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  1. #1

    04 MSX 140 fuel pump ?

    Hi all
    so I got this 04 MSX 140 for free and it starts and runs for a few minutes then starts bogging down to a crawl.
    steps ive taken to resolve issue

    before trying on the water i did this
    compression test 120psi on all three cylinders cold
    replaced the plugs WTF 15$ each

    After trying on the water
    i tested the fuel pump
    at idle 21 psi
    then i pinched off the return line and the pressure dropped to zero psi

    So with this im assuming the fuel pump is failing?

    Thanks for the help and your expertise


  2. #2
    Moderator HiPeRcO's Avatar
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    Welcome to Greenhulk!

    Perhaps a silly question, but did you pinch off the line AFTER the shrader tee?

  3. #3
    martincom's Avatar
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    I have to ask, are you sure you're pinching off the correct line? The correct location is the fuel tank side of the Schrader valve/line. How did you power up the fuel pump? Engine running or other?

    Also, the Champion QC10PEP is a better spark plug, in my opinion, and I have found them, new, on eBay at pretty reasonable prices.

  4. #4
    Haha yup im the newb of the day
    I just went out and tested it again pinching off the correct line after the schader
    Idling 21psi pinched 52 psi

    Im thinking I need to check voltages to see if a aftermarket pump was installed?

  5. #5
    Also thanks for the plug information

  6. #6
    martincom's Avatar
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    Check the current draw of the pump, both when operating normally and the return line pinched off. Disconnect the large, 40 pin connector, from the EMM. Ground pin 40 (brown wire) through your current meter. An OEM pump draws 2.0 amps normally and close to 3.0 when stalled (return line pinched off.) Be careful not to distort or deform the receptacle, within the 40 pin connector, when making your meter connection.

  7. #7
    Quote Originally Posted by martincom View Post
    Check the current draw of the pump, both when operating normally and the return line pinched off. Disconnect the large, 40 pin connector, from the EMM. Ground pin 40 (brown wire) through your current meter. An OEM pump draws 2.0 amps normally and close to 3.0 when stalled (return line pinched off.) Be careful not to distort or deform the receptacle, within the 40 pin connector, when making your meter connection.

    I just went out its going to be a bigger task then i have time for today hopefully i can check it in the morning.
    that plug looks difficult to get to.

  8. #8
    martincom's Avatar
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    If you remove the velcro straps that secure the EMM, you can pull it forward where you can somewhat easily access the plug. There is a socket head (allen) boltthat secures the 40 pin plug that you'll need to remove to extract the plug.

  9. #9
    yes found it and got it all disassembled
    heading to work soon so thats all for today
    tomorrow ill rig up my meter inline on the brown #40 wire for a current test

    thanks again for all the help

  10. #10

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    Quote Originally Posted by martincom View Post
    ... Also, the Champion QC10PEP is a better spark plug, in my opinion, ...
    on the notion of the QC10PEP... I found there are two distinct versions with different model numbers of the QC10PEP...

    Model 958
    Model 7712

    They are both QC10PEP plugs. The only difference is the diameter of the center electrode with the 958 being slightly larger in diameter at 2.5mm vs 2.0mm. Ironically, on one site it states that the heat range on the Model 7712 is a 12 which would technically be a QC12PEP . . I am thinking that is a typo.

    I just installed the 958 and will let you all know how they work out.

    FYI they also make a Model 7919 QC10PEPB which is a "fine wire design" almost identical to the NGK with the gap set at 0.028" vs 0.030" for the other two.

    Also sparkplugs.com is very reasonable on prices.
    Last edited by bfarnam; 08-29-2020 at 01:16 PM. Reason: Added more info

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