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  1. #1
    Ferda's Avatar
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    Fuel Pump Issue FX140

    Hey,

    So I recently went to fire up my ski, long story short found out my fuel pump wasn't turning on with the ski.

    Went through the service manual and checked the relays and everything check out per specs.

    Finally just pulled the pump and hooked it up to a battery, bam, it worked.

    Check the voltage at the plug and it is reading 5.6-6 volts.

    Does the fuel pump require 12V? IF so what I am I missing that only 1/2 the voltage is present????....


  2. #2
    Deanoo's Avatar
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    Check the fuse

  3. #3
    Ferda's Avatar
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    Fuses were checked. I even swapped them with the spares to be safe.

    I even went to the wife's ski and swapped the relays and ECU to double check.

    I feel like I am going crazy here

  4. #4
    TimeBandit's Avatar
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    Yes, should see 12v on the fuel pump power harness connector when you tap the starter button. However, being that the engine won’t run, it will quickly again power off the fuel relay within 1-2 seconds. How / when are you measuring?
    Example: the ski off (standby/sleep mode), attach the volt meter leads to the disconnected fuel pump connector plug (harness side). Should be 0v. Prop the meter up where you can see it whilst you go tap the starter button. Does it jump to +12v for a second or two, then back to 0v ?

    6v only ?? Sorry . . . I gotta ask - sure you’re probing the power plug and not the fuel level plug?

  5. #5
    Ferda's Avatar
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    Yes, I am definitely probing the power plug, the white connector closer to the stern, correct?

    Placing the probes to the connector while the kiddo cranks over the ski, meter propped up like you described.
    0V before cranking. Crank, then jumps to 6V, stays for about 8 seconds then drops back to zero.

    I thought there might be some issue with the connector and cut into the wires and crimped some ends on to the harness. Still nada... But if I take the pump out and rig to the battery, you can hear the pump run.

    I am trying to resit the urge to just hard wire a switch to the battery or borrow some of the neighbors C4....

  6. #6
    Ferda's Avatar
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    Referencing page 7-23 of the service manual, testing the Main Fuel Pump Relay, it only talks about testing for continuity (which passed).

    Should I be also be looking for Voltage? I can't imaging 2 relays being bad...

  7. #7
    TimeBandit's Avatar
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    Hold-off on the C4 just yet ...
    Pump has a black ground wire - which appears to go straight to ground via a harness coupler (joins all ground wires). Can these have issues? Sure. Easy to inspect by popping the cap-connector off and look inside - should be clean.

    However, I'm suspecting Yamaha Security might triggered, because the pump's blue wire goes to the relay contacts, then on to the ECU. So the ECU is the power source because the computer enables power or not based on the ski being locked or not. Hoping you have the FOB key to give the ecu a couple of cycle between locked & unlocked ? Make sure you have your original ECU back in.

  8. #8
    Ferda's Avatar
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    I'll swap the original ECU back in but do the 03 FXs have security measures?

  9. #9
    TimeBandit's Avatar
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    Hummmm ... my memory is flaky that far back. I know the FX does.

    Update:
    Okay, so as I look at the 2003 fiche, it appears to pre-date the Security box stuff we see on other FXs. Well, least that keeps thing simple.

    I found an '03 wiring diagram, yet my copy, it is very unclear (literally a blurry copy) what supplies power on the other side of the fuel relay. Look like it still a blue/red wire heading to the ECU.
    Given you are having issues with both relay's I'm still thinking either a bad ground, or maybe a safety interlock is still engaged, slant-switch, lanyard, etc....

    Tell me ... when you measured the fuel pump connector voltage, did you JUST probe across both pins (black wire, blue wire)? Or did you also put one probe on engine-ground and the other on the blue wire? Or both?

    One last question - hoping to better understand the old FX140 ... where does the yellow wire go from the main/fuel relay? FYI, because the yellow wire on newer models is coming from the Security box and supplies that Mail relay's coil power.
    Last edited by TimeBandit; 06-13-2019 at 12:51 PM.

  10. #10
    Ferda's Avatar
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    Probed across both pins. I didn't think to probe one on the engine but makes since to determine if the ground is bad.

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