HELP! My Carb is Clogged with Something!

pekoeSeptember 12, 2006

I put the dregs of my gas in my lawn mower and the motor cut out. The filter was clogged, so I bought a new one. Now the mower will start if I spray starting fluid in, but dies. I have verified that gas is getting to the carb, so I believe a jet is clogged.

I had thought of blowing compressed air in, but can't get a compressor. I'm thinking of removing a jet screw, but I can never seem to get the carb adjusted correctly.

Any other strategies, or am I missing something?


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wise_guy(NW MN)

Do not blow compressed air into your carb while it is still assembled. This could blow out seals and/or crunch your float.

Remove the bowl and bowl nut. The first orifice your fuel will go through is located in the bowl nut. That is the most likely spot for a clog. Also, remove your needle and rinse off any particles from it and the fuel inlet tube.

    Bookmark   September 12, 2006 at 10:07AM
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Am I correct that the bowl and bowl nut are on the bottom of the carb? Is this adjustable, or do I remove the nut, clean and tighten? Also, any clue about which screw is the needle? Is it also adjustable?


    Bookmark   September 12, 2006 at 10:27AM
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If it's head looks like a standard bolt head with no movable screw in the center, then yours is not adjustable. Remove it, clean it and reinstall.

    Bookmark   September 12, 2006 at 11:19AM
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wise_guy(NW MN)

I can't answer all those questions. It depends on what type of engine you have and how old it is.

This is a conventional bowl-type carb, right? Not a pulse-jet style (ones mounted directly to gas tank on old B&S engines).

If conventional style: bowl is located on the bottom of the carb and is removable by removing single central nut (bowl nut). The bowl nut will have holes in it for fuel regulation. Either adjustable (called a jet) or non-adjustable (called an orifice) depending on age and EPA regulations. Some newer engines still have a semi-adjustable low-speed circuit. But you don't have a low-speed circuit problem. It sounds like you aren't getting any fuel up the main nozzle.

    Bookmark   September 12, 2006 at 11:20AM
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Sorry - it is a 17 HP Briggs and Stratton OHV on a Craftsman 48" deck riding mower - approx 6 yrs. old. I am at work and not looking at the motor right now.

There appears to be a wire attached to the carb, and not the typical big nut at the bottom. The rubber gas line is attached to a white, square pivot that connects to the side of the carb.

    Bookmark   September 12, 2006 at 11:29AM
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wise_guy(NW MN)

You're carb will not have a high speed fuel mixture adjustment. I believe it still has a low speed adjustment with a limiter cap on it. I would not mess with the low speed adjustment.

The thing at the bottom of your bowl is a fuel shut-off solenoid that cuts off the fuel supply to the main nozzle when the key is turned to the off position. Cycle the key from off to run a few times and listen. If it is working properly, it should make a tick sound when you move to run and a tlock sound when you switch back to off.

To remove the bowl, you must disconnect and unscrew the fuel shut-off solenoid. Once the bowl is removed, you will find orifices in the side of the casting that the fuel shut-off solenoid screws into and/or an orifice directly on the bottom of the main nozzle tube. These may be plugged. Also verify that fuel is entering the bowl through the needle valve and that the needle valve is able to stop the flow with a gentle upward push.

Also check again that the fuel shutoff solenoid is working properly. With the solenoid out and electricall connected, ground the case of the solenoid against the engine and operate the ignition switch. You should see the plunger moving in and out on the fuel shutoff solenoid.

Oh... and of course: check the simple things first! Check the gas tank vent (make sure it is not plugged) and check the spark plugs. If it is a fuel problem, the spark plugs should be dry after cranking the engine over.

    Bookmark   September 12, 2006 at 12:43PM
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You said that you dumped the last bit of gas from the can into the fuel tank! you probably also dumped any water (condensation) into the fuel tank, and thence into the carburetor and intake manifold, causing a no-start condition.
Since you are possibly not familiar with mechanical terms pertaining to things mechanical, i'd suggest taking it to a service/ repair facility! It will save you money in the long term, because, with you not being well-versed in mechanical work, you could end up spending lots of gold to have it fixed right!
HTH Rustyj

    Bookmark   September 12, 2006 at 1:06PM
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Thanks, Wise Guy - will try tonight.

    Bookmark   September 12, 2006 at 1:36PM
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I drained the tank and put fresh gas in. Squirted some starter fluid in and it fired right up!

Thanks, all!

    Bookmark   September 12, 2006 at 3:55PM
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Will miracles never cease?

    Bookmark   September 12, 2006 at 4:31PM
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