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  1. #1

    Exclamation MSX140 running inconsistently

    I've had this '03 MSX140 for a couple years now, but never ran good. Sometimes the ski starts and quickly dies when revved.
    I changed plugs, old gas and oil. Then it ran good on trailer while testing. Now it wont kick at all. Any suggestions?

  2. #2
    martincom's Avatar
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    We'll need some more symptoms to assist:

    • Cylinder compression
    • Fuel Pressure at the Schrader valve (tire valve in appearance)
    • DC voltage on white/red wire at injectors, with everything connected, while cranking & while running
    • Any RPM indication on MFD while cranking?

  3. #3
    Quote Originally Posted by martincom View Post
    We'll need some more symptoms to assist:

    • Cylinder compression
    • Fuel Pressure at the Schrader valve (tire valve in appearance)
    • DC voltage on white/red wire at injectors, with everything connected, while cranking & while running
    • Any RPM indication on MFD while cranking?
    Compression: #1, 8.75lb, 125kg
    #2, 9.0lb, 130kg
    #3, 8.5lb, 120kg
    Cranking shows 300 rpm
    Shrader valve apparently removed by original owner who did some other mods on it the girl I bought it from said. Need to install new one and test pressure.

  4. #4
    martincom's Avatar
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    Your compression numbers are low, but consistent across all three cylinders. So I'm not too concerned about that.

    The MFD indicating 300 RPM, while cranking, tells us that the CPS is sending signals to the EMM and the EMM is functioning--at least partially.

    If you dribble a small amount of gasoline down the throttle bodies and then crank it, does it attempt to start?

    Do you have spark at each cylinder?

    It was a somewhat common failure for the Schrader valve cores to work loose from the bodies, on the MSX140s. So I'm not surprised it is not in place. I'm speculating it was a manufacturing problem with a particular lot that made its way to the MSX production line.


  5. #5
    Engine fires up with gas dumped in throttle body.
    No pressure/gas at schrader valve location

  6. #6
    radio-active's Avatar
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    Fuel pressure regulator has fallen off the pump assembly and is lying inside the housing.

  7. #7
    martincom's Avatar
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    Ditto radio-active's reply. See this thread for details as to how to repair and reinforce it. You're in for a bit of a job. The steering column needs to be removed so the fuel tank can be slid/turned. One of the three fasteners that secures the column support housing, the one that is the rotation stop, has a 5/16 nylock nut on the bottom, in addition to the "T" nut. Often, the bolt threads will gall in the "T" nut and then they strip out plastic that retains them and spin. When that happens, I just utilize an electric hand grinder to grind off the bolt head. I then flatten the plastic boss in the housing so I can utilize a flat washer and nylock nut in place of the "T" nut---but its a bit of a challenge getting it started and keeping a wrench on it. See this thread, post #18.

  8. #8
    martincom's Avatar
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    While you have the oil tank out, add an O-ring or two around the rubber body of the oil level sending unit followed by a gear clamp around the tank opening for it. They are notorious for leaking and some even pop out on their own.

    You may also want to go through your reverse mechanism, as you'll most things out of the way to remove it. See the thread I linked above and there are two threads in the "stickies" about it, as well.

  9. #9
    Moderator HiPeRcO's Avatar
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    The engine will often still run with zero fuel pressure, so I think it's much more likely that you have low voltage to the injectors. Either bad EMM or stator/flywheel problem.

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  11. #10
    martincom's Avatar
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    HiPeRcO makes a valid point, though I normally wouldn't expect multiple, unrelated, problems to occur simultaneously. None the less, it is easy enough to check. With a good, fully charged, battery; measure the DC voltage on the white/red wire that feeds power to the injectors. This must be done with everything connected. This power feed, white/red, wire also appears in the 4-pin diagnostic plug near the EMM. You'll need to back probe the connector with something small in diameter, such as an unwound paper clip. While cranking the engine, you should measure approximately 21 vdc, while running 45 vdc.

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