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Odd Choke Behavior

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  • Odd Choke Behavior

    Originally posted 5-02-2015 10:34 AM
    By: pecohen

    I recently had the fuel pump fail on my John Deere lawn tractor (LT166). Once the snow cleared and the days warmed a bit, I replaced the fuel pump and the three hoses coming out of the pump. I also replaced the fuel filter, the air filter the spark plugs and changed the oil while I was at it.

    The engine runs well now, but to keep it running I now have to keep the choke pulled out a bit. This is new behavior - in the past I only need to choke when starting and for a couple seconds afterward. This seems odd to me; I'd think with a new fuel pump and hoses there should be the same or perhaps more gasoline getting to the carburetor, but having to choke more would seem to suggest less is getting there.

    Is this something to worry about? Can someone explain to me what might be happening and how to correct it?

  • #2
    Originally posted 5-02-2015 3:09 PM

    Sounds like there's a blockage in the carb. It's probably time to clean it out. There are small jets and needle valves and if they get plugged up it will restrict fuel flow. With normal air flow into the carb it is making your fuel mixture too lean (weak). Setting the choke part way reduces the airflow and evens it out, but with less power. Taking apart fuel parts upstream may have dislodged some dirt and it found it's way to the carb.

    Many newer carbs are not serviceable and some can not even be taken apart anymore. You can take it off and spray them out and hope for the best. Luckily they are not too expensive to replace (welcome to a disposable society)

    Bowl type carbs have needle valves and very small ports all over. Sometimes you can remove the valves, spray them out well and put it back together, but ethanol in gas breaks down the seals and valve seats. They may need replaced. You can get a carb rebuild kit from a small engine shop. If the valves are adjustable you will need to set them to their initial settings (see manual) and tune it out from there.

    A diaphram type carb (common on Briggs engines) often just needs taken apart, cleaned and put back together. If the diaphram is worn or torn it will need replaced. They are cheap too. No needle valves or ports.


    • #3
      Originally posted 5-10-2015 9:30 AM
      By: pecohen

      Mr T Sounds like there's a blockage in the carb. ..
      I think you are right. Fortunately it seems to have cleared all by itself so it probably was a piece of dirt or something that later flowed through.

      I've been thinking I should try one of those carburetor cleaner additives that you add to the gas, just as a precaution. Have you had any luck with such products?
      Last edited by TransferGuy; 04-01-2019, 05:25 PM.