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  1. #1

    fuel pump question

    I hooked up my mikuni triple pump today and was wondering if it matter which way it's mounted? As it is now I have all three fuel outlets pointing down. I ask because I have to prime it so much before it'll take fuel and start up. Possible because the house I have coming from the separator has a couple inches where fuel has to flow up into the inlet of the pump? Is the gravity feed that important on these things?


  2. #2
    Pump needs to be in the lowest part of the hull and the pulse line needs to be short

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    If you have to do a lot of cranking that suggests there maybe an air leak into the fuel lines somewhere between tank and fuel pump inlet. The fuel lines should hold fuel once the air gets pulled through. If the fuel drains away then that means there is air getting into the hose somewhere.

    The fuel pump is best mounted low in the hull, but not so low that it is below the pulse nipple on the crank case. You want any liquid that happens to get into the pulse hose to easily drain back into the engine.

  4. #4
    oh really? even shorter than the factory pulse house? because I just mounted it right where the factory pump was and used the original pulse house...and it won't pull fuel. Does that sound right to you guys? I mean it HAS to be mounted lower with a shorter pulse house for it to work? Also should the main fuel house from the seperator be as short as possible?

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow Requirements for the Mikuni Triple outlet fuel pump to work properly on a Fuji engine

    Quote Originally Posted by lockaby32 View Post
    ... I just mounted it right where the factory pump was and used the original pulse house...and it won't pull fuel...
    Even in the stock location it should work well enough. Something is wrong.

    To pump fuel you need;
    Good compression in the PTO cylinder, and working PTO intake reeds
    Decent pulse hose connection to the fuel pump (not soft or leaky at the nipples)
    Pulse hose must not have liquid inside, and must be positioned so it will drain into the engine
    Working fuel pump with a non damaged membrane and good condition internal valves
    Correct connections to fuel pump nipples for pulse hose and supply hose from fuel tank
    Every fuel hose connection between fuel pump and fuel tank must not leak air
    Every device between fuel pump and tank must not leak air (filter, selector valve, water separator, etc)
    The fuel pickup at the tank must be connected to the correct nipple
    For early Polaris fuel pickups (650 & 750 engines) which have actual fuel hose inside the fuel tank, that hose must not be degraded or damaged

    Actually, this list applies to all the Fuji and domestic carburetor engines, even those with the fuel pump built into the carburetor.

  6. #6
    Cool thanks for the help. I shall try lowering the fuel pump tomorrow. I'm also going to try running a hose straight from the tank to the pump to narrow down a possible air leak. Put it in the water earlier and it would start...but would die once giving it throttle. One question....is it normal for the fuel in the separator be full and then drop to about half once giving it throttle? It seems to die every time the fuel in the separator drops to half and I was told that's a sign of an air leak?

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by lockaby32 View Post
    ....is it normal for the fuel in the separator be full and then drop to about half once giving it throttle?

    It seems to die every time the fuel in the separator drops to half and I was told that's a sign of an air leak?
    The only way for fuel level in the separator to drop is if there is air leaking in.

    Check the separator seal.

  8. #8
    Checked the seal it's in good shape. So the fuel level should always stay full in the separator when running? Is it dropping halfway a good sign of why it's dying? You thinks it's more than likely an airleak, or maybe I just need to drop the full pump down and shorten the pulse house. I'm going to try hooking the fuel tank straight to the pump to see if it'll run right that way.

  9. #9
    Ok so turns out its only running on 1 cylinder. Shortened the pulse line and ran one hose directly from the tank to the fuel pump. The 1 cylinder that's running is the only nipple on the pump that actually shoots out fuel "more like spurts out". The other 2 do nothing. Could my new fuel pump be bad or is it more than likely something else?

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Verify that you have the fuel hoses connected to the correct nipples. See this post;
    http://www.greenhulk.net/forums/show...=1#post1101333

    Is your triple outlet fuel pump round or five sided (pentagon)?


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