When your lawn mower engine isn't starting or it stops running once you get it started, this often points to a clogged fuel line. A fuel line on a lawn mower connects to the base of the gas tank and runs to the side of the carburetor. If this line has debris or gummed-up gas in it, your mower engine won't run. Cleaning the fuel line once a season is a good idea to prevent engine damage from dirty gas.
Put on your goggles, and pull the spark plug cap off the spark plug. This is a safety precaution when you are working on a mower engine to prevent the engine from starting accidentally while you are working on it. Push the spark plug cap back onto the spark plug once you are finished working on the mower.
Look at the gas cap to see if there is a pin hole in the center of it. Unscrew the gas cap. Look under the cap to ensure the pin hole is clear of obstructions and wipe away any debris. The pin hole allows air to flow into the tank and prevents vapor lock in the fuel system. All lawn mower gas caps should have this air pin hole, so buy a new gas cap that has the pin hole if the current one doesn't.
Squeeze the clamp holding the fuel line to the base of the gas tank with the pliers. Slide the clamp down the fuel line several inches. Repeat this on the other end of the fuel line attached to the carburetor.
Pull the fuel line off the side of the carburetor and the base of the gas tank. Position the bucket under the gas tank to capture any gas.
Unscrew the clamps holding the fuel filter to the center of the fuel line with a screwdriver. Remove the fuel filter from the center of the fuel line hoses.
Spray WD-40 into the fuel line hoses that were attached to each side of the fuel filter. Spray the canned air into each fuel line hose to blow out any debris or gummy gas.
Place the new fuel filter in between the old fuel line hoses you cleaned, and clamp the fuel filter back into place in the middle of the fuel line hoses.
Pull the screen out of the base of your gas tank outlet. Spray it with WD-40 to remove any debris or gummy gas. Push it back into place.
Slide one end of the fuel line onto the base of the gas tank and one onto the side of the carburetor. Squeeze and slide the clamps onto the end of the fuel line to hold it in place. Fill the gas tank with gas.