Sometimes a problem with your lawn mower can be caused by the simplest of things and won’t need you to take out the tool bag and strip the engine in search of the root cause. It could be the gas cap. Adjusting the gas caps will fix your lawnmower in minutes.
The short answer is: Lawn Mower Gas Cap Not Venting Symptoms
Proper venting will keep fuel from leaking from the gas tank. Once enough back pressure has been created, gasoline in your tank will be held back. The mower will not be able to get gas. If the gas cap isn’t properly vented, your mower may splutter, misfire, and stall as if it was running out of gasoline.
Why Will a Mower’s Gas Cap Stop Venting?
A mower’s gas cap will usually stop venting because it’s blocked. This could be due to dirt or grass clippings becoming stuck in the cap. Also, I’ve seen gas caps get damaged and deform the plastic in the cap. Stacking things up on your mower when it’s not in use is an easy way to damage a gas cap.
What’s Actually Going On During Venting
Gas is used to power the lawnmower. The tank’s gas volume drops and is replaced by gas. The gas cap contains a vent which allows air to enter the tank and replace gasoline.
This is similar to drinking water out of a plastic bottle. If you don’t let air back in as you drink, water will stop flowing. The lawn mower will run out of fuel.
How much vacuum is created depends on the fuel level and the size and shape of your gas tank. This is why your lawnmower might stop running or run for only a few minutes before you start to feel the effects.
How to tell if your Lawn Mower Gas Cap Does Not Vent (Telltale Signs).
I’m sure you are all too familiar with how your lawn mower acts when it is running out of gas. Gas cap problems that don’t vent are the same. A clogged gas valve can cause misfiring or spluttering, and eventually, stalling.
Even if you have symptoms, your lawn mower will continue to work normally. It’s not as if there is an ongoing problem with the mower, like having bad gas or a dirty air filter, which create a problem the entire time you’re using the lawn mower.
After the last symptom, the lawnmower will still work for a while. This is because the gas vent usually has enough clearance that the vacuum can be released. Although it might take some time, the gas will usually find its path back into the tank. So, let’s take a look to see how you can test if your fuel cap is blocked.
Take out the gas cap
If you are always out mowing your lawn, this test can be performed. If symptoms occur, turn off your lawnmower. Once you have removed your gas cap, the vacuum will release.
Next, you should top-off your gas tank by changing the cap. If it’s a problem with the gas cap venting, then the mower should work fine again until the vacuum builds up. If this is the case, you can move on with the next test.
Examine the Vent
Gas caps come with a variety of sizes and designs. Gas caps for smaller engines often have tiny holes that allow air to flow in both directions. If yours does, make sure it isn’t blocked.
If yours doesn’t have this design and appears to be more complicated, then you can use a different test. Let’s take a look at the next test and confirm the venting problem.
Check the fuel flow
The final test is to verify that the venting is working and if it creates vacuum. This is where you will need these tools.
Tools Required to Test Gas Cap and Not Venting
- Fuel storage containers
After you have removed the fuel line, you will check the fuel flow from your tank during this test. If you notice a problem with the fuel flowing, it is likely that there have been venting problems. Let’s take a look at the steps you’ll need to follow.
Steps to Test Fuel Flow
First, place a container directly below the outflow to capture the fuel that is leaked. Next, use your pliers and remove the fuel lines and clips.
Now observe the fuel flow from the tank to the container. It should flow in a steady stream between the tank and the container until it is empty. It could be a problem in the venting system if the flow is slow or stops before the tank fills.
You can confirm this by removing your gas cap and monitoring the fuel flow. If the fuel flow doesn’t stop, it’s likely that the problem with the venting is solved.
How to Clean the Lawnmower Gas Cap Vent (Stupid Simple Solutions).
This is, like the title says, a very simple fix. If your gas cap has a breather hole, remove the obstruction. The only thing you need to fix this problem is a pin or a needle. The pin/needle can be used to break through the blockage.
You can use a small drill bit to open the hole if you find that there is plastic damage. A drill bit measuring two to three millimeters in length should suffice.
Whichever method you need to use, just make sure that you don’t make the hole bigger than it needs to be or you will end up needing to replace the cap. It is easier to replace gas caps that have more complicated designs.
Lawn Mower Gas Cap is Not Venting Alternatives
It is worth noting, however, that symptoms of a gas caps that do not vent can be applied in other situations.
Some lawnmowers do not use the gas cap to vent gas tanks. You can still look out for the same symptoms and carry out the same test, but you might find that you don’t have a vented gas cap. This is common with large zero-turn and ride-on lawnmowers, which use vent pipes or valves. The symptoms and the solutions to these problems will vary depending upon which model you choose.