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Your Toro Lawn Mower is Leaking Gas: Fixed!

Your Toro lawn mower’s fuel system consists of many components that can fail and begin leaking. Finding a fuel leak can be a little difficult. You can smell the gas, but you can’t find a wet spot anywhere around your mower. This is often because gas will evaporate into the air.

A Toro lawn mower can begin leaking gas because old fuel has deteriorated and degraded your fuel system components. Fuel components can begin leaking when they are dry, cracked, aged, and dirty affecting the carburetor, filter, pump, gas cap and fuel lines.

I have put together a list of items you need to check on your Toro when your mower smells like 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, knowledge or are not in the condition to perform the repair safely.

Reasons Your Toro Mower is Leaking Gas

  • Carburetor is dirty
  • Fuel filter is old or cracked
  • Fuel pump is old or cracked
  • Gas tank is rusted or has a failed seam
  • Fuel shut-off valve not sealing
  • Fuel lines are dry or cracked
  • Primer bulb is cracked
  • Gas cap has a bad seal

Toro Carburetor is Leaking Gas

Once your fuel leaves the gas tank it is temporarily stored in the carburetor. There are several parts on your carburetor that can become gummed up and fail to work properly.

Gasket failure in the carburetor bowl on you Toro Mower

Take a look at the bottom of your carburetor. You will find the carburetor bowl where the gas is stored before it is used to create a combustion in the engine. There is a gasket between the carburetor and the bowl. It looks like a rubber band. The gasket will eventually wear out and cause your Toro mower to begin leaking gas.

The gasket around the carburetor bowl failing is actually a common failure because of its continual exposure to hot and cold temperatures. It sits next to the engine and heats up when the engine get hot and cools down when the engine is off. This temperature change causes the gasket to become dry. It loses its ability to form a good seal between the bowl and the carburetor.

Fix: A bad gasket is an easy repair. First, shut off the fuel supply using your fuel shut-off valve located underneath your fuel tank. If your mower doesn’t have a shut-off valve, use a clamp on your fuel line to stop fuel flow. Second, remove the screw at the bottom of the bowl.

Have a rag ready to collect gas in the bowl and remove the bowl. You need to take the old gasket off the bowl and put a new gasket in place. Lastly, Reinstall the bowl and replace the screw to hold it together.

Stuck float in your Toro mower’s carburetor

Now focus on the area of your carburetor by the air intake port. If you find this area is wet from fuel, you may have a stuck carburetor float. A carburetor float is a part that regulates how much gas is allowed to enter the carburetor bowl. If the float gets stuck and it’s no longer able to gauge the amount of fuel it lets into the bowl, the fuel can continue to flow into the bowl. The excess fuel will run out of the carburetor.

Fix: The carburetor will have to be disassembled to find the reason why your float need is stuck. You may be able to clean the carburetor parts to get your float working or you may have to rebuild it. Find the steps to clean your carburetor in this article.

Stuck float needle on your Toro Mower

Your float needle works in combination with the float to keep gas flowing into your bowl. The needle can stick and will have to be replaced when this happens.

Fix: You can try to “unstick” your float needle by tapping the side of your carburetor gently with a small rubber mallet or the handle end of your hammer. This is only a temporary fix that may only work a time or two. You will have to take your carburetor apart and replace the needle.

Toro Fuel Filter is Cracked or Deteriorating Causing a Leak

Old fuel can collect in your fuel filter and cause your filter to degrade. The plastic becomes soft and begins leaking at the seams. Ethanol is used in most of fuel sold today. Ethanol is corrosive to lawn mower components and can cause problems in the fuel system and engine.

Always use fresh fuel in your Toro mower within 30 days. If you are unable to use it within this time frame, add a fuel additive to stabilize your fuel. Lawn mowers use regular unleaded gasoline with an octane rating of 87 or greater with no more than a 10% ethanol content. Check out my article on the right gas to use in your Toro mower.

Fix: Remove your fuel filter and replace with a new filter. Be careful when removing the ends of the filter from the fuel line. The plastic can get pretty soft and break off inside the fuel hose.

Bad Toro Fuel Pump Can Begin Leaking Gas

Most fuel pumps on a Toro are made of plastic. Just like the plastic in your fuel filter can degrade and become soft, you can have the same problem with your fuel pump. The fuel can cause your pump to leak around the seams and cause damage internally. When this happens, the pump is no longer able to build the pressure it needs to pump fuel.

Fix: Replace your fuel pump when you find the pump is leaking gas. Again, be careful not to break off any soft plastic from the ports off the fuel pump.

Rusted or Failed Seams on Your Toro Fuel Tank Will Begin Leaking Gas

Depending on the age of your Toro mower, you will have a metal or high-density polyethylene gas tank. You will find metal tanks on older lawn mowers. These types of tanks can rust and develop holes causing fuel to leak. You can use a petroleum resistant epoxy to try to seal the hole like TankWeld by J-B Weld. You can also replace the tank if a replacement is still available.

Most Toro fuel tanks today are made with a high-density polyethylene. The seams on the tanks can fail causing your fuel tank to leak. The best solution is replacing your fuel tank.

Toro Fuel Shut-Off Valve is Prone to Leaking Gas

Plastic and metal fuel shut-off valves are known to leak gas. You will find the shut-off valve located under your fuel tank if your mower uses one.

Fix: Replace your shut-off valve if you find it leaking gas

Old Toro Fuel Lines Can Become Dry and Leak

Overtime, your fuel lines will become dry and cracked. Follow the fuel lines from your gas tank checking each section of hose for any wet spots. Pay close attention to sections of the hose that are held on by clamps. The areas by the clamps can compromise your fuel hose.

Fix: Any cracked fuel lines need to be replaced. This may also be a good time to replace the type of 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.

Cracked Primer Bulb Can Begin to Leak Fuel

Your Toro mower may have a primer bulb to prime the carburetor. Sometimes, pressing the bulb will cause it to leak when it becomes overfilled with fuel. It may also leak where the bulb meets the fuel line. A primer bulb is relatively easy to replace if you find any gas leaking.

Bad Toro Gas Cap Seal Can Cause Leaking

If you have checked out everything else on the list and still can’t find why your Toro is leaking gas, it’s time to check you gas cap. You can miss a gas leak around your cap because fuel evaporates and you might not even notice a wet spot.

The seal that sits in your gas cap that forms a seal when your cap is placed on your fuel tank can become dry and no longer seal. In order to check your fuel cap, rock your mower back and forth so it splashes gas up to the cap area. Watch for wet spots forming around the cap.

Fix: Replace your Toro gas cap if you see wet fuel spots forming around your cap.