My Briggs & Stratton 6.5 HP Quantum Is Leaking Gas From the Air Filter

Shutoff Valve

• The shutoff valve on your Briggs & Stratton Quantum prevents gas from escaping into other parts of the lawnmower when the engine is not in use. This valve automatically closes when the engine stops running. Gas that's leaking from the air filter may indicate that the valve is not working correctly. It may be staying open all the time, allowing gas to leak out. You may need to replace this valve to keep it from sticking again since this problem often indicates a worn-out valve that will continue to fail more frequently.

Fuel Float

• The fuel float is designed to maintain pressures inside the carburetor by closing off the system at a certain fuel level as the carburetor operates. If the fuel float becomes stuck, a problem similar to a stuck shutoff valve will occur. Fuel will be able to escape from the carburetor, and its main exit is the air line, which is blocked by your filter. The result is fuel leaking from the filter and a float that needs to be cleaned or replaced.

Other Carburetor Problems

• The fuel float is not the only problem the carburetor can develop, which may cause the lawnmower to leak gas out of the air line. Dirty carburetors, cracked components and fuel quality can cause issues of their own, which may result in leaking fuel. Replacing the carburetor may be required but be careful. Sometimes taking apart the carburetor or installing a new one can cause these problems instead of correct them.

Fuel Line Issues

• If your fuel filter has become blocked by debris or the fuel line connections are failing, gas may start leaking from the mower. Sometimes fuel lines simply become too old to properly carry fuel without cracking and leaking. While this rarely causes fuel to leak directly from the air filter, it can cause leaks in nearby engine components, which may be fooling you, so run through a line check as well as a carburetor check.