The 5 Ways You Can Stop Your Lawn Mower From Leaking Gas

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As a homeowner, landscape professional, or friendly neighbor helping to keep the subdivision looking its best, you may be using a walk-behind mower, a riding mower, or a zero-turn mower to cut grass this summer. All three mower types have their own advantages depending on the application, but as long as the equipment uses a gasoline-powered engine, there is a potential for a gas leak. If you’ve discovered a steady drip of fuel pooling on the garage floor or driveway, Repair Clinic has five ways for you to stop your lawn mower from leaking gas. Before we get to those, let’s review how the gasoline you pour into the tank powers the mower.

Following the path the gasoline takes through a mower’s engine

Most gas-powered lawn mowers rely on a four-cycle engine to operate and, just like an automobile engine, a walk-behind mower, riding mower, or zero-turn mower engine are powered by the gasoline poured into the fuel tank. Four-cycle engines will also have a separate sump for the oil needed to keep the engine components lubricated.

Gasoline with high levels of ethanol can be corrosive

Before you even think of removing the gas tank cap, there are some good practices you should be aware of. Lawn mower engines are designed to use gasoline with no more than 10% ethanol, so be careful with the kind of fuel you’re pouring into the tank. Gasoline with higher levels of ethanol can be corrosive and attract water, causing the engine to have starting or running problems. The high levels of ethanol can also damage the fuel system.

Use a fuel stabilizer if storing gas for longer than three months

You should store the gasoline in a clean, sealed plastic container approved for fuel storage. If equipped, keep the container’s vent closed when not in use and always store the container away from direct sunlight. If you anticipate storing the fuel for longer than three months, consider adding a fuel stabilizer when you fill the container.

How gasoline is used to power the lawn mower’s engine

The fuel exits the mower’s gas tank through a fuel filter and flows through fuel lines past a fuel shut-off valve or fuel shut-off solenoid (depending on the engine type). The fuel may also be drawn through a fuel pump (again, depending on the engine type) and past a primer bulb before entering the engine’s carburetor. An intake valve opens as the engine piston travels down the cylinder, creating a vacuum that draws fuel and air through the carburetor where the two mix before entering the cylinder. The piston will travel back up to the top of the cylinder compressing the fuel and air mixture which is then ignited by the spark plug pushing the piston back down the cylinder. As the piston moves back up the cylinder an exhaust valve opens and the combustion gases will then exit through the muffler. This cycle repeats as long as the engine is running.

The 5 ways you can fix a lawn mower gas leak

So, where is that gas leak coming from? Here are the five top reasons your mower may be leaking gas and the parts you can replace to fix the leak:

  1. Worn carburetor bowl gasket – Inspect the carburetor to see if you can detect a fuel leak. Is gas seeping out? Then it’s likely the carburetor bowl gasket is worn out or missing. You can install a new gasket to provide a proper seal for the bowl to stop the leak.
  2. Defective float assembly – Various float assembly components inside the carburetor bowl could be defective as well. The float needle opens and closes the float valve to allow fuel to enter the bowl. If the float needle or the float itself is damaged, the carburetor may continue to fill with fuel until it overflows. You should be able to stop the leaking by replacing one or more of these components. If several float assembly components appear worn, consider purchasing a carburetor repair kit.
  3. Leaking fuel line – One or more of the fuel lines may have developed a leak as well. While it may be tempting to try to patch the line, or trim the damaged section and then attempt to stretch the line to attach it to the nearest valve, this approach is not recommended. Repairing a damaged line will likely lead to the failure of the line once the lawn mower is in use, so it’s best to replace a leaky fuel line with a brand-new one.
  4. Brittle primer bulb – The primer bulb is a small rubber “button” you press to draw additional fuel through the carburetor to prime the engine when first starting. Time and weather conditions will age the primer bulb by making the rubber brittle. This can cause the bulb to develop cracks that will leak gas. Fortunately, primer bulbs are inexpensive and easy to replace, so installing a new one should fix the gas leak problem.
  5. Damaged fuel tank – Last, but certainly not least, you should inspect the place where the gasoline prepares for its journey to the engine: the fuel tank. Does the tank have any cracks in it? Any small holes? Then it’s time to replace the gas tank with a new one (attempting to patch up the old tank is not recommended).
Top Reasons Lawn Mower Leaking Gas — Lawn Mower Troubleshooting

Fix that mower gas leak with a genuine OEM part from Repair Clinic

Do you need a new carburetor bowl gasket to stop your mower from leaking? Or, perhaps, a full carburetor repair kit, or fuel line, or fuel tank? Whatever part will get the job done, it should be an original equipment manufacturer (OEM) part to ensure the repair will last. Repair Clinic stocks thousands of genuine manufacturer parts that are a perfect match for mowers and mower engines carrying names like Briggs & Stratton, Craftsman, Honda, Husqvarna, MTD, Murray, Snapper, Troy-Bilt, Toro, and more. To find the right part that fits your lawn mower, enter the full model number of the mower or the mower’s engine in the Repair Clinic website search bar. Within seconds of clicking the search button, you’ll see a complete list of all the parts compatible with your equipment. You can then use the “Part Category” and “Part Title” navigation filters to refine that list to identify the exact replacement part that will fix the problem.

Install that new part the right way with help from Repair Clinic

Because Repair Clinic wants to be your repair partner, you can find hundreds of “how-to” videos and guides, equipment diagrams, and troubleshooting tips on the Repair Clinic website in the “Videos & Articles” section. Learn how to install a new fuel tank on the model GCV160LAOMY1R280 Honda lawn mower or the correct way to replace a fuel line on the model 09P7020145F1 Briggs & Stratton mower engine. Just like when you need to locate a specific part, enter the full model number of the lawn mower or the mower’s engine in the search bar to discover all the repair help content associated with that specific model.

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