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  1. #1

    Default "Hi Guys, I have an old YSE

    "Hi Guys,

    I have an old YSE 12 and the fuel pump doesnt seem to be working, it does not have the preassure to supply the fuel through the high preasure fuel line to the injector.

    it is an old pump, very simple construction with a piston like ram on a spring in the rear that gets pumped to supply the preasure to force fuel through a ball bearing and spring set up on the outlet side. when I take the high preasure hose off the outlet and crank the engine over there is no fuel coming out under preasure???

    Hope someone can help"

  2. #2
    Join Date
    May 2006
    pensacola, fl., u.s.a.

    Default "it is simple, but there are s

    "it is simple, but there are several things to check. is the cam in good order? are the rollers in the follower o.k? then there is the governer, and fuel limiter. I have seen some with wear to the cam/rollers enough to make impossible to time. is this a sudden thing, or has it deteriorated over time?"

  3. #3

    Default "Thanks Scott, I put my finge

    "Thanks Scott,
    I put my finger in where the cam is once i removed the pump and turned the engine over and could feel it pumping in and out, it has been 4 months since engine was last running, but it was running and starting perfectly.
    I did notice that there was some air bubbles forming around the govenor spindle which is sealed by an O ring.
    How much fuel should come out of the pump when turning it over by the starter motor, should it be a spurt under preassure, or as in my case it was just a droplet forming and dripping from the outlet when the high preasure hose to the injector was removed.

    thanks Scott"

  4. #4
    Join Date
    Dec 2005
    Vancouver , British Columbia , Canada

    Default "Hello Scott, I have found tha

    "Hello Scott, I have found that in almost all cases the plunger & barrel should be replaced. This unit does not pump vast quantities but slowly builds up te pressure to your injector. Make sure you are getting solid fuel to the pump from your fuel tank. Change the o-rings and mounting gaskets. If the regulator point is groved change that also, and for the price change the spring also. It is the size of a ball point pen spring. Good luck"

  5. #5

    Default "Thanks Guys for your help, I

    "Thanks Guys for your help,
    I have the engine running again,
    I had the govenor assembly replaced on the fuel pump -$125 for the part, they wanted $550 for all the parts to rebuild the tiny Pump so I thought I would try just replacing the govenor assembly first and go from there, as I had noticed a some fuel and air bubbles forming around the govener spindle, and it started pumping fuel again.

    I am also amazed at how little the govenor (throttle) spindle only turns from full speed to idle, like 1/8th of a turn!

    But all is good and running fine once again.

    Best regards,

  6. #6
    Michael Brown's Avatar
    Michael Brown Guest

    Default "I have been having trouble wi

    "I have been having trouble with my Yanmar YSE 12. The engine will run, then die out. It could run for 30-45 mins before it dies. I am changing fuel lines, fuel pump and replacing needle valve on the injector pump. I am looking for the pressure rating for the fuel pump to get a replacement- any ideas on the specs for this engine for fuel pump pressure? I am thinking it to be around 6-8 psi.

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