Your Exmark Lawn Mower is Leaking Gas (Fixed!)

You’re smelling gas coming from your Exmark mower, but not quite sure where your mower it’s coming from. Unless you have a significant leak with a puddle on your floor, it can be hard to find a leak because gas often evaporates. You might not actually notice you have a leak until you can smell it.

An Exmark mower can be leaking gas from a stuck float or failed gasket in your carburetor. It is also common for fuel to cause the degradation of plastics over time causing gas to leak from the fuel pump, gas tank, and fuel filter.

Keep reading and I’ll share with you all of the places your Exmark can begin leaking gas.

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

7 Reasons Causing Your Exmark Mower to Leak Gas

Exmark Carburetor is Leaking Gas

Your carburetor is a good place to start looking for a fuel leak on your Exmark mower. Carburetors get dirty with gummy and crusty buildups that can cause the parts in your carb to not function correctly.

This is the place fuel is stored after it leaves your gas tank. When parts get stuck or your gasket fails, your Exmark will begin leaking gas.

Gasket failure in the carburetor bowl on an Exmark Mower

The first place to check on your carburetor for a leak is the gasket on the carburetor bowl. It’s common for this gasket to become hard and brittle over time due to the location of the gasket.

It’s located right next to the engine so it heats up when the engine runs and cools down when it is not in use. This constant heating and cooling put a lot of stress on the gasket causing it to lose its sealing ability.

The gasket is located between the carburetor bowl and the carburetor. It kind of looks like a rubber band. If you find a leak in this area, you will have to replace the gasket. This is a pretty simple procedure.

You will need to buy a replacement gasket. To find a good replacement, you’ll need to locate the model and spec number from the engine.

Unless you are using an Exmark branded engine on one of the Exmark Radius models, you’ll have to use the numbers off the side of the engine cover to ensure you get the right gasket for your Kohler, Kawasaki, or Briggs engine.

Once you have the new gasket, begin the repair by shutting off the fuel supply. Use the fuel shut-off valve under your gas tank. If your mower doesn’t have a valve, use a clamp to clamp the fuel line.

Once the fuel flow has been stopped, remove the screw and remove the carburetor bowl. Have a rag available to catch the remaining fuel in the bowl. Remove the old gasket and place the new one on the bowl. Reinstall the carburetor bowl.

Tighten the screw to hold the bowl and carburetor together. Wipe down your carburetor, turn on your fuel supply, and check for any additional leaks from your carburetor.

If you notice more leaks, check your carburetor float and needle. These are also items known to fail. They can get stuck and cause fuel to leak.

Stuck float in an Exmark mower’s carburetor

Next, look for a fuel leak near the air intake port. When you find a leak in this area, you could have a stuck float that can no longer regulate fuel flow into the bowl. Fuel keeps flowing into the carburetor bowl and then overflows out of the carb when you have a stuck float.

Take your carburetor apart when you find a stuck float to determine the actual cause of the failure. You may be able to clean the carburetor to keep the float from sticking.

You may also have to rebuild it to get your carburetor to work right. Read the steps to clean your carburetor in this article.

Stuck float needle on an Exmark Mower

The last thing you should check on your carburetor is the float needle. The float needle works in conjunction with the float to keep gas flowing into the carburetor bowl. If the needle gets stuck, it will need to be repaired.

You will have to take your carburetor apart to fix the float or you can take it to your local small engine mechanic to have the carburetor rebuilt.

Some Exmark owners tap on their carburetor gently with the rubber handle on their hammer or with a rubber mallet to free the needle. This does work a time or two, but it is only a temporary fix.

Exmark Fuel Filter is Cracked or Deteriorating Causing a Leak

Fuel can cause degradation in plastics like that used for an Exmark inline fuel filter. The filter can begin leaking at the seams when your filter deteriorates. It can also leak if the plastic is cracked. A leaking fuel filter needs to be replaced.

Be careful when removing the ends of the inline filter from your fuel lines as the plastic can become soft and break off. You can find a replacement inline fuel filter online or at your local hardware store.

The type of fuel you use in your Exmark mower and how you store it can affect your fuel system. Read more about the effects of ethanol and the best way to stabilize your gas in my article on Exmark lawn mower gas.

Bad Exmark Fuel Pump Can Begin Leaking Gas

Your vacuum fuel pump can wear over time because the makeup of fuel today can degrade plastics causing leaking at the plastic seams. When the plastic is compromised, your fuel pump is no longer able to build the pressure it requires to pump fuel to the carburetor.

A fuel pump with a fuel leak must be replaced. You can purchase one at your Exmark dealership or online for your Briggs, Kawasaki, or Kohler engine. An aftermarket fuel pump I’ve had good success using and have sold to my customer over many years is this one.

Failed Seams on Your Exmark Fuel Tank Will Begin to Leak

Fuel tanks used on Exmark lawn mowers are made with high-density polyethylene. The seams on the tanks can fail to cause your fuel tank to leak. The best solution is to replace your fuel tank with a new tank.

Exmark Fuel Shut-Off Valve is Prone to Leaking Gas

Your Exmark mower may have a valve on the bottom of the fuel tank called the fuel shut-off valve. Its function is to start and stop fuel flow. Your valve can leak whether it is made of plastic or metal. You need to replace your fuel shut-off valve when you find it leaking gas.

Old Exmark Fuel Lines Can Become Dry and Leak

Fuel lines can become dry and brittle with age. They can develop cracks where gas can leak from your Exmark.

Another place that is known to leak is in the areas where clamps are used to secure your fuel lines. The clamps can either be loose or puncture the hose causing fuel to leak out of your Exmark’s fuel line.

Any cracked fuel lines need to be replaced. This may also be a good time to replace your fuel clamps if your mower uses a pinch-style clamp. I like using a worm gear clamp because they are less likely to pinch your lines and cause leaking.

Bad Exmark Gas Cap Seal Can Cause Leaking

When your gas cap doesn’t seal, your Exmark can form a leak around the cap. If you smell gas and went through all the above checks for a gas leak and still can’t find it, you should definitely check the seal in the gas cap.

A leak around the cap will leave a wet spot for a short time before it evaporates and doesn’t leave a sign of leakage. To determine if your cap is sealing, rock your mower back and forth to splash gas up around the cap area and watch for wet areas to develop around the cap.

Replace a gas cap with a new cap when you see signs of gas around the cap on the outside of the fuel tank.