The smell of gas fills the air in your storage area. You’ve narrowed down the smell coming from your SCAG mower, but you can’t find the leak. The good news is that there aren’t too many places on your mower to check for a leak.
The bad news is, fuel evaporates over time and may leave no signs of leaking other than the smell in the air making it a little difficult to find the leak.
A SCAG lawn mower leaking gas will leak from the carburetor due to a bad carburetor gasket, stuck float, or stuck float needle. It may also leak from the fuel filter, fuel lines, fuel shut-off valve, fuel tank seam, fuel pump, or gas cap.
Before working on your lawn mower, make sure you ventilate the area to introduce fresh air. Working around gas fumes can be dangerous.
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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 SCAG Lawn Mower May Be Leaking Gas
It is common for the carburetor on your SCAG mower to begin leaking sometime over its lifespan. The carburetor is the place where a little bit of gas is stored once it leaves the fuel tank.
Old gas that sits in the carburetor can leave behind varnish and gummy deposits that can cause small components to stick in the carburetor allowing gas to run out of the carburetor. The carburetor gasket is another likely place on the carburetor that can begin leaking.
Gasket failure in the carburetor bowl
The first place to look for a leak coming from the carburetor is from the gasket. This is a gasket located between the carburetor bowl and the carburetor that looks a lot like a rubber band. The bowl located on the bottom of the carburetor is where a little fuel is stored.
Gas is prone to leak from the gasket area because of its proximity to the engine. The gasket is subjected to swings in temperature that put stress on the gasket. The gasket gets hot when the engine is running and cools down when it is not.
Due to the extreme temperature change, the gasket can become dry and brittle losing its ability to seal the bowl to the carburetor.
Check for signs of leaking coming from this area. If you do find a leak, you will have to replace the carburetor 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. Lower the bowl to remove it.
Take off the old gasket and replace it with the new gasket. Reinstall the bowl and secure the bowl to the carburetor by tightening the screw.
If you find the leak isn’t coming from the gasket or you repaired the gasket and still have a leak coming from the carburetor, check to see if the carburetor is leaking near the air intake port.
If you find a leak from this area, the culprit is most likely a stuck float. The float is the part that regulates the amount of fuel that is allowed into the carburetor bowl.
When it gets stuck, the float will not be able to stop the amount of gas flowing into the carburetor bowl. It can cause your SCAG mower’s carburetor to overflow and run out of the carburetor.
A leak that is caused by a stuck float must be repaired by disassembling the carburetor and repairing the stuck float. You may be able to clean your SCAG carburetor to free up the float.
You may end up having to rebuild the carburetor using a rebuild kit or replacing it depending on the condition of the carburetor.
Once you get inside your carburetor to look at the float, you may find the float is fine and the float needle is actually stuck. The needle works with the float to keep gas flowing into the bowl. When the needle is stuck, you must rebuild your carburetor.
To temporarily loosen your stuck needle, tap the carburetor with a rubber mallet. A rubber handle on a tool also works well. This may work once or twice, but eventually, you will have to replace the float needle to correctly fix your SCAG carburetor.
Bad Fuel Filter
Old fuel will degrade and soften the plastic housing on the fuel filter. The fuel filter will begin leaking at the seams when this happens. Replace a fuel filter that is leaking due to an old degraded or damaged filter.
Be careful when changing out your filter if the plastic is soft. The filter ends can break off in the fuel line.
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 SCAG’s routine service maintenance.
Changing it regularly will keep you from having a fuel leak due to the filter degrading.
Bad Fuel Pump
Just like the fuel filter can degrade from old gas, the same is true of your fuel pump. Check the seams of your fuel pump for leaks. Replace the fuel pump with a new one when you find a leak.
Fuel Tank Seam
SCAG lawn mower fuel tanks are made with high-density polyethylene material that can begin leaking at the seams. It is best to replace the fuel tank when you find a leak coming from the seam.
Fuel Shut-Off Valve
A SCAG lawn mower has a fuel shut-off valve often times located behind the seat. This valve is used to stop fuel from flowing through the mower. Fuel valves are prone to leak over time. The fuel shut-off valve must be replaced when a leak is found.
Old Fuel Lines
As the fuel lines on your SCAG mower become older, they will dry out, crack and begin leaking. Check the fuel line coming out of your fuel tank and follow it up to your carburetor. Check for leaks coming from cracks in the line and from punctures around the hose clamps.
Replace fuel lines where you find a leak. Pay attention to the diameter of the fuel line so you purchase the correct replacement hose. It is also good practice to replace the lines that dry and develop cracks before they begin to leak.
When replacing your fuel lines, take a look at the clamps. If your mower has pinch-style clamps, I recommend replacing them with worm gear clamps because they are less likely to puncture the fuel line and cause leaking.
Bad Gas Cap
The seal around your SCAG mower’s gas cap can dry out and no longer seal correctly. Fuel can begin leaking around your gas cap when fuel is sloshed inside the fuel tank when operating your mower.
You may not have noticed a leak in this area because gas evaporates and will not leave any sign of leaking. You may only be left with fumes in the air. To check for a bad seal on your gas cap, carefully rock your mower back and forth to splash fuel around the gas cap area.
If you notice a wet area forming around the fuel cap outside of the tank, replace your cap with a new gas cap.
Still Experiencing Problems with Your SCAG Lawn Mower?
Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.
To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your mower.
You can find this guide at Common SCAG Lawn Mower Problems & Solutions.
If you are unsure how to perform diagnostics and repairs on your lawn mower safely, it’s best to have a professional complete the repairs.
This will help you avoid personal injury or additional damage to the mower. Your local SCAG lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.