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  1. #1
    retro's Avatar
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    03 MSX 140 runs for 1 hour then slowly craps out

    I'm working on one of my friends skis and have been trying to figure out this problem. It will run good for roughly an hour strait without stopping the ski then all of a sudden will crap out while holding wot. It will loose all power slowly, then either shut off or drop to idle. If I shut it off for a couple of seconds it will start right back up and run at wot normal for a minute then do the same thing. Sometimes it will run for 30 seconds, or 3 minutes and do the same. Hooked it up to DW and no faults what so ever. The only thing I can think is a coil might be weak, weak stator, or maybe a weird fuel regulater problem. If anyone has any input on this issue I appreciate any advice. This is what I have done and checked with no change in the way it runs.

    1. Checked fuel pressure on the return rail and holds steady at 20 psi
    2. Channged out tps with a brand new one
    3. Changed EMM with a known working one
    4. Changed intake air sensor with a new one
    5. Changed plugs with new ones
    6. Checked stater ohm/cranking voltages and all in spec.
    7. Checked for propper cooling from stater all the way to pump exit and has good flow
    8. Compression 120 across all 3
    9. Changed the Capacitor

    The fact that no fault codes are coming up are driving me


  2. #2
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    Fuel tank venting?

  3. #3
    retro's Avatar
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    That's a good thought. I have seen that happen on many carb models but never with an electric fuel pump. I will check the vent. I'm willing to try anything.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by retro View Post
    ... I'm willing to try anything.
    Exhaust temp sensor. If the sensor does not have the rubber bumper spacer (service bulletin update part, I think it is) the hard plastic exhaust pipe can rub on the wires and the sensor signal to the EMM gets crazy.

    Exhaust leaking into the hull? Does it behave differently if the seat is off?

    Jet pump or through-hull bearings binding up with extended running?

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by retro View Post
    ... Hooked it up to DW and no faults what so ever...

    The fact that no fault codes are coming up are driving me
    Digital Wrench depends upon the EMM having a clue as to what is actually going wrong. If the EMM's own diagnostics are not seeing the problem then DW is somewhat restricted in how much it can help.

  6. #6
    retro's Avatar
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    It runs the same with the seat off and no exhaust in the hull. I will check that temp sensor but I would figure that sensor only tells emm if it gets too hot and would trigger a signal to the emm to either go to limp mode, or if no signal would just trigger check engine. It's a weird one.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by retro View Post
    ... I will check that temp sensor but I would figure that sensor only tells emm if it gets too hot and would trigger a signal to the emm to either go to limp mode, or if no signal would just trigger check engine. It's a weird one.
    Unlike the carb engines the Ficht temp sensor is variable resistance so the EMM can read the actual temperature, not just overheat yes/no.

    ByranP bough an MSX 140 that was running weird. Turned out to be the temp sensor wires.

    I suspect the EMM cannot cope with a noisy or extremely variable signal from the temp sensors.

  8. #8
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    The exhaust temp sender should trip a check engine light though.

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by BryanP View Post
    The exhaust temp sender should trip a check engine light though.
    It should, but I am suspecting that certain temp sensor faults may not.

  10. #10
    retro's Avatar
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    I am going to go ahead and replace the exhaust temp sensor and check the wires while I'm there.

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