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  1. #1
    bainer1290's Avatar
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    FUel System leak

    Well I'm starting to get the 99GP 1200 back together. I'm running a dual fuel supply similar to the one recommended by Novi here:

    http://greenhulk.net/forums/attachme...1&d=1201115199

    I don't have the carbs hooked up yet but I thought I would pressure test what I have assembeled so far to see if there are any leaks. I blocked the three lines that feed the carbs and the single return. The one way check valve is in place and is installed correctly to only allow air into the tank and not out. When I reached about 2 psi I could hear a bit of a leak and it got worse when I got to 5 psi. It seems to be leaking at the top of the stock fuel pickup where the metal fittings are located for the fuel supply, return and vent.

    Is this normal?


  2. #2
    maxadrenaline's Avatar
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    I have never heard of anyone pressure testing what you are doing.
    The diagram from Novi with the pressure guage shows fuel pressure from the carbs. The idea is to maintain an equal fuel pressure in all 3 carbs.

  3. #3
    most fuel tanks have a check valve to maintain a small psi to help fuel delivery ! Is this what your hearing? Z

  4. #4
    group K

    Pressure test fuel system - All pwc utilize a sealed fuel system that has a check valve on the gas tank vent. This check valve (which permits pressure in the gas tank but not out) causes pressure in the gas tank that helps deliver fuel to the carb(s). Any air leak in the fuel system that permits the leaking off of this pressure, will also affect fuel delivery to the carb(s) at low speeds. To test for leaks, follow this procedure. 1) remove the return line from the fitting on the carb. 2) Blow into the return line while sealing off the return fitting on the carb with your finger. This will pressurize the entire fuel system. In a quiet room you'll be able to hear any remaining leak in the fuel system. When you remove your finger from the fitting on the carb, fuel will eventually drip out indicating that the float chamber is primed full of fuel.

  5. #5
    bainer1290's Avatar
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    Thanks Z. I guess I am maybe going a bit overboard here. It is supposed to hold a bit of pressure but 5 psi is way too much. I'm just trying to make sure everything is in order with the fuel system so I don't toast the rear piston again

  6. #6
    Moderator OsideBill's Avatar
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    Rob I have never tested a fuel system for pressure, but I can tell you about a stupid mistake I made once. I pull the return line and the supply lines to drain my tank. I run the supply lines into my 5 gallon can and hit the return line with pressure from my air compressor makes quick work of draining the tank. I wasn't paying attention and just held the blow gun open and the tank, it over pressurized and blew the rubber seal around the fuel sending unit. Stupid on my part, short blasts of air is all it takes. Anyways the rubber seal is not available separately and only comes in an assembly with the fuel tank sending unit. Took me a while to find one through members here. Just be careful doing this.

  7. #7
    bainer1290's Avatar
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    That's a good idea to drain it, I have just used a hand pump in the past. I'll take a close look to make sure I didn't blow anything apart.

  8. #8
    Ramps's Avatar
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    Should you hear a little pressure coming out when you remove gas cap?

  9. #9
    Moderator OsideBill's Avatar
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    Quote Originally Posted by Ramps View Post
    Should you hear a little pressure coming out when you remove gas cap?
    Yes

  10. #10
    Ramps's Avatar
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    Then I do have a problem..I think it is at my fuel sending unit at one of the nipples probably the fuel return line. I noticed the nipple rotated very freely. What do you think????

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