You might not be able to find the exact place on your lawn tractor where it is leaking gas, but you’re sure it’s leaking. The strong odor lingering around your tractor is a good indication. It may be difficult to find where the leak is coming from because gas will evaporate leaving no trace of a wet spot.
A lawn tractor can begin leaking gas from the fuel filter, fuel lines, fuel pump, fuel tank, fuel shut-off valve, or a bad fuel cap. It can also begin leaking at the carburetor due to a failed gasket or stuck float.
Before working on your lawn tractor, make sure you are in a well-ventilated area and are getting plenty of fresh air. Follow all safety precautions outlined in your lawn tractor operator’s manual.
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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.
This is Where Your Lawn Tractor is Leaking Gas
Carburetor is Leaking Gas
If you are experiencing a leak on your lawn tractor, you need to check your carburetor. The carburetor is subject to leaking over time. The carburetor is the first place a little fuel is stored after it leaves the fuel tank.
Gas that ages and sits in the carburetor can leave gummy deposits that cause components inside your carburetor to become stuck and stop working correctly causing a leak. Another area of your carburetor that is known to dry out and not seal is the carburetor bowl gasket.
Gasket failure in the carburetor bowl
There is a gasket that looks like a rubber band located between the bowl at the bottom of your carburetor and the carburetor. The location of the gasket on the lawn tractor causes it to get stressed and become dry and brittle.
Because the carburetor is located next to the engine, it constantly gets hot while the engine runs and cool when the engine is off. This change in temperature causes the gasket to lose its sealing capabilities over time.
If you notice fuel is leaking around the bowl, you must replace the gasket. To get to the gasket, first clean around the outside of your carburetor to remove dirt.
Remove the screw at the bottom of the carburetor bowl. Have a rag ready to collect any gas remaining in the bowl and remove the bowl.
Take off the old gasket and replace it with the new gasket. Reinstall the bowl and tighten the screw to secure the bowl to the carburetor.
Stuck float in the carburetor
The leak from your carburetor may be coming from the area near your air intake port. If you notice a leak in this area, you must check for a stuck carburetor float. When the float operates correctly, it regulates the amount of fuel allowed into the carburetor bowl.
When the float gets stuck on your lawn tractor, it is unable to control when fuel is to stop flowing into the bowl causing fuel to overflow and leak out of the carburetor. A leak caused by a stuck float must be fixed by disassembling your carburetor to find and repair the cause of the stuck float.
You may be able to clean your lawn tractor carburetor to “unstick” the float or you may have to rebuild or replace it. You can find steps to clean your carburetor here.
Stuck float needle
Once you get inside your carburetor to look at the float, you may find the float is fine and the float needle is stuck. The needle works with the float to keep gas flowing into the bow.
When your needle is stuck, you must rebuild your carburetor. You can purchase a rebuild kit from your tractor or engine dealership.
To temporarily loosen your stuck needle, tap the carburetor with a rubber mallet or the rubber end of a hammer. This may work once or twice. You will have to replace the float needle to correctly fix your lawn tractor carburetor.
Fuel Filter is Cracked or Deteriorating
The fuel leak on your lawn tractor can come from a fuel filter that is cracked or leaking at the seams. Old gas sitting in your fuel filter can degrade the plastic filter causing it to become weak and soft. Learn more about the effects of old gasoline here.
Replace your fuel filter if it is found to be the cause of your leak. Be careful when your plastic is soft. The filter ends can break off in the hose.
Because your fuel filter is necessary to keep dirt from entering your fuel system and engine, it’s important to regularly replace your filter annually when completing your annual lawn tractor maintenance.
Just like fuel can degrade your fuel filter, the same is true of your fuel pump. Check the seams of your pump for leaks. Replace the fuel pump with a new one when it is leaking.
Fuel tanks can fail and cause fuel to leak out of them. Depending on the age of your lawn tractor, you could have a metal or high-density polyethylene fuel tank.
Older fuel tanks are made of metal. Metal tanks can begin to rust and weaken leaving the tank with a hole. The best solution for a hole in a metal fuel tank is to replace the tank with a new one.
Depending on the age of your tractor, you may not be able to find a replacement tank. If that is the case, the next best option is to repair a fuel tank using a product like JB Weld.
New model lawn tractors use a high-density polyethylene material that can fail and leak at the seams. When this happens, it is best to replace your fuel tank when it develops a leak at the seam or it has been damaged.
Fuel Shut-Off Valve
You will find a fuel shut-off valve on the bottom of your fuel tank. It is common for these valves to develop leaks over time. The valve must be replaced to stop the leaking.
Old Fuel Lines
It is normal for your fuel lines to become dry and start to crack as they age. They will begin leaking fuel at the cracks or from punctures caused by the clamps used on the fuel lines.
Cracked fuel lines must be replaced with new lines if you find them leaking or, better yet, before they start leaking.
When changing out your fuel lines, I recommend replacing pinch-style clamps if your lawn tractor uses them. These types of clamps are more likely to puncture your fuel lines and cause leaking.
I like using a worm gear clamp because they are less likely to pinch your lines and cause leaking.
Bad Fuel Cap
If you have checked every item in the list and still can’t find the leak, the problem could lie in the fuel cap. The fuel cap uses a seal to keep fuel from leaking out of the tank where the fuel cap is placed.
When mowing with your lawn tractor, the tractor can bounce while mowing over uneven terrain.
Fuel can splash in the fuel cap area and leak out of the cap when the seal doesn’t work right. If it has been a while since you last used your lawn tractor, you might not see a wet spot formed around the fuel cap because fuel evaporates only to leave you with the smell of fumes in the air.
When the seal becomes damaged or dry in the cap, its fuel cap must be replaced. To determine whether your fuel cap seal is no good, rock your garden tractor back and forth to splash fuel up to the fuel cap.
Watch for a wet spot to form around the cap on the outside of the fuel tank to indicate a bad seal in the cap.
Still Having Problems with Your Lawn Tractor?
You can encounter many different types of problems with your tractor as it ages. I have put together a guide to help you quickly identify the causes and solutions for the type of problem you are encountering.
I cover common problems like a lawn tractor not starting, smoking, cutting unevenly, vibrating, dying after running, and more.
Check out my guide: Common Lawn Tractor Problems & Solutions.
If you encounter a problem you don’t feel comfortable troubleshooting or repairing, contact your local lawn tractor dealership or repair shop for assistance.