Lawn Mower Won’t Stay Running – What to Do?

The aroma of freshly cut grass is unbeatable. However, it’s inconvenient to be all set to mow your lawn just to have your mower startup, and you find the lawn mower won’t stay on to cut your grass.

It may feel as though you’re alone when your lawn mower starts and then dies, but the issue is more common than you would think.

The sound of a sputtering lawnmower isn’t fun, but fortunately, the solution is much simpler than you would think. In our guide, you can learn why my lawn mower won’ t stay running and what you need to do to fix it.

red mower

By the end, you’ll be able to identify the issue and fix it, even if it means getting the tools out to clean your carburetor or change a part such as the fuel filter. (Find the Best Electric Lawn Mower)

Why Does My Lawn Mower Only Run For a Few Seconds Then Dies?

If your lawn mower starts and then dies after a few moments, there are a few reasons for this happening. Reasons are common, and they comprise a dirty carburetor, a faulty spark plug, lack of gas to the engine or a clogged air filter.

To fix most of these is an easy job and can be done as part of your annual lawn mowing machine maintenance.

  • The most obvious choice is the carburetor, and every gas-powered engine has a carburetor. It is the function of this device to mix gas and air for the piston to burn.
  • As you start your engine, gasoline will flow from your gas tank into the carburetor bowl. When it reaches here, there is a float to control the flowing of gas.
  • As your mower’s engine starts, the air gets sucked in through the air filter, and the engine creates air pressure to mix with the gas.
  • The air-gas mix is sprayed into the spark plug chamber, where it meets the spark plug’s spark.
  • With a steady flow of gas and air, you should have combustion, and your mower will keep running.

Regular mower maintenance can stop these issues and keep your mower running longer and powering through cutting your grass. Do this, and you can save yourself a costly repair.

Why Does My Lawn Mower Start But Not Stay Running?

Your mower won’t start and keep running can be from something as simple as old gas in your tank. If you haven’t used your mower since the previous season and you have last season’s gas in your mower tank, then drain the fuel tank and fill it with fresh gas.

You may need to clean or replace your fuel filter as first can accumulate in old gas from the bottom of your tank. (Find the Best Riding Lawn Mower)

Another common reason you find mowers not running is that the air filter is dirty and blocked. This is truer if you haven’t used your mower in a while and it has got dirty. Any dust can stop the air flow, and most times, replacing the air filter is better than trying to clean your air filter.

How Do You Fix a Lawn Mower That Won’t Stay Running?

Before looking at the primary culprit for a push mower wont stay running, here are how to deal with other solutions when your mower stalls.

Air and Spark

We’ve seen how an old air filter can cause a dirty air filter. If your air filter is clogged, the engine won’t get enough air to burn.

The air filter will be easy to locate depending on your mower. All you need to do is to remove this and undo any fastening holding in your filter. You will see dirty filters coated in carbon deposits or oil. A new filter is cheap and easy to locate.

Dirty spark plugs lead to inferior combustion. It is possible to take an emery board or fine grit paper to clean dirty plug electrodes.

You may find it a better solution to replace the plug rather than try to clean it. If the plug has a large gap, you can find it fires on and off, so this can be a reason your mower keeps stalling.

Once you rule out the issues of dirty air filters, old gas or a worn spark plug, you are left with direct fuel problems.

If fuel sits in the mower, it causes the issues we have seen and more. Gas could have partially evaporated, thus leaving a varnish-like residue blocking your carburetor inlets and outlet ports.

Besides this, fuel may have absorbed water, which condensed inside the gas tank. Draining the tank alone won’t fix the issue, so here is what you need to do. In either case, you’ll have to drain the gas tank and your carburetor. Before doing this, you need to clean the carburetor and replace the fuel filter. (Read Best Time to Fertilize Lawn Before or After Rain)

How Do You Fix Lawn Mower That Starts Then Dies?

Loose & Dirty Carburetor

A loose carb won’t let your engine function as it will create insufficient flow and atomization of gas. Check your carburetor is secure before proceeding.

To be sure all parts work on your carburetor, cleaning the carburetor with carburetor cleaner is the first step since the build-up of gunk is a reason for your mower to start and stop.

spark plug

Dirty or Defective Spark Plug

Even if you have a new spark plug, check it anyway, as carbon build-up can weaken the spark or stop it from sparking altogether.

You’ll just need to clean it up and wipe the covered electrode of carbon deposits and oil. It is worth changing these as part of your regular maintenance. Also, check the plug wire as these can crack and break over time.

Clogged Carburetor Bowl

Most carbs have a carburetor bowl beneath them. You’ll find a screw in the bottom of the bowl and a hole that supports the bowl. If the hole in this screw is clogged, air can’t pass from under the carburetor and won’t regulate the movement of gas.

Remove your bowl screw using a 1/2-inch plug wrench, then clean the dirt out of the bowl. At the same time, clean the dirt in the hole using a thin wire. Spray in the hole with carburetor cleaner. Your fuel system is the key to an effective running mower.

Blocked Gas Caps

Some gas caps have holes in them to help stabilize air pressure.

When this gas cap vent is blocked, it creates a vacuum in the tank where there can be a disruption of gas flowing toward your carburetor. Clean any hole in the cap with a thin wire or replace it with a new one if the cap is already beaten up. (Find the Best Mulching Lawn Mower)

Too Much Oil

One thing that can crop up is when you have done the above; you have an overfilled oil reservoir. You can spot this if your mower smokes. You can drain this or let it burn off through use.

Lawn Mower Won't Stay Running - What to Do (1)

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