There’s a strong fuel odor lingering in your garage. You have identified a fuel leak is coming from your mower, but you’re not sure exactly where. Finding a fuel leak can be a little difficult once a mower has been sitting a while and the fuel evaporated into the air.
A zero turn lawn mower can begin leaking gas from the carburetor, fuel pump, fuel lines, fuel filter, or fuel shut-off valve. A fuel leak can also develop in the gas tank or as the result of a bad seal in the fuel cap.
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Follow all safety instructions provided in your equipment operator’s manual before 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 Places Your Zero Turn Lawn Mower Can Begin Leaking Gas
Carburetor
The carburetor is the place where a little fuel is stored after it leaves the fuel tank. There are a few components to look at when you notice the carburetor is leaking.
Carburetor Bowl Gasket
You will find a gasket located between the bowl and the carburetor. It kind of looks like a rubber band. Because of its location near the engine, it can become dry and brittle.
The carburetor is located next to the engine so the gasket becomes hot when the engine is running and cold when it is not.
This temperature change stresses the gasket causing it to lose its sealing capability. When you find a leak between the bowl and the carburetor, the gasket must be replaced.
Replace the carburetor gasket:
- Shut off the fuel supply using the fuel shut-off valve or crimp the fuel line.
- Wipe off the dirt around the carburetor.
- Remove the screw at the bottom of the carburetor and remove the bowl. Have a rag available to catch any remaining fuel in the bowl.
- Remove the old gasket around the bowl.
- Replace with a new gasket. Be careful not to get any carburetor cleaner or other material on the gasket.
- Reinstall the bowl and tighten the screw to hold the bowl and carburetor together.
- Wipe down the carburetor.
If the bowl is not the cause of your leak or you find you have another carburetor leak after replacing the gasket, move on to checking for a stuck float.
Stuck Float
Check near the intake port for a fuel leak. If you find a leak, you could have a stuck float. The float in the carburetor regulates fuel flow into the bowl. It regulates when to start and stop fuel flow into the carburetor bowl.
When the float is stuck, fuel continues to flow into the bowl and then overflows out of the carburetor. You will have to take the carburetor apart to find out the reason your float sticks.
You may be able to clean it or you may have to replace it. You can find steps to clean your carburetor here.
Stuck Float Needle
Check your float needle. The float needle works with the float to keep gas flowing into the carburetor bowl. If the needle sticks, you will need to replace it.
Tapping on the side of the carburetor with a rubber mallet will work a time or two to “unstick” the needle, but eventually, you will have to replace it.
Usually, a carburetor rebuild kit can be purchased to perform the repair. Have your engine model and spec number available when ordering a rebuild kit or replacement carburetor.
This is different than the model and serial number of your zero-turn. You can usually find the engine information on the side of the engine housing.
Cracked or Soft Fuel Filter
Old fuel in the fuel filter can soften your filter causing it to leak at the seams. Replace a leaking fuel filter. If the plastic is soft, be careful removing it from the fuel lines so a piece of plastic does not break off inside the lines.
Install the new inline fuel filter with the arrow on the side of the fuel filter facing the direction of the fuel flow. This means the arrow should be pointed toward the carburetor and away from the fuel tank.
Bad Fuel Pump
Old fuel sitting in your fuel pump can degrade the plastic housing causing the plastic to become soft and develop leaks at the seams. A vacuum fuel pump needs to be replaced when you notice it is leaking.
Failed Seams or Holes
Depending on the age of your zero-turn mower, it may utilize a high-density polyethylene fuel tank. The seams on the tank can fail to cause a fuel leak. When this happens, you should replace your fuel tank.
If you have an older zero turn that uses a metal gas tank, it can rust and develop a rust hole where fuel can begin to leak.
If this is your problem, you can try to find a replacement tank, but may not be able to find one because it is no longer being manufactured. In this case, you can try to patch your tank using a material like JB Weld.
Faulty Fuel Shut-Off Valve
The fuel shut-off valve is located at the bottom of your fuel tank. It can be made of plastic or metal. Both types of valves are prone to leaking and must be replaced if you find it is the cause of your fuel leak.
Old Fuel Lines
Fuel lines can become dry and cracked. This can make them begin to leak. Another place to check for leaks on your fuel lines is where they are attached to components using clamps. The clamps can become loose or they can puncture the hose causing fuel to leak.
Replace any dry or cracked fuel lines. This is also a good time to convert your clamps to a worm gear clamp if your mower came with pinch-style clamps. The worm gear clamps are less likely to cause leaking because they don’t actually pinch your lines.
Bad Gas Cap Seal
Over time the seal in your gas cap can dry out and fail to cause fuel to seep out of the cap area when it is sloshed around the tank while mowing.
You may not notice a wet area around the fuel cap unless you are specifically looking for it. Fuel will evaporate leaving no signs of a wet spot, but you may still be able to smell it in the air in your storage area.
Check for a failed seal on your gas cap by rocking your mower back and forth to splash gas up to the fuel cap area. Watch for wet areas to form around the cap on the outside of the gas tank. If you notice one develop, replace your gas cap with a new one.
Still Experience Problems with Your Zero Turn Mower?
Many different types of problems can develop in a mower. It doesn’t matter what brand you own.
While some mowers are built with stronger materials, bigger filters, better engines, and tougher spindle housings, they are all going to break down and cause issues at some time. Some may just not develop problems as quickly as others.
I put together a guide with common things that go wrong on zero-turns. In this guide, you will find a list of causes and solutions for a mower dying, smoking, vibrating, not starting, having cutting issues, and more.
Check out my guide at Common Zero Turn Mower Problems: How to Fix Them
If you still can’t find the solution to your problem or you don’t feel comfortable troubleshooting or repairing your mower, it is best to have an experienced mechanic check out your mower.
You can visit your local dealership that provides repair support for your brand mower. You may also find a lawn mower repair shop with experienced small engine mechanics.