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  1. #1

    Join Date
    Jul 2015

    Polaris 2003 MSX 140 Engine Bogs down

    My Polaris 2003 MSX 140 Engine Bogs down after several minutes of good running 60+ MPH, then idles rough, let off throttle for a few seconds then reengaging throttle gets engine running smooth again but for a shorter period. Flush fuel and put in new fuel no success. What should I check now?

  2. #2
    CliffsidePM's Avatar
    Join Date
    May 2014
    Racine, WI

    A short history of the ski would help. How long you had it. etc. Did you check compression and fuel pressure, condition and type of battery? Do you have any codes on the display? Are you running in salt or fresh water?Update profile on where you are. There is a list of item to check when diagnosing these units. Take a look at K447 page for starters.


  3. #3

    Join Date
    Jul 2015
    The MSX 140 was just serviced prior to putting into the water. It has 55 hours, running in Lake Lanier fresh water. New battery and new plugs installed 4/2/15.
    I have had it five years service at start and end of every season. Did not run it for 19 months it was winterized and stored in a heated garage, had it prepped for season in April but only got in water 2 weeks ago and bogged down after 3 minute run. I have called 8 former Polaris dealers in Atlanta area no one works on these and no major help. Two ideas have been proposed: 1. fuel pump problem, this I question since once it runs it gets fuel so I believe its more in some control unit?
    2. Electronic Control Module has been identified by one former mechanic for Polaris but how to check this and where to get parts?

  4. #4
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    You gotta check fuel pressure. The fuel pressure regulator inside the fuel tank will fall off. When it does, no pressure... but will still run and seem almost normal... right up until it melts down a cylinder. Pressure should be ~20-22 psi at idle. Squeeze return line and it should rise to 30ish psi.

    The EMM brain for the Ficht system is also a known issue. Internal components are nearing end-of-life with their age and use. When the EMM starts going, it can lead to sporadic running/starting issues. Review all the info at the link Jajardas gave you. If you conclude a likely bad EMM... there are rebuilders out there that will repair your EMM (~$400-500).

    Also inspect the 2 check valve vents for the gas tank. A vac or pressure buildup could affect running. One valve is air-IN and is on the short Tee stub off the tank vent line hanging inside the hull. The other branch of the Tee leads to a hull mounted vent which is air-OUT. Ensure both check valves are free and working. Should be able to blow enough pressure one direction only.


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