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  1. #1

    another no start 96 slx 780

    hey guys i rebuilt my ski last year using the resources on this site took it on the water and it just stayed in limp mode (no mfd at the time, i got one this year).

    ski is a 96 slx 780
    this year i cleaned out the carbs, fuel pump, (both are freshly rebuilt last year using genuine parts maybe 3 easy hours on it) checked fuel in the fuel tank. (put some on the ground and lit a match, it caught fire immediately).. i'm pre mixed, oil port is blocked off.

    ski will crank, but no fire.
    the fuel checked out fine, i sprayed carb cleaner down the carb to give it a jump. not even a sputter. i removed the reeds and they all look like new. no cracks and clean. i removed the spark plug. cranked it with the plug out and can see the spark quite well. it's got great compression. battery is reading 10 volts while cranking. i even removed the water box to see if i could feel a pulse. the plugs get wet like they're getting fuel. mfd doesn't have any warning lights (like limp mode) i'm really at a loss from here.

    my only thoughts is that i could be getting too much fuel.. i tested pop-off pressure and was getting 24-28psi pop off. last year when i rebuilt the carbs i never tested it. this year when i tested it the needle was leaking so bad it wouldn't technically pop-off. i put the old needle back in and a spring that got me the 24-28psi, and here we are...

    i've gone through the polaris fuji page about a million times and i'm just at a loss.

    thanks.


  2. #2
    i would just think it would at least sputter a little bit. yesterday i left it sit for a little while. came back and it started immediately. i just wasnt prepared for it so i turned it off immediately. only to find that it wont start again. and continues to not start

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    another no start 96 slx 780

    10 volts while cranking is a weak battery.

    You have spark when the spark plug is removed but you may not have spark when all spark plugs are installed.

    If the engine is flooded with excess fuel it can drown the spark plugs. Wet plugs may not fire.

    My _guess_ is that a fresh battery and dry spark plugs will help. To light up a flooded engine hold the throttle wide open, no choke. This will maximize air flow through the engine while cranking. Crank for maybe 20 seconds, then let the starter cool for multiple minutes.

    Eventually the excess fuel should dilute in the air flow. If the engine fires let it run for 10-20 seconds. This will burn off the remaining excess fuel in the crankcase.

  4. #4
    Quote Originally Posted by K447 View Post
    10 volts while cranking is a weak battery.

    You have spark when the spark plug is removed but you may not have spark when all spark plugs are installed.

    If the engine is flooded with excess fuel it can drown the spark plugs. Wet plugs may not fire.

    My _guess_ is that a fresh battery and dry spark plugs will help. To light up a flooded engine hold the throttle wide open, no choke. This will maximize air flow through the engine while cranking. Crank for maybe 20 seconds, then let the starter cool for multiple minutes.

    Eventually the excess fuel should dilute in the air flow. If the engine fires let it run for 10-20 seconds. This will burn off the remaining excess fuel in the crankcase.
    oops,, forgot to mention the battery is less than a year old and was on the charger when it was tested. i also bought brand new plugs for it, to no avail.

    i pulled the carbs off tonight, to put in the old springs that were in them, and going to test again later this week. my guess is its flooding itself(the only plausible thing i can think of at this point) so i'm putting the carbs back to how they were before and go from there..

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by whitelightningz View Post
    Quote Originally Posted by K447 View Post
    10 volts while cranking is a weak battery.

    You have spark when the spark plug is removed but you may not have spark when all spark plugs are installed.

    If the engine is flooded with excess fuel it can drown the spark plugs. Wet plugs may not fire.

    My _guess_ is that a fresh battery and dry spark plugs will help. To light up a flooded engine hold the throttle wide open, no choke. This will maximize air flow through the engine while cranking. Crank for maybe 20 seconds, then let the starter cool for multiple minutes.

    Eventually the excess fuel should dilute in the air flow. If the engine fires let it run for 10-20 seconds. This will burn off the remaining excess fuel in the crankcase.
    oops,, forgot to mention the battery is less than a year old and was on the charger when it was tested. i also bought brand new plugs for it, to no avail.

    i pulled the carbs off tonight, to put in the old springs that were in them, and going to test again later this week. my guess is its flooding itself(the only plausible thing i can think of at this point) so i'm putting the carbs back to how they were before and go from there..
    10 volts while cranking is low. Battery if charged should be able to deliver 11.0 volts during cranking, with no help from a connected charger.

    If the battery cannot deliver strong voltage by itself while cranking then it is weak, or the starter motor is drawing an exceptional load.

    Sometimes batteries age rapidly and then die young.

  6. #6
    Polarisitis loonatik's Avatar
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    K, Correct me if I'm wrong, I thought 10.6 v rule only applies to red domestic engine!?

    whitelightningz, Try to crank it with only one plug out see if it runs. If it does you may have bad grounding somewhere.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow Where does the 10.6 volt minimum battery cranking voltage requirement come from?

    Quote Originally Posted by loonatik View Post
    ... Correct me if I'm wrong, I thought 10.6 volt rule only applies to red domestic engine...
    The Polaris red carburetor engines absolutely insist on strong voltage at the CDI or they will not spark, no fire, no start.

    The minimum threshold voltage at the CDI is right around 10.5 volts, depending on wiring configuration. I post 10.6 as the minimum voltage, but there can be losses in the wiring (and LR module) so even 10.6 at the battery during cranking may not be enough voltage at the CDI.

    A healthy and strong battery should be able to deliver substantially more than 10.6 volts during cranking, regardless of which color or model the engine is. To minimize confusion, I use more than 10.6 volts during cranking as the definition of a strong battery, regardless of engine model.

    The blue Fuji engines will indeed crank and spark with less battery voltage than required for the red engines, but that does not mean the battery is actually much good.

    I consider a battery that cannot hold the cranking voltage well above 10.6 volts to be weak. It may be weak from age, internal degradation, abuse, or just need recharging. If the cranking voltage still sags even after proper recharging, then that battery is internally weak and just not trustworthy, in my view.

    If the battery can still start the engine, why does it matter if it is not really strong?
    The most important job for the battery is not starting the engine on the trailer or at the dock. The battery is most critical when restarting the engine while way out on the water somewhere, away from land.

    Sometimes an engine no-start problem (fouled spark plugs or whatever) or unexpected bilge pumping heavily drains the battery before you can get the engine restarted. If the battery was just barely strong enough before, the extra cranking or bilge pumping can easily result in a battery that is now too weak to actually start the engine.

    Being stranded on the water carries real risks to the rider. If the weather turns or dusk arrives before you are found and rescued, there is real chance of bad outcomes. Wind and currents can carry the watercraft into a dangerous area or deeper waters.

    Reliable starting even under difficult conditions is a primary reason for replacing a marginal battery, even if it will still start the engine.
    Last edited by K447; 04-09-2015 at 08:01 AM.

  8. #8
    BlueFishCrisis's Avatar
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    I would get an inline spark tester and test each cylinder with that so compression is intact. I have lost cylinders before on the Fujis because of a pinched wire coil wire in the ebox.

  9. #9
    Polarisitis loonatik's Avatar
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    I see your point K447.
    Skis can't be push start in the water. One may try but I'm sure it's gonna be tough.

  10. #10
    Quote Originally Posted by K447 View Post
    Quote Originally Posted by loonatik View Post
    ... Correct me if I'm wrong, I thought 10.6 volt rule only applies to red domestic engine...
    The Polaris red carburetor engines absolutely insist on strong voltage at the CDI or they will not spark, no fire, no start.

    The minimum threshold voltage at the CDI is right around 10.5 volts, depending on wiring configuration. I post 10.6 as the minimum voltage, but there can be losses in the wiring (and LR module) so even 10.6 at the battery during cranking may not be enough voltage at the CDI.

    A healthy and strong battery should be able to deliver substantially more than 10.6 volts during cranking, regardless of which color or model the engine is. To minimize confusion, I use more than 10.6 volts during cranking as the definition of a strong battery, regardless of engine model.

    The blue Fuji engines will indeed crank and spark with less battery voltage than required for the red engines, but that does not mean the battery is actually much good.

    I consider a battery that cannot hold the cranking voltage well above 10.6 volts to be weak. It may be weak from age, internal degradation, abuse, or just need recharging. If the cranking voltage still sags even after proper recharging, then that battery is internally weak and just not trustworthy, in my view.

    If the battery can still start the engine, why does it matter if it is not really strong?
    The most important job for the battery is not starting the engine on the trailer or at the dock. The battery is most critical when restarting the engine while way out on the water somewhere, away from land.

    Sometimes an engine no-start problem (fouled spark plugs or whatever) or unexpected bilge pumping heavily drains the battery before you can get the engine restarted. If the battery was just barely strong enough before, the extra cranking or bilge pumping can easily result in a battery that is now too weak to actually start the engine.

    Being stranded on the water carries real risks to the rider. If the weather turns or dusk arrives before you are found and rescued, there is real chance of bad outcomes. Wind and currents can carry the watercraft into a dangerous area or deeper waters.

    Reliable starting even under difficult conditions is a primary reason for replacing a marginal battery, even if it will still start the engine.
    alright, compression is 120 across all three cylinders. spark tester shows i appear to be getting good spark. going to get a new battery next week anyway and see what happens. thanks for all the input guys.

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