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  1. #11

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    Just to chime in with my 2 cents...

    I donít think the issue is with the reeds. If it were, gas wouldnít be leaving the fuel /water separator to be replaced by air, unless there is an air leak between the separator and the fuel pickup.

    Another very unlikely possibility is what K447 suggested and the hoses at the tank fitting are swapped Ė your fuel separator is pulling air from the tank fuel return and then when it sits overnight the tank pressure pushes fuel back through the fuel return line since it may be connected to the fuel pickup. It would also be a slow process due to the restrictor between the tank and the carbs, and the check valves in the fuel pump. Just a possibility.


  2. #12
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by SeaBee63 View Post
    Just to chime in with my 2 cents...

    I don’t think the issue is with the reeds. If it were, gas wouldn’t be leaving the fuel /water separator to be replaced by air, unless there is an air leak between the separator and the fuel pickup.

    Another very unlikely possibility is what K447 suggested and the hoses at the tank fitting are swapped – your fuel separator is pulling air from the tank fuel return and then when it sits overnight the tank pressure pushes fuel back through the fuel return line since it may be connected to the fuel pickup. It would also be a slow process due to the restrictor between the tank and the carbs, and the check valves in the fuel pump. Just a possibility.
    I doubt it's the reeds also. But, with them suggesting the reeds were "iffy" on the PTO, and that cylinder operating the fuel pump, I think that needs to be removed from the list of possibilities before moving forward.

  3. #13

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    Polaris SLT 780 idle issue & water separator

    Yes but weíve already concluded earlier in the thread that itís getting 130 psi compression on all three cylinders, and his fuel pump seems fine because itís removing fuel from the separator. The symptom is the air thatís being pulled into the separator after that fuel is pulled out while running the engine. It has to be coming from somewhere because in a correctly configured and working fuel system the only possible point of entry of air would be the fuel pickup at the bottom of an empty fuel tank.

    After confirming that the hoses are connected properly at the tank, I would disconnect the fuel system between the pump inlet and the main outlet at the tank fitting, drain it of fuel, plug one end with a bolt or something, and put 10-15 psi of air pressure on it to see if thereís an air leak. To make a leak easier to spot you may want to spray the hoses and fittings with some water with a bit of dish soap in it and look for bubbles. If that proves to be fine remove your fuel sending unit and thoroughly check it Ė maybe thereís a crack high up in the internal pickup tube.

    This would also be WAY easier to check first before switching out reeds.

  4. #14

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    Quote Originally Posted by SeaBee63 View Post
    Yes but we’ve already concluded earlier in the thread that it’s getting 130 psi compression on all three cylinders...
    Wait, just thought about this a bit more and compression IS NOT an indicator of good or bad reeds, so ignore that part of the comment. I do still believe the reeds are working well enough for the fuel pump to remove the fuel from the separator and to pull in air.

  5. #15
    Alright so this morning I swapped the reeds and put the best looking one at the PTO cylinder. Removed the check valves and inspected. Both seem to be workings properly. Even put another Oring on the separator to be safe. Fired it up and the separator filled up perfect. Hereís where Iím at now....

    Took it to the water today, put it in and the thing started and idled really good! Awesome start. But after about a minute or two of bombing around it started to idle very badly again. Looked and the separator was back down quite low! Limped it back to the dock and onto the trailer. So Iím really stuck right now? Cannot figure this one out. Thing ran like a rocket ship when it was running good but by the end, had almost NO power (didnít wanna push it for to long) so brought it right back.

    Pulled the fuel cap and tank had pressure! Ran without cap, no change maybe will pull the fuel pump and ensure the diaphragms are in perfect condition? What would you guys think the next step should be?

  6. #16
    Seabee sorry i didnt see your post before posting my last! Tmrw i will remove hose from fuel pump inlet and main line of tank outlet. Plug one end, and youre saying to pressurize that and see if theres an air leak. Am i understaning that correct?

    Let me ask you guys this.. So I replaced the o-ring on the separator with a standard Buena O-ring (typical plumbing oring). I replaced it twice as indicated in my last posting but when I removed the one I had put on ( the first time I replaced) it seemed as if the fuel had almost enlarged the oring? Im not too familiar with rubber compounds but should I be using something such as a Viton or Nitrile oring? Meaning is a standard Buena oring not designed to be used around fuel and could that be causing the issue? Because each time ive replaced that oring I had thought id solved that problem but it was only temporary?

  7. #17
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Buna N and Viton seem to be what showed up in my search for fuel related O ring material.

    Not sure why you were fine, then lost fuel level in the separator again. Easy test would be to install a new O ring again and see if it is fine. (nothing else done)

    If it works, that is the issue. And if it fails again later, might need a different material O ring.

    Note: re-using reeds is usually not suggested. But if you do end up doing it (I know you already have for testing purposes) it is important to make sure they are installed in the same direction. Some materials if flipped over may crack.

    The reason I mention this is it's quite possible the reeds you replaced, might have let go also. Just something to keep in the back of your mind. ( a general test for this is to remove the flame arrestor and run the engine on the garden hose. If that carb is spitting a lot more fuel out the top VS. the other 2, that is a good sign the reeds have failed.)

    If it's not either of those 2 easy to check tests. Start from the beginning.

    Pressure test the fuel tank. Make sure there is no crack in the tank or leak at the fuel pick up gasket.

    Make sure the vents are installed in proper directions. 1 will allow air into the fuel tank, not out. The other will allow air out of the fuel tank, but only after 2 psi is applied to it.

    Fuel pick up tube would need to be removed for testing of it. visual inspection for cracks, and pressure or vacuum testing of the pick up circuit.

    Pressure or vacuum test of fuel hoses up to the water separator. This would also test the fuel selector valve as well. (if yours is original, it might be a good chance this might be leaking air)

    Make sure hoses are installed correctly on the water separator.

    You can test the fuel pump by installing a vacuum pump on the pulse fitting side of the fuel pump. Apply about 3-4" of vacuum to the fitting and it should hold indefinitely. If it drops, you have a leak in the fuel pump.

    Make sure your pulse hose is short (suggested to be under 12" in length) Has a good connection on both ends, and is NOT filled with any type of fluid.

    Check the pulse fitting on the engine case. I have found one to be loose since it's just a press fit.

    Hopefully this helps

  8. #18
    Awesome information thank you! So this morning before I changed the o-ring in the separator, I did what was suggested and I removed the inlet hose from the fuel pump, and the outlet at the tank. I then pressurized it to about 8psi and sprayed the entire separator aswell as the fuel selector (I bought a new one when I replaced the fuel lines) with soapy water. No air leaks anywhere. No bubbles and psi held at 8. This I assume rules out the separator & selector for being the cause?

    I did pull the arrestor and did not have any fuel being spit up out any of the carbs! I would definitely like to pressurize the fuel tank and also ensure the sending unit gasket is good. Is there a good write up somewhere on doing this because I’m not quite sure how to test that.

    Also will pick up a vacuum pump as you described and test the fuel pump! It’s got all new gaskets but don’t wanna leave anything out at this point! So today I will try and get those two tests complete and see where we’re at! Also will inspect pulse line and connection as mention.

    Stupid question..Is it at all possible that something is wonky in the carbs and it’s just dumping way to much fuel into the cylinders for the pump to keep up? The plugs are always very wet and even the tops of the cylinders are aswell? Is this normal to see when running at idle / on hose? From what I understand doin a plug chop is the only way they will come out dry?

  9. #19
    Click avatar for tech links/info K447's Avatar
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    Reminder that the fuel system from fuel tank to fuel pump INLET is under mild suction, not pressure, as the fuel pump works to draw fuel from the unpressurized fuel tank. So the fuel/water separator must remain sealed when slight vacuum is applied. But you cannot use soapy water to hunt for leaks when using vacuum.

    So to is Ďeasierí to pressure test the system using air pressure, but the results may be misleading.

    Did you confirm that the correct inlet and outlet fittings on the separator are going to the tank and towards the fuel pump?

  10. #20
    Did confirm the lines are correct! Arrow into separator comes from tank and arrow out of separator goes to fuel selector. I pulled vacuum on the fuel pump and set at 4”. Held it there for about 10 minutes and it did loose maybeee .5”? Is that a concern?

    K447, can I preform the same test of unhooking the line at fuel pump and tank but hook the vacuum pump instead. Would that be a better test?

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