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  1. #1

    VIDEO: Of the problem I'm having....

    Thought that I would post a video to see if anyone might be able to hear something that I might be missing.

    Many thanks to xlint89 & k447 for their troubleshooting help so far.

    The background:

    * 95' Polaris SLX 780 (bought non running)
    * New plugs & battery. (spark & voltage verified)
    * Good compression on all three cylinders
    * New Fuel Lines (clear path from tank to carbs verified, removed & cleaned tank)
    * Disassembled / inspected / cleaned Carbs. (reeds, needles, gaskets, screens, diaphragms all fine)
    * Disassembled / inspected / cleaned Fuel Pump (diaphragm fine & holds 5 psi vaccum).
    * Removed liquid (oil/gas) from impulse line (verified pulse)

    Engine will start with premix or starter fluid already in the Carbs..BUT will not pull it's own fuel.

    Hoped maybe someone heard something in the engine turning over or the brief time it runs that might tip you off to something.

    Any thoughts??





  2. #2
    bowsniper's Avatar
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    is there a restrictor anywhere in the system? in the carbs or in the return line? if you changed the lines and the restrictor is suppose to be in the return line and you dont have it in there, it wont build fuel pressure.

    if the restrictor is in one of the carbs, you may want to see if its in there or missing or plugged.

    the fuel restrictor builds fuel pressure.

    are you sure you didnt swap the wrong lines onto the tank putting them back on? or one on the other side by the fuel pump by accident?

    do you know exactly which nipple on the fuel tank is the reserve,main,vent? there easy to mix up or swap or cut the wrong line. I would go thru your diagram and check it again,,

    maybe start from scratch and pull it all out and do it again, this time using the whole system. its not necessary to install half the stuff to verify if its pumping gas, it just should work pluming the whole system., trust yourself.

    you may have a air leak somewhere in the cases. did you presuure check the cases? if you suck air, it wont pump fuel.

    maybe you still have liquid in the cases. its plugging the pulse line. if water or liquid gets into the diaphrams, the pump wont pump fuel.

    If you disconnect one of the fuel lines going to the carb and crank the engine, you should see gas coming from the pump out of the fuel line going to that carb. can you actually see gas coming from the pump line if you disconnect it? or nothing? if nothing, your pump isnt working.

    check th cap on the tank for cracks.

    at 65l'hr, you should see gas somewhere moving when it running.

    not the greatest idea using starting fluid to start it. Just get a little gas and 2-stroke oil mixed at 40;1 and use that instead. the starting fluid could cause a detonation and blow out your reeds in 1 bang. it doesnt usually have lubricant in that stuff either. it doesnt really burn it explodes.lol good way to bust a ring or piston.

    how long is your pulse line? it should be 12 inches or shorter.

    if you check everything again,, try using the gas to keep it running for a little while.. lets say 15 seconds actually running by you dribbling gas down the carbs so that maybe the whole system will prime its self and that may work..

    I know when I did mine, it took a little while to get it all the lines filled up along with the carburaters and the fuel pump and lines all filled with no bubbles. just 3 seconds on starting fluid wont prime it.

    fill your gas seperator with gas and 2-stroke oil too.

    Just a few things to consider. I dont have a 780 so hard for me to help ya.. but the basics are always the same.. fuel,spark,air

    you have air, you have spark right? is it bright blue? or a weak yellow on the plugs?

    then it must be fuel.. does the pump pump? how do you know? can ya see it moving? then wheres the issue, the carbs? why,,? keep digging, you'll find it.. it can only be so many things. then it has to work.

  3. #3
    Quote Originally Posted by bowsniper View Post
    is there a restrictor anywhere in the system? in the carbs or in the return line?
    restrictor is built into the fuel rail on the return line in the form of a barb with a pinhole in it.


    Quote Originally Posted by bowsniper View Post
    are you sure you didnt swap the wrong lines onto the tank putting them back on? or one on the other side by the fuel pump by accident?
    Verified....thought this at first as well. All is where it should be.

    Quote Originally Posted by bowsniper View Post
    you may have a air leak somewhere in the cases. did you presuure check the cases? if you suck air, it wont pump fuel.
    I was NOT able to create a vacuum on the impulse line (which I'm assuming goes into the crank case?). Should I have been able to old a vacuum in there?

    Quote Originally Posted by bowsniper View Post
    maybe you still have liquid in the cases. its plugging the pulse line. if water or liquid gets into the diaphrams, the pump wont pump fuel.
    I hooked up a shop vac fritted down to a barb and sucked it out. That thing could suck a golf ball through a rubber hose. I was able to get a little more fluid out of the impulse line with the shop vac as opposed to just cranking the engine into a jar (maybe a teaspoon). But short of disassembling the thing, I've got all the liquid out of there possible.

    Quote Originally Posted by bowsniper View Post
    If you disconnect one of the fuel lines going to the carb and crank the engine, you should see gas coming from the pump out of the fuel line going to that carb. can you actually see gas coming from the pump line if you disconnect it? or nothing? if nothing, your pump isnt working.
    I'll try this tonight. Good advice.


    Quote Originally Posted by bowsniper View Post
    not the greatest idea using starting fluid to start it. Just get a little gas and 2-stroke oil mixed at 40;1 and use that instead. the starting fluid could cause a detonation and blow out your reeds in 1 bang. it doesnt usually have lubricant in that stuff either. it doesnt really burn it explodes.lol good way to bust a ring or piston.
    NO MORE STARTING FLUID! Thankfully that was the only time I've been using starting fluid, I have been using premix in the past. Thanks!

    Quote Originally Posted by bowsniper View Post
    how long is your pulse line? it should be 12 inches or shorter.
    it's about 6 inches or 8 inches.


    Curious about the impulse line question. Should I be able to create a vacuum on the impulse line? My vacuum pump came with a bleeder kit and I was trying to use it to get any fluid out. Couldn't create a vacuum, so I switched to the jimmy rigged shop vac (that actually worked dam well).

    Any thoughts on should I be able to create a vacuum on the impulse line?

  4. #4

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    Had an identical issue. Mine turned out to be air in the lines coming from the tank, through the fuel selector to the fuel pump.

    your new lines, are they clear ones or black ones from the auto parts store. It is easier to see if the fuel is pumping on the clean lines, plus the bling factor. If you have any it might help to put a clear line between the fuel seperator & fuel pump.

    disconnect the line going into the fuel pump and see if you get fuel through when changing from on/res/off. At off you should be able to hold a vacuum. Others obviously you should get fuel through.

    also, how much fuel did you put back into the tank after you cleaned it out? When I redid my lines I messed up and didn't make my in tank lines long enough to get to the bottom of the tank.

    One other thing to check is the check valve for the vent line on the tank. Want to make sure it's there and working.

    Oh, go ahead and bypass the fuel seperator for troubleshooting purposes. once you have it running you can put it back in. bad seal there could be causing an air leak as well.

    Edit...just saw the video, didn't see that you had already bypassed the selector & seperator.

    Other thing I also did was to disconnect the pulse line at the cylinder, stuffed a towel down there to collect anything and cranked it over for a while. That got things cleared out. Also had to take the diaphram of the fuel pump off to clean it out. feel free to PM me, went through this exact thing last summer.

  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    When you disassembled the fuel pump, did the check valves look "curled up"?

    If the check valves aren't sealing, it will never push or pull the fuel.


    The valves have a natural curl to them. (from the roll they were cut off of). The curl needs to face DOWN in order to get a proper seal.

  6. #6
    Quote Originally Posted by xlint89 View Post
    When you disassembled the fuel pump, did the check valves look "curled up"?

    If the check valves aren't sealing, it will never push or pull the fuel.


    The valves have a natural curl to them. (from the roll they were cut off of). The curl needs to face DOWN in order to get a proper seal.
    I didn't see any check valves? There is the diaphragm that pulse the fuel side but there didn't appear to be any check valves on the outlets or inlet.

  7. #7

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    check valves are at the tank/hood area.

  8. #8
    bowsniper's Avatar
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    I'm not sure because i cant see your ski,, but does it have 2 lines in the tank or a fuel sender in it? if the 2 lines are there..

    they can curl up on ya if you bought the last of the roll at the store. i look for a full roll so theres no big bend in it. theres suppose to be weighted screens on the ends of them also to hold them down.. always measure the main tube and the reserve tube when replacing them, do them 1 at a time or else you'll forget which ones is which, then.....if your on the lake and you run dry, youll switch over to reserve and there wont be a reserve.

  9. #9
    blegan's Avatar
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    have you checked out fuel pressure coming off pump. & verify fuel inline restrictor.

  10. #10
    Never kick a terd on a Hot day! jorlando32's Avatar
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    The check valves xlint is refering to are 2 small clear discs on the center body of the fuel pump. There is one on each side and are held in by 2 black rubber nipples. Page 3.60 in the service manual.

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