Small Engine Fuel Filter: When and How to Replace It

Not every small engine has an external fuel filter, but if yours does, it's an important maintenance item that's often overlooked.

What does it do? The fuel filter sits in the fuel line between the tank and the carburetor. It catches rust, dirt, and debris from the fuel tank before they can reach the carburetor's tiny internal passages. Think of it as a bouncer keeping the troublemakers out.

When to replace: annually, or sooner if you notice fuel-related performance issues. Some signs of a clogged fuel filter include engine losing power under load, sputtering or stalling at full throttle, slow acceleration or hesitation, and the engine running fine at idle but struggling when working.

Where is it? On push mowers, it's typically an inline filter in the fuel line — a small plastic or metal canister. Some push mowers don't have one at all (the carburetor has a built-in screen instead). On riding mowers, it's usually more visible — a cylindrical filter in the fuel line, often near the fuel tank or engine.

Replacement is straightforward: pinch or clamp the fuel line on both sides of the filter to prevent spillage. Remove the old filter, noting the direction of fuel flow (there's usually an arrow on the filter). Install the new filter with the arrow pointing toward the carburetor. Release the clamps and check for leaks.

What kind to buy? Bring the old one to the parts store for an exact match, or give us the make and model of your engine. Fuel filters are inexpensive — usually $3-8 — and can save you from costly carburetor cleaning.

If your mower doesn't have an external fuel filter, you can add one. We install inline fuel filters as part of our tune-up service when appropriate. It's cheap insurance for your carburetor.