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  1. #1

    MSX 150 False Boost Reading???

    Guys,

    I need some help here. After reading posts on this forum from other MSX 150 owners I realized that mine was not running at its full potential. I'm currently peaking at about 6800 RPM @ 55-58mph. So I called the Polaris dealership I bought it from and they had me bring it over. They hooked it up to digital wrench and all of the diagnostic tests passed. I noticed that while digital wrench was receiving real-time readings from the sensors while the engine was shut-off that that boost pressure and manifold pressure were at 14.8 PSI. Now mind you the engine is shut-off. So we pulled the boost sensor only to find oil on it. We carefully cleaned it and tried again only to yeild the same result. The dealer went looking for another sensor and ended up using one off of a brand-new 2006 Polaris Snow-mobile that used the same sensor. After hooking up this sensor the reading jumped to 19.8 PSI..again while the engine is not running. Correct me if I'm wrong but shouldn't the manifold and boost pressure be at 0 PSI while the engine is not running? We're still scratching our heads and he is in the process of contacting Polaris. When out on the water my MSX runs ultra smooth, it just never reaches top speed. I currently have 36 hours on it and all necessary maintenance has been done (valve lash check, etc...). The service manual indicates that max nominal boost pressure is 16 PSI and 18 PSI is overboost. If that is the case I guess I wasn't creating much better than 1.2 PSI of boost since the computer right off the bat thinks it's currently running at 14.8 PSI. Any help here would be greatly appreciated.

    Thanks,

    Ryan


  2. #2
    Moderator beerdart's Avatar
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    Ryan
    Glad you made it and welcome to the Hulk!!!

  3. #3
    Thanks for the info to come over here. I hope I can find some answers!!

    Ryan

  4. #4
    Moderator beerdart's Avatar
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    I am not a MSX guru but my gut tell's me that you have a bad ground/Wire some where. Check the resistance of the sensor wire to the brainbox.

  5. #5

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    It is reading atmospheric pressure so it would be right at 14 psi
    there is a bulletin out that you can but boost gauge in would show over atmospheric pressure
    Later cd
    Last edited by chip; 09-21-2006 at 06:48 PM.

  6. #6
    2&4strokepolaristech's Avatar
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    msx problems

    ok is your intake tract clean of oil? is the intercooler clean as well? what is your oil level? when did all this start. i need more information? your are turning 6800 rpm? it could be a few things but before i starting getting into it i need more information? also just so that you know that so called "boost gauge" is directly hooked to you tach and does not read boost just a bar graph of rpm it is a gimmick for the customer. if you were to plug that mfd into a msx 140 it would read boost as well b/c it works off the tach signal in the mfd.to install a boost gauge just get a 1/8" vaccum tee and some hose and a boost gauge. install it in two places. first is at the wastegate solenoid. in the line coming from compressor housing. this will give you boost at housing. then install it on the intake manifold side inline with the hose that is on the intake manifold/fuel pressure regulator. this will give you boost at the manifold. if there is a big diffrence in the two you have a leak in the system(charge tubes/intake manifold/etb adapter/intercooler) also you will not get a reading of boost unless your are under a load(in the water) please let us know more information on what happened(did you roll it or overfill it with oil or injest water)
    Last edited by 2&4strokepolaristech; 09-23-2006 at 10:39 PM.

  7. #7
    Connecticut CrazyA's Avatar
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    Quote Originally Posted by 4strokepolaristech
    also just so that you know that so called "boost gauge" is directly hooked to you tach and does not read boost just a bar graph of rpm it is a gimmick for the customer. if you were to plug that mfd into a msx 140 it would read boost as well b/c it works off the tach signal in the mfd.
    The cat's out of the bag... just like our bigbore Matrix, right Jay? Yup, it's got a "boost" ga. on it. Called Jay a few weeks back and he informed us that we had a 150 MFD. Funny $hit right there...

  8. #8

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    hmmm , im no expert , that why i hate tha idea of forced induction on jet ski's just makes it that much more complicated , any way if guys got tha need for speed an got tha cash supply an demand will be in affect ,,,,

    anyways sounds like you have major engine damage 2 have oil in tha manifold unless its a 2 cycle then you have a rich of mixture of oil an gas fowling tha sensor , or there is some fualts in tha wireing harness these machines arnt suspose 2 be at 18 psi are they ? if tha sensor works a blow off valve i would inspect that ,

    geezzz , i ride tha oldschool's im glad it doesnt have a t/c or s/c just another thing 2 break ,

  9. #9
    I still need to check the entire tract for oil. After removing the boost sensor we found oil all over it. We cleaned it and I tried running it again. I can get to about 7000 - 7100 now. The dealer indicated to me that that the prior owner had overfilled it on the first due oil change. The dealer then re-did the oil change for him properly but did not clean the intake tract. The oil is now at the correct level. I believe the next step is to check the intake and intercooler and be sure its totally clean of any oil. To answer your question of when this started...well I've been riding it all summer since I purchased it not realizing that is wasn't running at its fullest potential. Apparently the prior owner never noticed since he wasn't much of a power rider...just lisure riding. Its never been rolled on my watch and the prior owner said that he never rolled it. Any ideas why I can't hit the 7800+ RPM mark?

    Ryan

    Quote Originally Posted by 4strokepolaristech
    ok is your intake tract clean of oil? is the intercooler clean as well? what is your oil level? when did all this start. i need more information? your are turning 6800 rpm? it could be a few things but before i starting getting into it i need more information? also just so that you know that so called "boost gauge" is directly hooked to you tach and does not read boost just a bar graph of rpm it is a gimmick for the customer. if you were to plug that mfd into a msx 140 it would read boost as well b/c it works off the tach signal in the mfd.to install a boost gauge just get a 1/8" vaccum tee and some hose and a boost gauge. install it in two places. first is at the wastegate solenoid. in the line coming from compressor housing. this will give you boost at housing. then install it on the intake manifold side inline with the hose that is on the intake manifold/fuel pressure regulator. this will give you boost at the manifold. if there is a big diffrence in the two you have a leak in the system(charge tubes/intake manifold/etb adapter/intercooler) also you will not get a reading of boost unless your are under a load(in the water) please let us know more information on what happened(did you roll it or overfill it with oil or injest water)

  10. #10
    I don't believe its engine damage since the PWC still has no problem getting up and going and is ultra smooth with no smoking. I think in this case when the oil gets overfilled it passed out of breather tube into the intake manifold thus causing oil in the system.

    Ryan

    Quote Originally Posted by 97sltx1050
    hmmm , im no expert , that why i hate tha idea of forced induction on jet ski's just makes it that much more complicated , any way if guys got tha need for speed an got tha cash supply an demand will be in affect ,,,,

    anyways sounds like you have major engine damage 2 have oil in tha manifold unless its a 2 cycle then you have a rich of mixture of oil an gas fowling tha sensor , or there is some fualts in tha wireing harness these machines arnt suspose 2 be at 18 psi are they ? if tha sensor works a blow off valve i would inspect that ,

    geezzz , i ride tha oldschool's im glad it doesnt have a t/c or s/c just another thing 2 break ,

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