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  1. #1
    Squirtcha?'s Avatar
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    Pressurized gas tank

    Here's one for you. I have two 1996 ZXI 1100s. They're practicallty identical. One of the skis will build up pressure in the fuel tank. It'll actually blow the cap off the thing if you're not careful to release the pressure gradually. I mean blow it off like 30' away (first time and a big surprise). Learned to release pressure slowly and keep my face away.

    The other one doesn't do it at all.

    Doesn't seem to matter if they're partially full, empty or what.

    Which one is right? The one that doesn't pressurize, or the one that does? I'm assuming they shouldn't build pressure (at least not that much). It's gotta be like a 100 psi. Oh yeah, it built so much pressure that when the cap came flying off, it broke the little plastic loop that the chain connects to.

    Any idea as to what the problem might be with the incorrect choice?

    Obviously this is after they've been ridden and shook up a bit.


  2. #2
    Jmski333's Avatar
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    wow 30' thats impressive. there has to be a vent that is clogged somewhere. i'd assume on the cap or maybe there is a hose that vents the tank in the hull. i'm not really sure.

    Does the pressurized tank ski run differently? i know my boat would run like crap if i left the vent shut on the tank.

    correct me if im wrong but would it be a bad idea to drill a small hole in the gas cap? just like a 1/8 hole or something small. i'd give that a try. do it in the top of the cap so no gas would come out.

  3. #3
    Squirtcha?'s Avatar
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    Quote Originally Posted by Jmski333 View Post
    wow 30' thats impressive. there has to be a vent that is clogged somewhere. i'd assume on the cap or maybe there is a hose that vents the tank in the hull. i'm not really sure.

    Does the pressurized tank ski run differently? i know my boat would run like crap if i left the vent shut on the tank.

    correct me if im wrong but would it be a bad idea to drill a small hole in the gas cap? just like a 1/8 hole or something small. i'd give that a try. do it in the top of the cap so no gas would come out.
    Yeah, I'm not exaggerating. I work with compressed air and tools quite a bit and when I say 100 psi it's probably not far off.

    I'll try tracking down the vent thing. It makes sense.

    They don't seem to run any differently. Although I will say that the one that tends to pressurize has failed to start on me after running perfectly all day long. I attributed it to needing a primer, and have purchased them already. Just haven't installed them yet.

    Thanks for your input and I welcome anybody else's thoughts on this.

  4. #4
    DPeteLand PeteSkeet's Avatar
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    Quote Originally Posted by Squirtcha? View Post
    Yeah, I'm not exaggerating. I work with compressed air and tools quite a bit and when I say 100 psi it's probably not far off.

    I'll try tracking down the vent thing. It makes sense.

    They don't seem to run any differently. Although I will say that the one that tends to pressurize has failed to start on me after running perfectly all day long. I attributed it to needing a primer, and have purchased them already. Just haven't installed them yet.

    Thanks for your input and I welcome anybody else's thoughts on this.


    its gotta be the vent

  5. #5
    btldigger's Avatar
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    Guys keep in mind the "vent" lets air in the tank as the fuel level goes down so you dont create a vacume in the tank. The vent line has a check valve that lets air in but stops fuel vapor from comming out. I would say the one that actually has the problem is the one that doesnt pressurize.

  6. #6
    That's alot of pressure build up I find it difficult to believe that could be normal. I have a 97 1100zxi and I do not get any pressure in tank at all. My gas cans normally sit in the back of my truck in the sun and will bulge and build some pressure but not even close to what you are experiencing. The question is what could be causing it. The only thing I can think of right now is that the keihin carbs on your ski have a fuel pump built onto the front and rear carb that is pulsed by crankcase pressure, this may be a stretch but I wonder if it possible for one of the diaphrams to break and allow the pressure pulse into the fuel system? Maybe somebody else could chime in on wheter that could be possible.

  7. #7
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    That tank is just hours away from becoming a bomb

    Uh..that much pressure is going to pop a seam or blow a fuel line off a fitting and put lots of fuel into the hull. Fuel pressure test spec is 5 psi I believe.

    This would be the first thing on today's to-do list, not hard to diagnose, there is a vent line on the fuel pickup..trace it out seperate it at the t-fitting ( one valve is air in, other is air out) and do the old blow/suck test on it to see which valve is misbehaving. Kaw check valves are way overpriced btw, I'd use one from another ski brand that prices out cheaper.

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