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  1. #1

    Need Help with 1996 SL 780

    Hi I am new to owning a PWC and new to this forum. First of all thanks for a great site !

    I have recently purchased a 1996 SL780 with the blue fuji motor. I have been reading several forums on here and conducting searches prior to posting this and am not able to rectify my problem. So I will try to explain what is occurring the best I can.

    The ski will fire up and run but not idle real well. Only the Mag cylinder is getting hot whether it's ran on the hose or in the water. It is extremely underpowered and will not rev up very much. It appears to be mainly be running on the MAG cylinder. There is no limp mode red flashing on the display but note the display is in poor condition with only partial numbers and lines being displayed. It does continue to show LOWPR for a small period of time then switch back to the selected mode then return to LOWPR on a continued cycle of this.

    I have taken advice from the suggestions offered on this site and have done the following.

    Compression test is at around 145 psi across all 3 Cylinders. ( the ski has had a complete short block and all cylinders etc replaced in 2005 and I have the bill from the marina the guy used to ensure this was done ).

    I went throurgh all the fuel lines to ensure no blockage and then pulled apart the fuel pump and cleaned it but did not appear dirty. I reassembled the pump and cranked the motor to ensure it was pumping fuel to all 3 carbs. It was but doesn't seem to be a very high pressure, but not sure if it should be.

    I dissasembled all the carbs completly cleaned them including the jets screens etc. They had all appeared to be extremely clean as well.

    I have charged the battery and the LOWPR does not go away and best that I can see on Volt mode it is showing 0.2v.

    I completely dissasembled the circut board and cleaned all contacts as a few appeared to have a small amount of corrosion starting then diectric greased all terminals and reconnected.

    I have tried running it with the gray wire from the CDI disconnected and then the Tan wire disconnected and both disconnected at the same time having no effect on the way it runs.

    I topped it up with fresh fuel thinking that being near empty could be the cause.

    I tried off the trailer and it will only rev up enough to lift the front of the ski a bit then just push along the water at a slow speed not reving up anymore.

    I have tried running with the PTO spark plug wire disconnected and it seems to run somewhat the same. I then put it back on and ran it without the CEN plug wire and it seemed somewhat the same. I tried rrunning with both the PTO and CEN disconnected and it wont run idicating to me that it must be using some power in one or both of the cylinders.

    I pulled all plugs and cycled the motor and all plugs appear to be sparking the same. ( note new plugs had just been installed ).

    Thanks for all your time and assistance on this as we are anxious to get on the water and have some fun out of this machine.


  2. #2
    BlueFishCrisis's Avatar
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    Welcome to the Hulk! What have you done to verify you have good spark at each cylinder?? In addition, if the MFD is acting up, try disconnecting the harness from it and see if anything changes...

    You can also try the MFD reset procedure, this has cleared up the loPWr for me on other units..


    MFD reset;
    You may need to first touch the Mode button to wake up the MFD
    Press and hold the MODE and SET buttons until CAL 0000 displays. The CAL display will usually show after 4 seconds
    Release both buttons?
    Press and hold the SET key
    While continuing to hold the SET key and within 2 seconds of pressing the SET key, press and hold the MODE key
    Don't release either key until the MFD shuts down (about ten seconds).
    After the MFD has shut itself down, press the mode key to turn the MFD on
    Depress the MODE key repeatedly until voltage is displayed and verify that the voltage reading has been restored.

  3. #3
    Great Info
    I did the MFD reset and it cured the LOWPR issue.
    It still runs the same though.
    Is there a way to know if it is in limp mode without the light blinking. The light blinks for a brief time on powering up the MFD but then turns off so the bulb is working.
    THANKS

  4. #4
    BlueFishCrisis's Avatar
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    Glad you got the MFD reset. If in limp mode the ski will not rev much over 4k rpm, in the water or out. The motor should run, poorly but run, on any 1 of the cylinders. The fact that you are able to remove the plug wires off of 2 with no change tells me that you have 2 dead cylinders. If compression is good on all as you stated, and you do in fact have spark on all three, (verifiy with a spark tester), than fuel can be the only variable. It is possible that you have damaged reed that are not keeping fuel in the bottom end. The other thing to check would be the carbs. Either way, sounds like the next step is to pull the carbs and intake manifold to check the reeds. Did you rebuild the carbs??

  5. #5
    I did not rebuild the carbs as they were done at a marina when the previous owner had it. They appeared perfect inside and not even a speck of anything in the jets or screens.
    I did some more tinkering today with the plug wires and to verify it will run it on the centre cylinder alone, the Mag cylinder alone but not so well on the PTO cylinder alone. I t does run better with them all as far as I can tell. Now with the MFD reset and actually being able to see the rpms, it will not rev past 4300. Idle shows it at about 2400 rpm ? Is that normal idle speed ? Is a spark tester different than a timing light ? How do I determine if reeds are ok are they something that just go on these or would that be a rare thing ?
    THANKS again

  6. #6
    BlueFishCrisis's Avatar
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    Please clarify, all the rpm readings you are indicating, is this in the water or out? If the ski will not go past 4300 rpm, then it definitely sounds like the rev limiter is kicking in. Verify that you have removed the gray wire from the CDI to the circuit board.

    Idle out of the water is usually around 3k +. In the water, you should idle around 1250 rpm.

    A spark tester is very different from a timing light. It is installed between the plug boot and the boot itself and will show the spark with an internal light. Something like this: http://www.jbtoolsales.com/lisle-206...-spark-tester/. I prefer the testers with an enclosed lighted indicator, vs the cheaper adjustable gap type.

    Reeds can break from old age, but are usually collateral damage from some other type of failure. If a previous owner had a damaged piston and replaced it, but didn't inspect the reeds, they could have been damaged as well.... Visual inspection is required to determine if they are OK>

    Sounds like it will run on each cylinder alone. I wouldn't expect it to idle well on just one, but it should run.

    Double check the gray wire connection in the ebox. If you are stuck at 4300, I would be looking at a limp mode rev limit issue.....

  7. #7
    To verify yes this is being on the hose out of the water so the rpms seem correct according to your info thanks.

    I conducted a spark check today and all is good. I then dribbled fuel in the carbs while it was running to attempt to try and prove that I had a carb or fuel issue. In doing this i learned that the PTO carb. appears to be blowing out the top and causing fuel and air to mist into the air. The more throttle the more blow by. Any thoughts on whey it would do this?
    I have not taken the carbs off for the fourth time "lol" to check the reeds yet.

    Thanks

  8. #8
    BlueFishCrisis's Avatar
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    Quote Originally Posted by droptop5.0l View Post
    To verify yes this is being on the hose out of the water so the rpms seem correct according to your info thanks.

    I conducted a spark check today and all is good. I then dribbled fuel in the carbs while it was running to attempt to try and prove that I had a carb or fuel issue. In doing this i learned that the PTO carb. appears to be blowing out the top and causing fuel and air to mist into the air. The more throttle the more blow by. Any thoughts on whey it would do this?
    I have not taken the carbs off for the fourth time "lol" to check the reeds yet.

    Thanks
    Check the reeds.

  9. #9
    Thanks again BLUEFISHCRISIS !!
    I took it apart this morning and sure enough one vain on the pto cylinder reed was totally gone as if it had been torn off. So good news is that the local dealer has these in stock and I picked up a new and reassembled it today. I then started it up and there is great improvement on how it runs. THANK YOU
    I have confirmed that it is stuck in limp mode with the gray wire attached, just bogs down and wont rev up, when I pull the grey wire off it will rev right up and is alot more responsive. The light is not on or flashing ? Please let me know what it could be or what my next steps are.

  10. #10
    Update. I was on the water with it this morning and seems to be a little hesitant most of the time. It will now pull out of the hole and actually plan and revs go to about 6100 rpm all with the grey wire off. Putting the wire back on immediately goes to limp mode. I left it on and pulled just the tan and same thing. I then tried with just the pink fuel sender wire pulled and same thing, i then tried with mfd fuse pulled and still limp. I pull grey wire and it revs up again.
    I did notice that the centre cylinder felt colder than the other 2 did. It will run on just the pto cylinder, just the mag cylinder but not with just the centre one. I took the time to pull each fuel hose from the carbs ensuring they were being fed fuel. I then confirmed each one was getting oil. I pulled the plugs and swapped them around and no difference.
    I ran it for a bit and seemed to have good moments and not so good moments.
    Please help as I want get on the lake and take it for a run but am afraid due ti its running condition.

    Thanks

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