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  1. #1

    Thumbs down Polaris msx 140 fuel pressure issues

    First off Iím new to green hulk and I recently purchased a 2003 Polaris msx 140 with 76 hrs. When I bought it it ran great(out of water of course) after a little investigation of registration it seemed like the the ski had been sitting for 4-5, and the smell and color of the gas agreed with that number. As soon as I put it in water it ran ok, I got into it hard and about 1 minute later it just sputtered and died. It would start right after but die shortly after planing off, so I brought it home and tested fuel pressure. And I think it was low(honestly I donít remember what it was since it was a year or two ago and I was not aware of the headaches associated with a Polaris pwc. So I went a replaced the fuel pump with a quantum one(upon research on other threads it seems like this specific pump doesnít draw too much current like other automotive ones. So this year I took it out with a new pump and it stilll did the same thing. So after being a little smarter and doing more research I found out the fuel pressure regulator was loose and about to fall out letting some pressure leak out but not all. So I fixed that with the 1/8 npt x 1/4hose barb fix and it now has good pressure AT IDLE(~25psi). So I took it for a test drive and it runs well till intermittently it starts slowly loosing rpm and sounds lean, so I installed a permanent fuel pressure regulator inline since I can tell this may be an on going problem, so under throttle the pressure drops anywhere between 5 and 15 psi. So I decided to gather some more info so I tested injector voltage at start itís 17-18v and 41v while running, which seems low but. When return line is piched off pressure goes to 40 psi at idle, but clamping doesnít help when actually driving the ski.(Side note it starts well but intermently stalls at idle but quickly starts right up too). On top of all that it also only runs out to 6200-6300 when running well and only 5700 when running poorly instead of the factory 6800. I also attempted to check the compression with a cheap gauge that had a kind sketchy adapter and all 3 cylinders came up with 92 psi which could explain decreased running rpm( at least when running well) but i plan on verifying that with a better gauge. So I think I narrowed it down to 3 issues, either the aftermarket fuel pump draws too many amps, the emm is bad, or the stator is bad. I plan on testing that, hopefully I can figure that out Iím sorry for the over complicated essay, I just got out of the school groove but I wanted to give you. Guys as much info as I know. Thanks to who ever has the stamina to read this and please guide me into the right direction if possible.


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Welcome.

    Do you have a way to monitor the DC voltage on the Brown wire from the fuel pump, while riding?

    It is supposed to stay very low the entire time the engine is running, maybe a volt or so (relative to engine ground). I suspect the Brown wire voltage from the EMM may be creeping higher, causing the fuel pressure to decrease.

  3. #3
    martincom's Avatar
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    Start with the simple test and check the current draw of the fuel pump. Your symptoms are near identical to those that I wrote of last year as a result of contaminated fuel. See this thread.

  4. #4
    Im not a wiz with electricity or a multimeter but I picked a similar set of these things at my local auto parts store. https://www.amazon.com/gp/aw/d/B07DM...?ie=UTF8&psc=1
    They’re rated at 30v, do you think they be able to test operational voltage? And as for current draw I should really figured out how how to test that with my meter too, I’ll do a research on that tonight. The only thing I know is that I cleaned the tank really well when I replacened the pump last season and installed new filters too so I don’t think that’s an issue.

  5. #5
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Reiffshark02 View Post
    Im not a wiz with electricity or a multimeter but I picked a similar set of these things at my local auto parts store. https://www.amazon.com/gp/aw/d/B07DM...?ie=UTF8&psc=1
    Theyíre rated at 30v, do you think they be able to test operational voltage?

    And as for current draw I should really figured out how how to test that with my meter too, Iíll do a research on that tonight. ...
    Try not to pierce the wire insulation unless absolutely necessary. Afterwards moisture can creep inside over time and corrode the wire internally. If you do pierce the wire, dab some liquid electrical tape over the tiny hole after you are done.

    Current measurements are tricky in that you have to find a place to insert the meter inline in the circuit.

    Be careful while your meter is configured for current measurements. If you touch the meter probes across a voltage source while the meter is in amps mode you can blow the fuse inside the meter. Or damage the meter, or the circuit.

  6. #6
    I will go out and figure out how to test that in the next few days here between work and the rain. Once I figure some numbers out I’ll post them up and bounce them off you guys. Thanks again

  7. #7
    martincom's Avatar
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    I was somewhat surprised by the amount of contaminants that made it past the filter on the bottom of the canister assembly. Carter (the source vendor for the canister) does not refer to it as a filter, but a strainer. Once I examined how loosely it fit on the bottom of the canister, my surprise was replaced by disappointment. It was hard to gauge how many contaminants were being held in the pleats and could wash loose again, seep past it, and clog the intake screen of the pump. So I replaced it. As you can see from my photos within the fuel contamination thread, it didn't take much at all to plug the pump inlet screen and it was very fine particles. The fact you had very old gasoline in it tends to also make believe that could be an issue.

    What works the best to measure fuel pump current draw is to disconnect the large 40 pin connector from the EMM. Pin 40, which has a brown wire terminating upon it, is the fuel pump enable line. You'll need some type of probe/contact that you can insert into the pin 40 receptacle without distorting or deforming it. Grounding pin 40 will cause the fuel pump to run (engine need not be running). To measure the fuel pump current configure your meter to measure current up to 10 amps. This, typically, utilize different jacks on the meter than the other functions. Connect the red (positive lead) of the meter to the pin 40 receptacle. Connect the black (negative lead) to engine ground point (bare metal part of engine). The fuel pump should run and the amount of current drawn displayed on the meter.

    I'm assuming you have a fuel pressure gauge. Monitor the fuel pressure while you have the fuel pump running by grounding pin 40. If is starts out at 25 psi and then falls off after it has been running for 15 - 30 minutes and the current draw remains fairly constant, that would tend to make me believe something is clogging the pump intake screen. Depending on the state of your battery, you may need to keep a charger on it while running these tests.

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  9. #8
    So, a little update, I tested current draw for 30 min and I got between 4.6 and 4.7A the whole time so I guess that eliminated a clog. Is that too much draw for the emm? In the meantime I switched the pressure regulator with another one I have, I’m just gonna test that and see though I doubt it will make a difference. I’m also having an extremely odd issue with my pump rn, the motor just revs up and I got little to no propulsion. I gotta pull it up on the trailer and check but it feels like when I suck up sea weed but I can’t feel anything in the intake grate like usual. The reverse gate is not stuck in nutral and I don’t see excessive impeller clearance, just another issue I have to deal with. Anyway I’ll het back in the regulator swap results once I fix that l.

  10. #9
    martincom's Avatar
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    When you made your current draw test, we you utilizing the inline regulator you spoke of in your opening post? If so, that will result in the pump drawing more current as the pump is somewhat "dead heading" when utilized with an inline regulator. Moreover, the inline regulator will cause a pump to fail quite abit sooner. We do not recommend the inline regulators---they are just problematic on the Polaris watercraft. I'm not comfortable with 4.6 - 4.7 amps of current draw. You are risking an EMM failure.

    I'd strongly recommend you return the in-tank OEM regulator. Once you have it back in place,measure both your current drain and the fuel pressure and report back.

  11. #10
    Oh, I’m sorry I didn’t specify that. It did use the oem regulator during the test, and I just swapped it with an oem one. I installed an aftermarket pump which is most likely the cause of the high current draw, I do have two oem carters in unknown condition laying around. Sounds like I’ll have to swap that in.

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