Why Does My Lawnmower Run For 30 Minutes Before Dying? How To Fix This Problem

Nothing looks better than a freshly mowed lawn so it’s no wonder that so many of us take pride in regularly completing this garden task.

Mowing the lawn can be a relaxing way to spend some time outside but it’s only relaxing if your lawnmower is working correctly and being cooperative.

Why Does My Lawnmower Run for 30 Minutes Before Dying How to Fix This Problem

Lawnmower trouble can make even the most beautiful afternoon in the sun turn into a source of frustration.

This is especially true when there are no obvious problems with your lawnmower.

The last thing you want or need is for your lawnmower to break down and stop working when you’re halfway through perfecting your lawn.

Although it may often seem that your lawnmower has broken down for no reason, this is rarely the case.

If your lawnmower runs for 30 minutes but then dies, there are a few common factors that can do this.

Luckily, many of these problems have an easy fix as long as you know what you’re looking for.

In this article, we will look at the reasons why a lawnmower might run for 30 minutes and then die.

We’ll also offer some fixes that will hopefully get your lawnmower up and running again without the need to buy a new one.

The Possible Reasons Why Your Lawnmower Might Only Run For 30 Minutes Before Dying

There are several reasons why this might be the case and you will probably need to go through a process of elimination to find out the right reason.

We would recommend that you work through these causes and assess each one until you find that seems to be the problem with your lawnmower.

If you’re lucky, it’ll be the first reason on the list!

Malfunctions With The Spark Plug Or Ignition Coil

Lawnmower engines need both a spark plug and ignition coil to start but problems with these can also cause your lawnmower to stop running after around 30 minutes.

If your spark plug doesn’t produce enough of a spark or your ignition coil fails, your lawnmower will fail too.

The reason why these two elements can fail after the lawnmower has started is due to the heat produced by the engine.

As the lawnmower is switched on and begins to run, the engine will warm up.

This heat is also transferred to the numerous parts in and around the engine that helps the lawnmower run.

Both spark plugs and ignition coils are prone to becoming hot and the cycle of being heated and cooled can take their toll on them over time.

When they become heated, both the spark plug and the ignition coil can expand and even a little expansion can be enough to break the connection that you need to start and keep your lawnmower engine running.

The Fuel Delivery Is Blocked

This is one of the more complicated issues that your lawnmower can have.

This is because the fuel delivery system consists of several different components and any one of them can cause issues that will prevent your lawnmower’s motor from getting the fuel supply it needs.

Despite the number of components that can cause problems, it is most commonly the carburetor that is the cause of any fuel delivery issues.

The carburetor itself consists of several different intricate parts that can fail and it can also make resolving carburetor problems complicated if you aren’t technically minded or don’t have the experience of dealing with the carburetor.

The carburetor has a mixture of air and fuel that flows through it and if the balance or supply of these gets affected, it can lead to lawnmower problems.

For example, some debris in the carburetor bowl or a hole on one of the carburetor’s jets getting blocked can easily prevent your lawnmower from working as it should.

Debris can be a major problem in the fuel delivery system and can affect more components than just the carburetor.

Both the fuel filter and tank can accrue debris as time passes and a build-up of debris in either can cause problems. 

As your lawnmower runs, the debris in your filter or tank can get stirred up due to the vibrations of your engine and the bumps on an uneven lawn.

As the debris gets stirred up and bounced around, they can get into all of the wrong places and block the fuel delivery system.

Problems With The Air Supply

When it comes to igniting and starting your lawnmower engine, a supply of air is essential.

Your lawnmower will need a consistent supply of air to keep the lawnmower ticking over so any disruption will cause problems.

Air passes through your lawnmower through the air filter and into the carburetor.

This means that there are several places where the supply can be dusturbed.

These are mainly the air filter and carburetor themselves, as well as the fuel cap.

Blockages in the air filter are pretty self explanatory as this filter serves the purpose of getting air into your lawnmower.

If it’s blocked, this won’t happen and the lack of air could make your engine die.

The carburetor can also cause problems in a couple of different ways.

This part of your lawnmower can both restrict the air flow and allow too much in and both of these situations will cause problems.

There is an air screw in the carburetor that is responsible for allowing the right amount of air into the engine but if this screw is set incorrectly, you will get too much or too little air.

There is also a gasket in the carburetor at the junction where the two halves of the component meet and this is a common cause of air leaks.

We mentioned that the fuel cap can also be the cause of problems with the supply and this is because these have a one-way vent.

This vent allows air to get into the lawnmower while preventing gas fumes from escaping.

After 20 to 30 minutes, the level of fuel in the lawnmower reduces and if air doesn’t get into the lawnmower, a vacuum gets created in the space.

This leads to the gas fumes no longer flowing through the carburetor.

How To Fix Your Lawnmower 

Why Does My Lawnmower Run for 30 Minutes Before Dying? How to Fix This Problem

Now that we know the potential causes of your lawnmower dying after 30 minutes, let’s now look at some of the solutions. 

Replace Your Spark Plug Or Ignition Coil

This is one of the easier fixes, but before you do replace the spark plug, you should check to see if it is cracked or damaged and whether it still sparks.

Remove the spark plug, attach the spark plug boot, and take hold of it with some insulated pliers, before grounding the tip of the plug.

Pull the starter rope (you may need another pair of hands for this) and if it sparks strongly, it doesn’t need replacing.

When you get a new spark plug, try this princess again. If the new plug doesn’t spark, then it will be your ignition coil that is the problem.

This is trickier to replace and you might want to call in an expert.

Clean The Fuel Filter And Carburetor

With some lawnmowers, the fuel filter is connected to the fuel line and is easy to access.

Other lawnmowers have their fuel filter inside the fuel tank, meaning it can’t be easily accessed and it can’t be replaced either.

If you’re not sure where the fuel filter is in your lawnmower, check the manual or with the manufacturer.

If the fuel filter is separate, cleaning or replacing it is a relatively easy process.

Swapping out an old filter for a new one and reattaching the clamps shouldn’t cause you too much trouble and is easier than touching the carburetor.

If replacing the fuel filter doesn’t solve your problems, then you should move onto the carburetor.

You will need to remove and clean this and one of the easiest ways is to use a can of carburetor cleaner.

Some of them have small straws included that allow you to easily direct the cleaner through the carburetor.

Taking apart a carburetor can be a little tricky as they have a lot of parts and elements.

You may want to take photos or notes of how the parts go back together if you’re unsure.

Once the carburetor has been taken apart, you can give it a good clean by soaking it in carb cleaner.

Your final option is to buy a completely new carburetor to replace the old one.

If in doubt, we would recommend getting a professional to look at your carburetor.

This can save a lot of time and headaches if you don’t have the experience to do it yourself. 

Make Sure The Air Supply Flows

The air supply flows through several parts of the lawnmower so this means that you will need to check several different points.

We would recommend that you start with the air filter as this is the most common cause of air flow problems.

You can easily clean air filters and ensure they’re free of any debris, but it’s just as easy to replace them.

Lawnmower filters are generally inexpensive and its best practice to change them every season regardless of problems, anyway. 

If replacing the air filter doesn’t resolve your problems, your next stop should be the fuel cap.

Damaged or blocked fuel caps are another common cause of airflow problems and can often cause your lawnmower to die.

Check that the fuel cap is in good condition and that it has a properly working vent.

The last place to check for air supply problems is the carburetor.

All of the carburetor gaskets should fit well and not be damaged or cracked in any way.

You should also check the air screw and you can normally find this on the bottom of the carburetor.

The setting of the air screw will depend on your lawnmower so you will need to check with the manufacturer to ensure it is right.  

Final Thoughts

In this article, we looked at the reasons and fixes for why your lawnmower might die after 30  minutes.

We hope this article can help you solve your lawnmower problems.

Brian Freis