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fuel bowl

Discussion in 'Early CJ5 and CJ6 Tech' started by johnsotd, Aug 28, 2015.

  1. Aug 28, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    I have the dual diaphragm fuel pump with the glass bowl on top. When I turn the engine off the fuel level in the glass bowl slowly drops.
    The motor is in the rolling chases state and is not connected to the tank. I disconnect the hose from a lawnmower gas can when I turn the engine off. Is this normal? What is the routing of the fuel thru the pump?
     
  2. Aug 28, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Does the level disappear? If so it might be going into the crankcase. Pull the dipstick and check the oil for gas fumes or thinning.
     
  3. Aug 28, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    If I knew the route of the fuel I might figure it out. Oil looks fine with no gas smell.
     
  4. Aug 29, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I went out and experimented with old pumps I have after my original post so this is modified now. Fuel pumps have check valves, either one or two on the suction, and one or two on the discharge. Depends on the design. When the fuel pump is actuating fuel is pulled in by the suction valve/s, and it opens and closes accordingly with the diaphragm action. When the pump is not actuating fuel should remain in the bowl at least level with the fuel intake section. If there is nothing stopping it fuel can run right back out the intake line if it is higher than the intake. The way the fuel intake line is routed could influence the level too, and I suppose could keep the level above the intake section. The created pressure forces the fuel through the discharge side, so if not actuating and creating pressure then it shouldn't be going the discharge side. Can you post a picture of your fuel pump please?

    Note: I should have written that when the fuel pump is actuating it pulls or pushes fuel and the check valves open and close accordingly with the diaphragm action.
     
    Last edited: Aug 29, 2015
  5. Aug 29, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
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    The glass dome found on the 134 Willys AC brand fuel pump is actually an inverted fuel sediment bowl.
    The 134 Willys mounting actually inverts the AC fuel pump sediment bowl and it becomes a dome.
    Inverted as a dome the glass is never quit full of gasoline.
    It will normally maintain a level of gasoline in the dome that is within 1/4" from being completely full.
    If it bleeds down below that level then either the bowl gasket is leaking or one of the two pressure/check valves are leaking.
     
  6. Aug 29, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    [​IMG]
    The large hose is my temporary fuel line.
    Hope this helps.
    Thanks
     
  7. Aug 29, 2015
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    Like Oldtime says.

    As Glenn said, a leaky diaphragm is also possible. Or the bowl dome gasket.

    You could try pushing fuel through it, possibly that could flush the valves clean. Or put a vacuum on the inlet side, see if it holds.
     
  8. Aug 29, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    When the picture is blown up you can see (inside the glass dome) a little squarish section next to the dome in the middle, which is higher and has the screen at the top. When not running fuel can run back out of the bowl through the line into your container, but it shouldn't drop below level with the top of that section which is part of the inlet, as it is directly in line with the inlet hose.
     
  9. Aug 29, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    I took the top off and the two backpressure valves seem to work OK when I blow in and out on the lines but they may leak down when the pressure is off.
    To morrow I will plug the temporary inlet hose after I run the engine. If it leaks down then I will assume it has to be a leaky check valve,
     
  10. Aug 30, 2015
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    In the absence of noticeable fuel in the oil and the absence of a puddle under the pump, the likelihood of the a bad valve is high. A visual inspection and just pushing on a valve will not tell you if it is bad. There could be excessive wear around the edge allowing fuel to creep back down the inlet line or the spring could be weak from age.
     
  11. Aug 30, 2015
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Huh? If you plug the inlet, it can't leak down through the check valves. Or do you mean you will remove it and plug just the tank side?
     
  12. Aug 30, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    His shouldn't leak lower than the little inlet section in the top of the pump. Check valve in his shouldn't cause the level to disappear.
     
  13. Aug 30, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    Tank side. Thanks
     
  14. Aug 30, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    BTW Before use the pump was rebuilt with a kit from Walcks.
     
  15. Aug 30, 2015
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    Are the valves held in place by an hour glass-shaped plate and two screws? If not, and the rebuilder had to pry out the old valves, there may be leakage past the valve body due to damage to the orifice in which the valve fits.
     
  16. Aug 31, 2015
    johnsotd

    johnsotd Member

    Senatobia, MS
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    I plugged the tank line after running the engine and the bowl stayed full for about three hours. The bowl was still half full after sitting overnight. There was no visible fuel in the bowl this afternoon but there was enough fuel to start and run the engine for a short time. Believe it or not new bowl gaskets are available at my local Auto Zone. hopefully that will fix the problem.
    Thanks for all of the help!
     
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