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  1. #1
    DrChuck's Avatar
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    2003 Polaris MSX140, excessive fuel consumption

    Hello
    Have a 2003 Polaris MSX140 with excessive fuel consumption. 170hrs on motor. Things I have tested. TPS test good, gas pressure is good, voltage to all 3 cylinder injectors is good. 20V. Motor does start but rough will get up to 30 but can't hit full throttle motor dies. Cylinder closest to the PTO (back of the ski) comes out wet. Have good spark in all 3 cylinders

    Any suggestions?
    Chuck

  2. #2
    Click avatar for tech links/info K447's Avatar
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    How are you measuring injector voltage on white/red wire?

    How did you decide the TPS is good?

    Compression check on all three cylinders?

    ĎExcessive fuel consumptionĎ just means one spark plug looks wet when you remove it?

    What is the history on this machine? Has it ever run properly for you?

  3. #3
    DrChuck's Avatar
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    1. How are you measuring injector voltage on white/red wire?
    I did a peak voltage measurement across the red/white & green( PTO cylinder) red/white & purple( middle cylinder) red/white & blue( stator cylinder) all came in at a solid 20V. Was surprised there was no fluctuation. Because it was exactly same I tested it on 2 different meters just to make sure and got the same results.

    2. Compression check on all three cylinders?
    no compression test

    3. ‘Excessive fuel consumption‘ just means one spark plug looks wet when you remove it?
    "excessive fuel" means take it out for 15-20 min and fuel tank drops 2 bars on the gas tank. Exhaust smells very rich too. Totally out of the normal consumption for the ski.
    Pulled all the spark plugs just to make sure. PTO cylinder was the only really wet one.

    4. What is the history on this machine? Has it ever run properly for you?
    I've owned it for 6 years. Bought it used did lots of work in the beginning but has been running great for the last 3 years. Has had the normal MSX 140 issues. Exhaust temp sensor, fuel pressure regulator, etc.

    BTW I would like to give you a shout out K447 your posts have helped me in the past. TY

    Chuck

  4. #4
    martincom's Avatar
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    Have you checked for spark on the cylinder with the wet plug?

  5. #5
    DrChuck's Avatar
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    Have good spark in all 3 cylinders

  6. #6
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by DrChuck View Post
    1. How are you measuring injector voltage on white/red wire?
    I did a peak voltage measurement across the red/white & green( PTO cylinder) red/white & purple( middle cylinder) red/white & blue( stator cylinder) all came in at a solid 20V...

    ...
    "excessive fuel" means take it out for 15-20 min and fuel tank drops 2 bars on the gas tank. Exhaust smells very rich too. Totally out of the normal consumption for the ski.
    Pulled all the spark plugs just to make sure. PTO cylinder was the only really wet one.

    4. What is the history on this machine? Has it ever run properly for you?
    I've owned it for 6 years. Bought it used did lots of work in the beginning but has been running great for the last 3 years. Has had the normal MSX 140 issues. Exhaust temp sensor, fuel pressure regulator, etc...
    That is not how Ficht injector voltage is checked.

    Ficht injector voltage is measured between engine ground and any white/red wire, with all fuel injectors plugged in. Which means sliding a thin wire probe or pin into the back side of a connector and connecting that to your meter red probe.

    With engine cranking the injector voltage should be over 20 volts. When the Ficht engine starts the voltage quickly jumps up to around 45 volts DC.

    That much fuel being consumed would suggest a fuel leak. Presumably the fuel is not leaking into the hull, although that should be checked later by riding with the seat off to confirm zero fuel is seeping out from a fuel hose connection somewhere.

    It seems that the Ficht injector on the PTO cylinder is gushing fuel into the cylinder. As a test, swap the center and PTO fuel injectors. Label them before swapping them. See if the wet spark plug problem moves or stays on the PTO cylinder.

    Report back.


  7. #7
    DrChuck's Avatar
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    OK I retested the injectors as you said to and exactly as you said. Starts at 20V and jumps right to 45V once started.

    No fuel leak in the hull. Checked by driving around with no seat. (Very loud BTW)

    I have never taken an injector off. Will try that next. Can you rebuild them? Is that something that can be done by a very mechanically inclined person?

    Chuck

  8. #8
    DrChuck's Avatar
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    Removed the PTO and middle injector. PTO looked pretty clean. Middle was a bit dirty. Thoughts?

    Has anyone replaced the o-ring above the injector as part of maintenance? Looks like they use the o-ring in compression to keep the injector tight on the engine. Thought was in time and so many compression cycles the rubber o-ring would be worn out. IDK maybe I'm way off base but just a question.

    Done for the night
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  9. #9
    Click avatar for tech links/info K447's Avatar
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    That fat thick o-ring on top of the injector is an anti-vibration thing. It does not clamp the injector to the cylinder head.

    The two bolts and the clamp ring at the base of the injector hold it tight into the cylinder head injector bore.

    Do not over torque those two bolts and make sure the injector is aligned with the bore.

  10. #10
    Msxslayer's Avatar
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    Change the o rings in side the injector it self, it screws apart. Fairly simple ,
    If the pto injector is cleaner in the tip. Makes me think itís leaking

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