5. #5
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    I've already tested the relay, and even swapped the starter and fuel pump relays to see if there was any change. No difference. Bike will crank, but pump won't prime.

    With the bike in the On position, and the engine kill set to "Off', I can switch the kill switch to "Run" and hear the fuel pump relay click. I'm guessing that means the computer is sending the signal correctly, meaning the low current circuit is fine?
    If that's the case, then the problem exists on the large current circuit. Given that I just changed the battery prior to this happening, the problem may exist in the harness between the battery (+) and the fuel pump relay. Does this seem correct?
    You mentioned jumping the terminals for the big circuit. Do you mean removing the fuel pump relay, and using a jumper wire in the socket (corresponding to relay pins 30 and 87) to jump the large circuit?
    Sorry for the wordiness, just trying to be very explicit.

  6. #6
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    Yes, jump 30 and 87. If the pump turns on, that circuit is fine, it's something else.

    If the pump does not turn on with the pins jumped then check for (+) at the 30. If you don't have power there trace it to the battery, if you do have (+) at the 30, check for continuity from 87 and the power wire at the pump.

  7. #7
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    Okay, here's what I've done:
    30 has continuity to the yellow w/ red strip that goes to the sensor, as well as the black wire that grounds to the pump housing.
    30 has continuity to the red (+) wire at the battery. It also will read 13.1V when tested for voltage.
    87 has continuity to the gray wire that goes to the pump
    86 has continuity to the yellow w/red strip wire (sensor), black wire that grounds at the pump housing, and the black (-) wire at the battery.
    Brown w/yellow stripe wire at the pump connector has continuity to the same at the black ECM plug

    The pump itself is reading a resistance of 0.6 Ohms

  8. #8
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    Well, based on the service manual specs, the pump should be 14V operating and draw 3 amps. V=I*R leads me to believe that the pump should be reading 4.67 Ohms, so I'm guessing the pump is bad (despite being able to be run when connected directly to the battery).
    Any thoughts?

  9. #9
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    Also, I'm getting a reading of 6V between the gray and brown w/ yellow stripe wires that power the pump. That doesn't seem right, it should be 12V correct?

  10. #10
    Senior Member rb70383's Avatar
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    Is that 6V across the terminals that goto the pump? If the pump runs when wired hot, but not through the relays, its not getting enough juice. Bad/loose connection or maybe even a terminal at one of the connectors. Is the 6V read at the other sensors since the gray wire feeds all of them? If there is a solid 12V on the gray(grey?) wire, check voltage using a different ground wire, since your using the fuel pump trigger wire...bn/y.


    I'm not sure if you should see 12V across the fuel pump wires with a signal to run the pump. The fuel pump always has 12V. So if the ECM wire is connected to ground at all the pump will run. Circuit complete. IIRC The br/y should not show any voltage. Can you back probe the harness at the pump and see what happens with the key on. The voltage should mirror battery voltage. If so another thing is to measure the voltage drop across the br/y wire when the pump should be running. You should measure no voltage drop in that instance. Any drop means the wire is providing resistance and taking current away from the pump.

    You did hot wire the pump right and it worked?

    Never worked on a tuber, so I'm going by these:


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