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Your Craftsman Mower is Leaking Gas: Solved!

Walking into your garage and getting overwhelmed with a smell of gas fumes can be alarming. You look around and identify the fuel smell is coming from your Craftsman lawn mower, but you can’t find the source of the fuel leak because, unlike oil, fuel tends to evaporate and doesn’t leave big stains underneath the leak.

Craftsman lawn mowers may leak gas when components of the carburetor fail or become stuck; the fuel lines, filter, or pump deteriorate; the gas cap doesn’t seal correctly; or the fuel shut-off valve fails.

So, unless your fuel leak is leaving a significant puddle, it can be pretty hard to find the where it is coming from. I have shared a list of items that can cause your Craftsman fuel leak.

Craftsman mower is 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, knowledge or are not in the condition to perform the repair safely.

Reasons Why Your Craftsman Lawn Mower Leaks Gas

Craftsman mower parts that are vulnerable to leaking gas:

  • Carburetor
  • Fuel Pump
  • Fuel Filter
  • Fuel Lines
  • Fuel Tank
  • Fuel Shut-Off Valve
  • Primer Bulb
  • Gas Cap

Craftsman Carburetor is Leaking Gas

Gasket failure in the carburetor bowl
The carburetor bowl is located at the bottom of your carburetor. This is where some fuel is stored and used to keep your engine running after it leaves the gas tank. You will find a rubber band looking gasket between the base of the carburetor and the bowl that could be your problem.

Your lawn mower may be leaking fuel out of the bottom of the carburetor because the gasket failed between the carburetor and bowl. This gasket is prone to becoming dry and brittle because it is located near the engine where it is consistently exposed to hot conditions when the engine is running and cool conditions when it is not. This constant warming and cooling makes the gasket fail to seal.

Replace the rubber gasket when you identify a leak out of this area of the carburetor. It is a pretty simple repair. Begin by shutting off of the fuel to your mower by turning the fuel shut-off valve, if your mower has a valve, or use clamps to stop the fuel flow. Once you have stopped the fuel flow, remove the screw and remove the bowl.

Have a rag on hand to catch any fuel in the bowl. Replace the gasket and reinstall the bowl and the screw. Turn the fuel back on and wipe down the carburetor bowl. Inspect the carburetor to make sure you don’t have any more leaks. If you do find leaks, continue check the carburetor by inspecting the float and needle.

Stuck carburetor float
Check to see if you fuel leak is coming from the air intake port. If you find a leak in this area, most likely it’s the result of a stuck float. The float is the part of the carburetor that regulates how much gas is allowed into the bowl.

If the carburetor float does get stuck, it won’t stop fuel flow and excess gas will begin to run out of the carburetor. If this is what is happening to your carburetor, you will need to take it apart to see what it causing your float to stick. Read procedures on cleaning the carburetor in this article.

Stuck float needle
The float needle works with the float to keep gas flowing to the bowl. Sometimes the needle will get stuck. You can try to “unstick” the needle by hitting the side of the carburetor gently with the handle end of the hammer.

This may work a time or two to get your carburetor working again, but it will continue to happen and your carburetor will need to be rebuilt or replaced.

You can buy a carb rebuild kit and repair it yourself or have your local mower repair shop rebuild your carburetor.

Craftsman Fuel Filter Cracked or Deteriorating Causing a Leak

Because an inline fuel filter is made up of plastic and fuel consistently sits in the fuel filter, the plastic can become soft and begin to leak. A leaking fuel filter needs to be replaced.

Bad Fuel Pump Can Begin Leaking Gas

Most fuel pumps on a Craftsman is made of plastic. Not all mowers use a fuel pump. Your Craftsman will use one if the carburetor sits higher than the fuel tank. The fuel pump will pump fuel up to the carburetor. The plastic can crack, begin seeping at the seams and deteriorate from running old fuel.

Rusted or Failed Seams on Your Craftsman Fuel Tank Will Begin to Leak

Most fuel tanks today are made with a high-density polyethylene. Eventually, the seams on the tanks can fail causing your fuel tank to leak. If you have a much older Craftsman mower, your mower may be using a metal gas tank.

The challenge with metal gas tanks is they can develop a rust hole. You must replace your gas tank if you have a poly tank with a leak in the seam or a metal tank with a rust hole.

Craftsman Fuel Shut-Off Valve is Prone to Leaking Gas

You may or may not have a fuel shut-off valve on the bottom of your fuel tank. This valve does exactly what its name indications. It shuts off the fuel. Whether you have a metal or plastic fuel shut-off valve, both types are prone to leaking.

Old Craftsman Fuel Lines Can Become Dry and Leak

Bad fuel and the weather elements can cause your fuel lines to become dry and cracked. You need to follow the fuel lines out of the fuel tank to check for wet spots. Also, pay close attention to the area near the fuel lines clamps as these can also puncture or weaken the fuel line.

I like to use worm gear style hose clamps instead of the pinched style because they are less prone to causing problems when pinching the lines to prevent fuel leaks. Any cracked fuel hoses must be replaced.

Cracked Primer Bulb Can Begin to Leak Fuel

Some lawn mowers use a primer bulb to prime the carburetor. Pressing on the bulb moves fuel into the carburetor. When the primer bulb becomes overfilled, it can begin leaking. It can also leak when the bulb’s plastic begins to wear and crack. Another place to check for a leak is where the bulb meets the fuel line.

Bad Craftsman Gas Cap Seal Can Cause Leaking

If you’ve gotten to this step and haven’t found it a leak, there is a good chance your gas cap could be the cause of the leak. When gas fumes fill the garage and you can’t find the leak, it is possible the leak is out of your fuel cap. The fuel evaporates before you can find a wet spot on your mower.

The seal around your Craftsman’s fuel cap can fail allowing gas to leak out of the edges of the cap. A good way to check for a bad seal on your cap is to rock your mower back and forth to splash fuel up to the cap and check for signs of a leak around the base of the cap.

If you find the cap isn’t sealing correctly, you must replace it. You can find Craftsman gas caps online or go to your nearest Craftsman servicing center.

Still Having Problems With Your Craftsman Lawn Mower?

It would be nice to own a mower that will never give you problems. However, they don’t exist. Own a lawn mower long enough you bound to run into problems. The most common of them are problems with starting, smoking, dying, vibrating, and cutting.

I put together a handy guide to help you quickly identify items that can cause a problem in your Craftsman along with ways to solve them. You can find this guide at: Common Craftsman Lawn Mower Problems & Solutions.

If you are unsure how to safely perform diagnostics and repairs on your Craftsman lawn mower, 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 Craftsman lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.