Anonymous asked in Cars & TransportationMaintenance & Repairs · 7 months ago

Gas lawn mower problems?

I have had it running but not now. I have cleaned the carb bowl and fuel lines. The gas does not seem to be filling the bowl, although there was a small amount of gas in it (after I checked). The gas flows by gravity from the tank and the needle valve has been cleared. It will start of a starter fluid but not continue.

I would consider a replacement carburetor but I don't understand what is going on? Or what is wrong?


I have one bit of information, that when first cleaning the float bowl, there was solid flaky material which came off the float.

5 Answers

  • 7 months ago

    The tank need to be vented so gas can drain out by gravity. Try removing the gas cap and give that a try. The cap is supposed to be vented, but the vent may be clogged.

  • 7 months ago

    The float needle seats in an o-ring to stop the gas supply when the carb bowl is full. That o-ring swells up from the ethanol on the gasoline. When the o-ring swells up it reduces the size of the o-ring hole and can completely shut off the gas supply even with the needle open. I use a small drill bit and ream the o-ring by hand to open it if it's not replaceable The float level may need resetting after doing this.

    Source(s): Mitsubishi Master Tech
  • 7 months ago

    Remove the nut holding the float bowl in place. Check it to see if it has little orifices in it. If it does, clean it out with small wire thoroughly. those holes get plugged up with crud if the gas gets too old. Engine wont run if it's plugged up.

  • 7 months ago

    The engine runs on starter fluid so this is a fuelling problem. not mechanical or ignition.

    1. Clear the breather vent/hole in the fuel cap. If air can't get enter the fuel tank to replace the fuel flowing down to the carbie, it creates a vacuum in the tank strong enough to stop the fuel flow. To test if this is the problem, try running the mower with the fuel filler cap removed.

    2. If it checks out, remove the fuel line at the tank end to test if fuel comes out of the tank. If good, put it back like it was

    3. Then remove the fuel line at the carbie end and see If fuel is reaching the carbie end of the fuel line. If good put it back like it was.

    4. If your carbie has a drain screw at the bottom of the bowl, remove it to see if fuel is getting into the bowl. If it isn't, adjust the float height. Make sure the float opens and closes and is able to move freely in the bowl. If your carbie has no drain screw, remove the float bowl. It might be easier to do this test on a bench with a remote fuel supply. While you're there, make sure all the jets are clear and that the throttle opens and closes like it should.

    • Lv 7
      7 months agoReport

      I did do most of that but think maybe the float is where I should focus next.

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  • L.N.
    Lv 7
    7 months ago

    Some carbs have a little flapper valve diaphragm that is vacuum operated and acts as a fuel pump. The rubber gets damaged by ethanol in gasoline or dries out and stops working. Also check the fuel filter. They are often inside the gas tank.

    • Lv 7
      7 months agoReport

      I wonder if I have this? There is a second hose, a softer one which goes to a plastic valve. that's as far as I can see.

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