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  1. #1

    Stuck in Limp Mode? Already chk'd Polaris PWC knowledge & thread search

    Hi, longtime lurker, new poster. I have a '96 SLX780 purchased 4 years ago. Ran it for 2 years, has been stored the last 2. When I purchased it, the only thing that didn't work was the MFD. I tried the fixes but it had a circuitry problem on the circuit board. Ran fine, no issues, original oil injection system worked(s) but occasionally ran premix in it anyway (seemed to take a long time to go through the oil reservoir so I was always suspect, but never any issues). Last time out (2 yrs ago) was trying to get it on the trailer in heavy chop, and it went into limp mode. I knew it was low on fuel so figured that was the reason. Just recently brough it out of storage, went through all the de-winterization steps (winterized for long storage prior). Cranked right up w/ no issues other than being in limp mode (revs hard to about mid way or so and then just bogs). I have unplugged mfd, disconnected float sensor (although the float floats), disconnected oil level sensor, temp sensor, and gray wire from Heat/Fuel/Oil switch to CDI (both individually and altogether). Still revs hard to mid level & then bogs. All the jugs heat up, plugs are good, etc. Fuel & oil is old, but was having the same issue last time it was ran so seems like a continuance. Anyone have any ideas? Coil issue? CDI issue? Timing issue? Thanks! ~Dameron


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    What RPM is it "bogging at"?

    Are you out of the water when testing?

  3. #3
    I don't know the rpm, don't have a meter to test that. Its at the same revs (by ear) whether revved hard or feathered. If I keep the throttle on full, it will stay at the rpm its bogging like a limiter (with that flat "bogging" sound). Testing out of water.

  4. #4
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    The limiter will sound like its misfiring. It will not run smooth at all. Are you sure its the limiter? Unplug the grey wire from the the CDI and see if it runs normal.

  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    It doesn't take long to hit the rev limiter out of the water. And not having a tachometer means you don't know what it's revving to.

    Time to put it in the water. And get a Tach.

  6. #6
    Its not a case of "doesn't take long to hit the limiter." I ran the ski for 2 years before storing it, and it used to rev up to where you would think you could throw a rod. Just as it sounds like the power is coming on in the rev range, it flattens out and sounds like the timing is retarded or a plugged catalytic converter; "boggy." Taking it to water is not an option. To appease, I went and bought a multimeter w/ a built in tach function. I hooked my ski up to the hose so I had time to do everything properly. I could get the tach up to 1300rpm (x3 for 3cyl is 3900rpm). After that the reading is erratic, bouncing around mostly in the 100-300's ranges. There is a little tiny bit of revs left after the tach goes erratic, but the tach readout and the "bogginess" of the revs are about simultaneous. So, that readout is pretty close to the 4200 limp mode limiter.

    While I was running the ski on the hose, I kept feeling the cyl heads and the cooling rail to make sure it was not too hot to touch. #2 cyl (mag cylinder) did get so hot I could not touch it (by the end of the testing, ~5min). However, I did have the hose pressure at about half as recommended in the polaris pwc knowledge link somewhere, and the nose of the ski is inclined via a car jack under the trailer jack wheel to keep any rain that might happen from pooling in the footwells or collectining in the hull. I'd say its inclined 5-8 degrees. Might be related, might be an additional issue, or might be related to the inclined nose, either way, disconnecting the gray wire (which I stated I had done in the original post) should override the limp mode completely. I could touch the other two cyl and cooling rail. With the cylinder heating up, I couldn't setup the timing gun to check that, but I suppose I might be able to after the ski cools or sometime tomorrow.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    If you use a flush kit mounted to the water bar, it's normal for the FRONT or MAG cyl to get hot since the other 2 cyls steal most of the water supplied.

    If you are using the main water intake, and 1 cyl is hot, then there may be an issue.

    Have you done a compression reading?

    Have you pulled 1 spark plug wire at a time to see if the RPM changes? (looking for a dead cylinder)

    Do you have any of the carbs spitting excessive fuel when idleing? (possible broken reed)

    Have you tried cutting the plug wires back 1/4"?

    Was the ski properly winterized before storage?

    Have you gone thorugh the carbs since taking it out of storage?

  8. #8
    The ski was properly winterized before storage. And it was started and ran for 10-15 sec a couple different times after the 1st year of storage. I did not rev it enough at that time to discover the rpm limit issue.

    I did not use a flush kit, I used the main water intake hose.
    I intended to check for a dead cyl during the same diag time as the timing, so I haven't yet. I did check that all the wires are getting a pulse by hooking the inductor on the tach meter. Idle is a little rough, but not to where I would think it had a miss. It smooths out w/ minimal throttle.

    I haven't checked fuel flow in the carbs, just pulled plugs after running; all are wet w/ fuel and a little oil and consistent accross the 3. No compression check, I can't find my guage. Have not tried cutting the wires back, seem to be getting spark on all plugs. Since I can't find my compression guage, I figured it would rule out a compression problem if it will run on each cyl separately when checking for a dead cyl. If one of the cyl's is dead, then I would run a compression test accross them all for a baseline and diag of the "dead" cyl.

    The carbs have not been gone through since storage. I think they are a mess to work on and I don't have a space in the garage or a workbench to use. Since it is doing the same thing now as when it was last running in the water (trying to load it in heavy chop w/ low fuel, went from running strong to what I thought was limp mode), I have been trying to focus on issues that could have occurred at that time. When there isn't anything to check without tearing into something, I will tear into things at that time. I did check fuel and oil lines, check for leaks, lube cables, etc when I de-winterized it.

    Next things I plan to check:
    1.verify spark
    2.check for a dead cyl
    3.compression if there is a dead cyl
    4.How do I tell if a carb is spitting excessive fuel at idle? (more fuel on the plug or cyl compared to others?)
    5.Is it more likely for the crank to slip than shear the woodruf?

  9. #9
    BlueFishCrisis's Avatar
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    I think you will be chasing your tail trying to diagnose a malfunctioning ski when you haven't put it in the water and tried it with with fuel in the tank verifying that it actually is malfunctioning..............

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    So the ski was winterized, but then it was started a few times intermittentally? Was Stabil used in the fuel?

    Cut the wires back 1/4" It costs nothing, takes a couple minutes, and may give you a better spark and possibly fix a failing cyl.

    Do a compression test anyways, costs nothing and only takes a few minutes.

    Remove the FA and run the ski. if you see 1 carb spitting out more fuel than the other 2, chances are it's a broken reed.

    If you suspect a crank index issue, perform a crank index test. Costs nothing and takes a few minutes.

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