Bores filling up with fuel

Discussion in 'Outboards' started by valvebounce, Jun 11, 2019.

  1. valvebounce
    Joined: Dec 2010
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    valvebounce Senior Member

    I have just changed the fuel pump on my 1999 25hp outboard.
    It is impossible to pull the engine over with the cord because the cylinders have filled up with fuel.
    Anybody got any ideas?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    I doubt that, V. There must be another problem. The motor is not seized ? Take out the plugs and have a look at them for rust on the electrode. Maybe the recoil start has locked up. Can you get your hand on the flywheel to see if it is free ?
     
  3. valvebounce
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    valvebounce Senior Member

    Gooday Mr E,
    The cylinders are full of fuel.With the plugs out the engine pulls over easily.
    When I turn it over,fuel squirts out of the plug holes.I looked in the plug holes,
    and they were brimming over with fuel.
    If I pump the bulb on the fuel line,it doesn't get completely solid,and it's possible to keep pumping.
    The end result is the fuel being pumped into the cylinders.
    I am wondering if this new pump has been assembled wrong.
     
  4. JamesG123
    Joined: Mar 2015
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    JamesG123 Senior Member

    Carb float valve bad or even missing? It would help if you gave a specific make and model.
     
  5. valvebounce
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    valvebounce Senior Member

    The outboard is a 1999 25hp Johnson-J25RLEEB
    The fuel pump is brand new.I have had the carb off and cleaned it with carb cleaner(removed the jets)
    I reset the float height and checked the float pin and clip.
    I took it for granted the pump would be ok with it being new.
     
  6. JamesG123
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    JamesG123 Senior Member

    Pump seems to be working just fine. lol
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    There would be fuel coming out all over if the needle valve wasn't working.
     
  8. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    A couple of things to look at.

    First, when you pump the bulb is it overflowing into the carb??? Typically if the float setting is wrong you will be able to pump hard and it will overflow out the front of the carb or come out of the jets.

    Second, if you have a leak in the fuel pump diaphragm it will leak directly into the crankcase and that can directly fill up the cylinder, usually the one that is used for the fuel pump, but if you pump in a ton of fuel and have a leaking diaphragm you can fill them both up in pretty short order.

    I would look at the carb first and make sure that when you pump the bulb it isn't coming out of the jets. If it isn't, then look at the fuel pump diaphragm. If you want to double check the carb, route the fuel hose to bypass the fuel pump and if it doesn't pump up hard then it's the carb. If it pumps up hard then the diaphragm is leaking.

    More than likely one or the other...
     
    BlueBell likes this.
  9. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Did it run fine after the carb rebuild?
    What other work was done after it last ran fine?
     
  10. valvebounce
    Joined: Dec 2010
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    valvebounce Senior Member

    I had put one of the pressure pipes onto the fuel pipe connections on the pump,(what a dope,Haha)
    The engine runs ok now,but is hard to start.
    I think I may have got the wrong pump.On the original pump,the dia of the outlet pipe to the carb had a smaller brass fitting at the pump end,I changed the bass fitting on the new pump for the smaller dia one off the old pump.
    when I checked,the new pump was for 50hp to 120hp engines.It does fit exactly the same as the old pump.
    What is happening now is,the engine idles perfectly,but if I increase the revs,the engine stutters,if I reduce the revs
    it goes back to tickover no problems.
    The sight bulb on the inlet pipe empties almost when I rev it up.The tank is well vented.
    When I bought the engine it had the same problem,which I thought would be a simple fix.
    I bought a new pump thinking that was the problem.
    When I rev the motor it seems to misfire before the revs pick up,and then almost stalls until I come off the revs.
    I am wondering if it is not only a fuel problem,but an ignition problem as well.
    It's got me beat,and the fishing season is in full swing.
     
  11. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Doesn’t sound like a fuel pump problem.

    If the pump is working, but not well, there is normally a lag in between throttle adjustments and the poor running. It takes a short time to use up the fuel already in the float bowl before you see any running problems. And symptom is normally the motor dying, or trying too, not stuttering or misfires.
     
  12. Yellowjacket
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    Yellowjacket Senior Member

    If the fuel sight glass is emptying as you rev it up, it's starving for fuel. Check the fuel line to make sure it is not flaking apart inside. If it is good, then take the fuel fitting off of the tank and run the motor from a gas can with the fuel hose stuck in it. Most outboard fuel tanks have a screen on the tank to keep crap from entering the fuel line. If gas goes bad in the tank, and then the tank is filled some of the varnished fuel will come off the bottom of the tank, and the tank can look clean, but the gunk ends up in the fuel strainer and you will starve at high power. If the motor runs fine with the hose dipped into a gas can find out where the restriction is.
     
  13. valvebounce
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    valvebounce Senior Member

    Thanks YJ,
    After thinking about it,I think you are probably right.I have 3 fuel tanks,all with quick fit hoses so I can interchange the tanks.The hoses have click in connectors with non return valves in them.I have had trouble with the non return valves sticking in the past.
    I'll go through the procedure you suggested and check it out.
    I use 99 octane fuel,and it has no additives.
    It could possibly be the pump up bulb failing,they have a non return valve in them as you probably know.
    Thanks for your time,I'll keep you posted."V"
     
  14. valvebounce
    Joined: Dec 2010
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    valvebounce Senior Member

    Than
    Thanks for your time O,I'll be glad if it's not an ignition fault.I think YJ may have sent me the answer,I'll be checking out what he suggested."V"
     

  15. valvebounce
    Joined: Dec 2010
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    Location: manchester uk

    valvebounce Senior Member

    Is it possible to overpump the bulb to the point where the engine gets too flooded to start?
    Could I be forcing the fuel up the emulsion tube in the bowl of the carb and flooding the engine?
    I suspect I have a spark plug that is faulty,I suppose that could be the reason for the bad starting.
     
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