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  1. #1
    smitty564's Avatar
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    Need Help with 96' Polaris SLT 780 power loss problem ---Problem Solved!---

    My SLT 780 seems to be having what i think is fuel issues but not sure what is causing the problem. I will only get about 10 to 15 seconds of full power then the engine bogs down to 3000-3100 rpm, even when given full throttle it won't go past 3100 rpm and will maybe reach 15mph. (the low fuel light starts to blink at this time as well. but has a full tank.) then once it sits for around 15 minutes shut off, I will get another 10-15 seconds of full power then once again bogs to 3100rpm and slows to a crawl. No matter how long i wait idling around the water once the power cuts out after that first 10-15 seconds, it never comes back until its shut down and 15 minutes gos by.

    It idles fine and revs to 3000 rpm like normal.

    If i start it up and idle it around for a few minutes, the power will never cut in, But once it sits for 15 minutes, If i start if up and immediately give it full throttle, i will get that 10- 15 seconds of full normal power.

    It has had new fuel lines installed recently along with a new fuel filter.

    I have a video to show whats going on. If you pay attention to the sound the engine makes at the time of :55 to 1:00 and 1:06 to 1:11 you will hear the sound my pwc is making when the power is cut out. The link :


    If you have any ideas on what is going on i would appreciate the help, thanks.
    Last edited by smitty564; 08-28-2012 at 10:02 PM. Reason: Problem solved


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Check your elec stator (magneto) when it's warm. It may be failing when it gets hot.

  3. #3
    smitty564's Avatar
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    I will check the stator, but that still doesn't explain why I'm getting a low fuel light blinking. Could this problem be a failing fuel pump?

  4. #4
    BlueFishCrisis's Avatar
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    Quote Originally Posted by smitty564 View Post
    I will check the stator, but that still doesn't explain why I'm getting a low fuel light blinking. Could this problem be a failing fuel pump?
    Fuel pump has no alarm or ties to the electronics. Sounds like you are on the limiter due to a low fuel condition. You may have a bad fuel sender. If the float is bad it will sit at the bottom of the sender and not float like it should. I believe the MFD takes a few seconds to read low before it signals the low fuel alarm. The low fuel alarm and associated blinking red light will send your MFD into limp mode which should limit around 4k rpm...... Try removing the fuel sender leads from the ebox and testing them for proper resistance. What does your MFD read for fuel level?? You can also try removing the gray wire from the circuit board that connects to the CDI. This controls the limit function.

  5. #5
    smitty564's Avatar
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    The MFD reads 2 bars for fuel level when its blinking at me, and when i press "mode" or "set" it stops blinking and eventually reads 4 bars. Also the very top lines on the display don't work, but i can tell what the rpm is and what warnings come on. Before i unbolt and open the ebox, if i where to unplug the MFD right at the handle bars would this disable the limp mode that it is potentially stuck in?

    If i unplug the grey wire coming from the cdi will that effect anything else other than disabling limp mode?

    Is there more then one grey wire on the cdi?

  6. #6
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    The MFD is directly linked to the CDI and has no effect on limp mode. Each of the senders is linked to the LR54 which then grounds the grey wire from the CDI, triggering the limp mode. If the fuel gauge is lying and reading low fuel, it could be going into limp mode. Try disconnecting the grey wire from the CDI and see if the problem goes away. If that doesn't fix it I would suspect your stator is at fault.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by smitty564 View Post
    The MFD reads 2 bars for fuel level when its blinking at me, and when i press "set" it stops blinking and reads 4 bars.

    Also the very top lines on the display don't work, but i can tell what the rpm is and what warnings come on.

    Before i unbolt and open the ebox, if i were to unplug the MFD right at the handle bars would this disable the limp mode that it is potentially stuck in?
    Unplugging the MFD connector will prevent the Low Fuel condition from affecting the engine RPM, unless your model has a separate LR module function for RPM limit with Low Fuel.

    The stock 1996 SLT780 does utilize a separate LR-54 module to invoke Low Fuel RPM limiting. That means the Low Fuel RPM limit will happen even when the MFD is unplugged.

    The MFD display can be repaired. See my signature links under MFD for the details.

    The fuel level reading on the MFD is electronically dampened (averaged over time). If you are slowing down or stopping when you press the Set button to quell the fashing red LED then what may be happening is that at speed the fuel is sloshing around and creating a low fuel signal. When you stop the liquid fuel settles down and allows a higher reading.

    If your model has the old style fuel sender with a floating arm then this seems likely.

  8. #8
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    The slt 780 uses the aluminum tube sender

  9. #9
    smitty564's Avatar
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    I disconnected the battery before unplugging the grey wire leading to the cdi. When i connected the battery i noticed the MFD was still displaying low fuel and the red light started to blink again.

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by smitty564 View Post
    I disconnected the battery before unplugging the grey wire leading to the cdi. When i connected the battery i noticed the MFD was still displaying low fuel and the red light started to blink again.
    The gray wire does not affect the display.

    The gray wire simply tells the CDI to actually limit RPM. When you unplug that gray wire then the CDI will never limit RPM.

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