Lawn Mower Gas Cap Leaking -What To Do? Best Tips 2023

An annoying gasoline smell around the tank informs about the lawn mower gas cap leaking. It is hazardous for the rider and consumes more fuel than the projected rate. A gas cap on the fuel tank is a reliable seal to prevent dust and debris.

The cap also plays a substantial role in the machinery’s evaporative emission system. Over each time during refueling to the vehicle, the gas cap wears out. Notifying symptoms and avoiding potential issues require a bit of management skill.

Problems Causing Lawn Mower Gas Cap Leaking

If your lawn mower is leaking gas then here are the details about the top 4 problems causing the gas leak is written below:

Worn Carburetor Bowl Gasket

if you are getting a gasoline smell around your lawn mower, most probably it is leaking out of the carburetor as it is worn out the carburetor bowl gasket.

Defective Float Assembly

The gas cap contains various float assemblies in its configuration. Defects in any of the float assembly can cause problems like gas leaking. Here, a float needle or float valve or even the float itself can become defective to leak gas.

Also, see more about toro-timemaster-vs-turfmaster

Leaking Fuel Line

it does not relate this problem to the lawn mower gas cap leaking, but the consequences are the same.

Brittle Primer Bulb

The primer bulb draws fuel through the carburetor when pushed to prime the engine when starting over for the first time. Over a longer period, this rubber bulb gets cracked or brittled and causes the bulb to leak gas.

 Symptoms of a Bad Gas Cap

A bad gas cap cannot perform its purposes like preventing dirt, debris, and dust from entering the gas tank. Symptoms of a bad gas cap alert the owner of a potential issue. Several symptoms of gas cap wear out are noticeable and a few of them are described below:

Fuel Smell From the Vehicle

One of the most common symptoms of an issue with the gas cap that leaks fuel smell around the vehicle. A bad gas cap or a damaged gas cap allows the fuel vapor from the gas tank to leak from the filler neck. Gasoline odor from the motor is a hazardous element for the rider and environment as well.

Cap Does not Tighten Properly

Another symptom of a damaged gas cap is the cap does not tighten properly. The gas caps click a sound once it seals the air with the filler neck. If the click sound is missing and it becomes loose even after a click, then that gas leaks fuel vapor and we need to replace it.

Fuel Cap Venting Test

We can run a test if you are not sure about the symptoms or just say, “I need proofs to proceed further”. Fuel cap venting test will simply identify the air gas on the filler neck of a lawn mower.

The fuel cap venting test allows you to understand if the fuel cap of your lawn mower works perfectly or not. If the fuel cap is not venting properly, then the engines might sputter or might not work at all.

Seal the Fuel Cap Tightly

Unleash the fuel wire and use a container to reserve the fuel until the fuel tank is empty.

Results and Discussions

Inspect if the tank is empty or not. If it is totally empty, the fuel flow gradually becomes slower than the gas cap is venting properly. If you find a good amount of fuel left in the tank, then that means the gas cap is not venting properly and you need to contact your dealer for a new cap.

The Solution to Lawn Mower Gas Cap Leaking

Identifying a gas cap leak is quite easy. As you can smell the gasoline wafting from the fuel filter, that means either the gas cap is cracked or somehow the rubber gasket within it is broken because of excess pressure.

Several repair attempts and swapping a few caps might not solve the problem once and for all. But you can follow the steps written below to avoid lawn mower gas cap leaking:

Change the Entire Cap with Factory Original Assemble

Changing the entire cap with a factory original assembly. This should instantly solve your problem. Before putting a new factory original assembly, be careful about placing the cap as sometimes wrong placement and extra force spoils the air seal.

Insert New Rubber Gasket

Inspect the rubber gasket of the mower’s gas cap. This gasket makes the gas tank air sealed and displacement or corroded gasket leaks the gas. Inserting a new rubber gasket will ensure the air-tight seal on the filler neck and prevent dust debris from entering the fuel tank and maintaining proper venting.

Zip-Lock Bag

As a temporary solution, you can put a zip-lock bag on the neck of the tank covering the gas cap. This will hold the gas inside the bag for now. But one has to remove it after mowing. Though it will block the breather hole in the cap to allow air into the tank.

Note. We do not recommend the zip-lock bag as it blocks the venting process after a while.


Why is gas leaking from my gas cap?

There could be several reasons for gas leaking from the gas cap. Some possible explanations include a damaged or faulty gas cap, a clogged or blocked vent hose, a damaged fuel tank, or overfilling the gas tank. It is essential to address the issue promptly to prevent any safety hazards or damage to the vehicle.

How do you fix a gas cap seal?

To fix a gas cap seal, try cleaning the seal and the cap with soap and water to remove any dirt or debris that may be causing the seal not to function correctly. If the seal is damaged or worn, you may need to replace the gas cap or the seal itself.

In some cases, applying a small amount of petroleum jelly to the seal can help improve its effectiveness. It’s essential to have a properly functioning gas cap seal to prevent gas leaks and maintain fuel efficiency.

Why do lawn mower gas caps have holes?

Lawn mower gas caps have holes to allow air to flow into the tank as fuel is used. This prevents a vacuum from forming inside the tank, which could prevent power from flowing to the engine. It also helps to regulate pressure inside the tank and prevent excess pressure buildup.


Gas caps emit hazardous elements and fuel vapor into the atmosphere. It even causes an annoying gas smell to a more serious engine leak in a lawn mower.

Replacing the old gas cap with a new OEM cap matching with the mower tank model solves a lawn mower gas cap leaking, and it is the easiest ideal solution available on any household level.

Leave a Comment