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Results 1 to 15 of 15
  1. #1

    Default Fuel pump question

    Should the fuel line from the fuel pump to carb hold pressure after you turn off the ignition.

    Been having with engine bogging down after about 1/3 throttle under a load so I hooked up a pressure tester on the fuel line that goes from the pump to the carbs.

    Could only get about two pounds of pressure at idle and hardly any at 1/2 throttle with no load on engine., kill engine and no pressure.

    The pump has new gaskets and diaphragm.

    Could it be bad check valve in the pump.

    Thanks
    Milton

  2. #2
    Join Date
    Sep 2010
    Posts
    19,802

    Default Re: Fuel pump question

    There is absolutely no reason for pressure in there when motor is not running !!-----Do some more trouble shooting on other systems.-----Or perhaps open low speed mixture needles on carburetors 1/8th turn at a time and see if bogging goes away.---Yes it could be that simple !

  3. #3

    Default Re: Fuel pump question

    Should it have pressure when ruining at half throttle.

    Milton

  4. #4

    Default Re: Fuel pump question

    How do I pressure test the fuel pump. ??

    Milton

  5. #5
    Join Date
    Sep 2010
    Posts
    19,802

    Default Re: Fuel pump question

    Run the motor.------Then have an assistant operate the manual pump.-----If motor keeps running the fuel pump on the motor is defective.----These pumps are elegantly simple ( my opinion ) and it should be easy to figure out what is wrong.-----The pumps operate with pressure pulses from the crankcase so need to look into that too.----Could be issues with crankcase sealing !

  6. #6
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,836

    Default Re: Fuel pump question

    You should see at least 5 psi at the carbs at all time.

    Jeff

  7. #7

    Default Re: Fuel pump question

    The most I can get is 3 psi

    New pump rebuild

    Each cylinder has 125-130 psi

    New fuel lines

    New fuel filter

    Have good positive and negative pressure from the crankcase

    ????

    Milton

  8. #8
    Join Date
    Sep 2010
    Posts
    19,802

    Default Re: Fuel pump question

    Have you tried opening the low speed mixture needles 1/8th turn at a time ?---That has proven to be a " no money spent fix " on many motors !----And what motor are you working on ?

  9. #9

    Default Re: Fuel pump question

    Motor is a 1982 90 hp mercury

    We had it at lake two times and ran perfect and the third time would not fire up at all.

    Finally got it to run but will not run above about 1/3 throttle.

    We first got it it would not run below half throttle, Installed new stater and it ran fine for a while.

    Milton

  10. #10

    Default Re: Fuel pump question

    Also do not understand why the check valves have a small hole in the center of them

  11. #11
    Join Date
    Sep 2010
    Posts
    19,802

    Default Re: Fuel pump question

    Which " check valves " are you referring to ?

  12. #12

    Default Re: Fuel pump question

    Fuel pump.

    Milton

  13. #13
    Join Date
    Sep 2010
    Posts
    19,802

    Default Re: Fuel pump question

    Post a picture of these holes.

  14. #14

    Default Re: Fuel pump question

    I would have to pull the pump to do that.

    They look to be about 1/64" and look to be original.

    Milton

  15. #15

    Default Re: Fuel pump question

    I would just go ahead and buy two but you have to buy the whole rebuild kit to get them.

    Milton

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