Lawn Mower: Leaks Gas

Fuel leaking from your lawnmower is a potentially dangerous problem that should be addressed immediately. A lawnmower fuel leak is often caused by the carburetor. The carburetor stores a small amount of fuel in the bowl on the bottom of the carb. The fuel is regulated into the bowl by a metering needle. The needle attaches to a hinged float. As the fuel level in the bowl drops, the float lowers, which opens the metering needle allowing fuel to flow into the bowl. If the metering needle becomes stuck in the open position, fuel will continue to flow until the fuel tank is emptied. The most common reasons the metering needle becomes stuck open are debris and corrosion. If a tiny stone or piece of grass gets past a damaged fuel filter it can easily stick the metering needle in the open position. Corrosion around the metering needle can cause it to stick to the walls of the cylinder it slides up and down in. Corrosion is formed when old gas is allowed to sit in the carburetor for a period of time. Damage will begin in as soon as 30 days when the mower sits unused. Recently, corrosion has become more of a problem as more ethanol is blended into our fuels. Ethanol is a type of alcohol. Alcohol naturally attracts water. When fuel sits unused, the ethanol will bond with humidity in the air. This mixture forms acetic acid. The acid will attack the aluminum body of the carburetor, forming corrosion. In most cases, fuel leaks caused by the carburetor can be fixed with a thorough cleaning. You will need to remove the carburetor from the engine and disassemble it into its various components. Remove the bowl, float, and metering needle. Pay close attention to the condition of the metering needle and the cylinder it fits up into. While the carburetor is open, it is a good idea to clean its other components, even though they aren�t related to the fuel leak. Remove the main jet and the emulsion tube above it if possible. Not all emulsion tubes are removable. On the outside of the carburetor, remove the pilot jet or pilot jet cover screw. Now you can clean the carb body and each of the components you removed. Use carburetor cleaner to spray each piece clean. Be sure to spray carb cleaner through all of the tiny openings in the carb body as well as the main jet, the pilot jet, and the emulsion tube. Never insert anything made of metal into the openings to assist cleaning. These openings are very precise and can easily be damaged. It is okay to use something soft such as fishing line to clean the openings and passages. An alternative method for cleaning the carburetor is to use an ultrasonic cleaner. The ultrasonic does an amazing job of cleaning all the nooks and crannies of a carburetor. If you do a lot of do-it-yourself repairs, a small ultrasonic cleaner might be a good investment. Inspect the condition of the bowl gasket and the bowl screw seal and replace them as needed. Reassemble the carburetor and reattach it to the engine. Before you put your mower back into service there is one more potential problem you will need to attend to. When metering needle sticks open, the fuel completely fills the bowl and begins to push out through the emulsion tube into the throat of the carburetor. From here, some of the fuel leaks out the front of the carburetor through the air cleaner. This is the puddle of gas you see on the ground. Often an equal amount of gas or even more leaks from the carburetor and back into the engine. It leaks past the intake valve into the cylinder. It then seeps past the piston rings into the crankcase. It mixes with and dilutes the engine oil in the crankcase. The diluted engine oil can�t properly lubricate the engine, which will lead to serious engine damage if the mower is run in this condition. Whenever you fix a stuck metering needle it will be necessary to also change the engine oil to remove the potentially diluted oil.

If your lawnmower is leaking fuel you might have a damaged fuel tank. Fuel tank cracks are usually the result of an accident. They can be caused by the tank hitting a low-hanging shrub branch. If something falls on the lawnmower the tank can be cracked. With some lawnmower designs it is possible for the fuel line to snag on something, such as a shrub, which can break off the fuel line fitting from the tank. Replacing the fuel tank will vary greatly depending on the design of the mower. Some tanks are a separate piece and are easy to remove, some are located under the engine shroud, and some are part of the engine shroud. Regardless of the design the first step is to drain any fuel that might still be in the fuel tank. If the tank is exposed, you can simply remove the fuel line from it and then remove the tank from its mounting. If the tank is under the engine shroud, you will start by removing the shroud. Some designs might require you to remove the starter assembly first. Once the shroud is removed, you will have access to the tank and can remove the fuel line. Then remove the tank from its mounting. Most mowers that have the tank integrated into the engine shroud will require you to first remove the starter assembly. Next remove the fuel line. Now you can remove the shroud and tank assembly from the mower. Removing and replacing a lawnmower fuel tank is usually an easy repair that doesn’t require a lot of tools. However, it is a repair that can save you lots of money.

Fuel leaking from your lawnmower could be caused by a damaged fuel line. Most fuel line problems are simply the result of aging. As fuel lines age they begin to harden and will eventually crack or break. When fuel lines harden they will sometimes no longer make a tight seal around the fittings on the fuel tank, carburetor, and fuel filter which can lead to leaks. The fuel lines on a lawnmower are usually exposed which makes finding leaks easy. Replacing the lines is also easy. Start by draining any gas that is in the fuel tank. The fuel lines are typically held in place with spring clamps. Use pliers to loosen the spring clamps and slide them down the fuel line, away from the fitting. The line can then be pulled from the fitting. Most fittings are barbed and sometimes the fuel line will stick to the fitting so a pair of pliers is helpful in removing the line. Start by rotating the line around the fitting to break it free. Then the line can be pulled from the fitting. Now you can install the new fuel line. Some fuel lines will need to be cut to length. If the old line is intact, you can use it as a template to cut the new line. If not, attach one end of the line to the first fitting and then route the line to the second to determine the length, then cut to fit. Once the line is sized, slide a fuel line clamp over both ends of the line. The fuel line will simply push onto the fittings. If it doesn’t want to slide into place, you can use a small amount of engine oil to lubricate the fitting first. Once the line is in place on the fitting, use the fuel line clamp to secure it. Replace each line in the fuel system in the same manner.