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Briggs: What are some common fuel supply problems?



What are some common fuel supply problems?

A big part of ensuring a smooth running engine is keeping your carburetor and linkages clean and well adjusted. The linkages attached to the carburetor's throttle and choke plates can bind or stick when dirty. Constant vibration and wear can affect the settings of the carburetor's mixture screws.

And with all of the grass, twigs and other debris that a small engine encounters, it's not surprising that even passages inside the carburetor eventually pay a price. Deposits inside the carburetor can clog fuel and air passages and reduce performance or stop the engine altogether.

Luckily, you can take care of many of these problems quickly and easily - often without even removing the carburetor from the engine. Commercially available carburetor cleaner comes in convenient spray cans for periodic cleaning both inside and outside the carburetor.


An engine that does not start or performs poorly may have a carburetor problem. The source of the problem may also be in the fuel valve, filter or pump. Start by checking these possible sources:

1 Remove the air cleaner and inspect the choke plate mounted on a shaft at the opening of the carburetor's throat (image A)id="blue">. Check that the choke plate closes easily and completely. A choke that does not move freely or close properly can cause difficulties in starting.

2 Spray a small amount of carburetor cleaner on the shaft of a sluggish choke and into the venturi to loosen grit (image A)id="blue">. Debris in the carburetor often causes performance problems.

3 Open the fuel valve (if equipped), located at the base of the fuel tank where the fuel line is attached. Remove the line and check for blockage (image B)id="blue">. Fuel will not reach the carburetor if the fuel valve is closed.

4 If the engine is equipped with a fuel pump, make sure it operates properly (see Servicing the Fuel Pump FAQid="blue">).

5 Remove and inspect the spark plug. A wet plug may indicate over-choking, water in the fuel (see Servicing the Fuel Tank FAQid="blue">), or an excessively rich fuel mixture. A dry plug may indicate a plugged fuel filter (see Servicing the Fuel Filter FAQid="blue">), leaking mounting gaskets on either end of the caruetor, or a stuck or clogged carburetor inlet needle.

6 Pour a teaspoon of fuel into the spark plug hole (image C)id="blue">. Screw the spark plug back in and start the engine, If it fires only a few times and then quits, assume a dry plug condition and consider the causes of a dry plug, listed in Step 5.

For additional information, please visit these related FAQs:

Adjusting the Idle Speed and Mixtureid="blue">

Adjusting the High Speed Mixtureid="blue">

Adjusting the Choke Linkageid="blue">

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