Why is there a gas leak by the small engine air filter & vent tube?

Gas leaks around the air filter usually indicate problems with valves inside your engine and how it is processing gas. Read below to learn what specifically could be causing your lawn mower and small engines to leak gas through the vent tube and air filter.

WARNING: Fuel and its vapors are extremely flammable and explosive. Always handle fuel with extreme care. Never attempt to start or operate an engine or machine that has a fuel leak.

Always read the engine and equipment manual(s) before starting,operating, or servicing your engine or equipment to avoid personal injury or property damage. See an authorized dealer or contact Briggs & Stratton if you are unsure of any procedure or have additional questions. Find all Engine Safety Warnings


Possible Causes for Gas Leaks by the Air Filter

Fuel Shut-Off Valve Problems

Small Engine Gas Leak by Briggs and Stratton

Gas leaks around the lawn mower air filter can indicate your engine valves are not working properly. If your engine has a fuel shut-off valve, ensure that this valve is closed when the engine is not in use.

Check for any signs of valve damage that could prevent it from automatically closing when the engine stops running. If it stays open and sticks, it could indicate that the valve is worn-out and in need of a replacement.

Small Engine Carburetor Issues

Another common cause of gas leaking around air filters is due to carburetor issues.

  • Fuel Float Issue: Designed to maintain pressure inside the carburetor by closing off the system at a certain fuel level, the fuel float can become stuck, resulting in gas escaping from the carburetor into the vent tube & air filter
  • Damaged or Dirty Carburetors: If your engine’s carburetor is dirty or cracked, then it could also lead to leaking fuel around the air filter

Cleaning or replacing your carburetor or fuel float may be necessary, but make sure to understand how to troubleshoot or service carburetors before taking action.

For engine inspection or gas leak help, contact one of our Briggs & Stratton Dealers near you.