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  1. #1

    Need help !! 1996 sl 780

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

    Not sure what section this should be posted in.

    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 tried running it with the MFD unplugged with no change in the way it runs.

    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 running with both the PTO and CEN disconnected and it wont run indicating 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 much for the 780? stimpsonjcat's Avatar
    Join Date
    Apr 2012
    Georgia - Lake Lanier - near 6TH
    Are CEN and PTO all wet? They ought to be if the spark there is bad. If dry and you see good spark there then I'd suspect the carbs.

    If you dump some premix in each carb does it run better until that gas is used up? Try it per cylinder too.

  3. #3
    Join Date
    Jul 2007
    Cedar Rapids,Iowa
    Check this link out and watch the video halfway down.
    Last edited by K447; 05-23-2013 at 11:37 PM.

  4. #4
    la90043's Avatar
    Join Date
    Oct 2006
    Los Angeles
    Yup. run it on the water. take off the the flame arrestor and i like to use a spray bottle with fuel/premix in it and spray into each carb. if it gains speed and reacts to that. then for sure its fuel delivery. dont tip the boats though with the seat off doing this.
    Quote Originally Posted by stimpsonjcat View Post
    Are CEN and PTO all wet? They ought to be if the spark there is bad. If dry and you see good spark there then I'd suspect the carbs.

    If you dump some premix in each carb does it run better until that gas is used up? Try it per cylinder too.

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