Lawn Mower Starts then Dies: 7 Problems with Possible Fixes

Torque wrench, mower repair

Nothing is more beautiful to the eye than the ‘green, green grass of home’.

A beautiful lawn doesn’t happen overnight but, with the constant journeywork of the weed-killing machine, the ‘Lawn Mower’, eventually every blade of grass may be fixed by its influence and design.

Of course, things go wrong from time to time and then apart from the immediate panic, there’s anger, annoyance, and despair. Read on and all of that will go away.

You need to keep your lawn mower working, so this article is designed to do just that. You’ll likely be able to diagnose the problem and then become your own mechanic and fix the faulty lawn mower. You’ll save money and time and feel good about yourself.

7 Possible Causes for your Lawn Mower to Die 

1.      Dirty Carburettor.

2.     Old Stock Gas On Your Lawn Mower.

3.     Defective Spark Plugs.

4.     Too Much Oil In The Oil Reservoir.

5.     Moisture In The Gas Tank.

6.     Faulty Choke.

7.     Faulty Fuel Cap. 

lawnmower having problem

It’s very common for a Lawn Mower to stop running for some reason.  It has fast-moving parts that work together for the mower to function.

Let’s look at the most common reasons and how to fix them. The possible causes and essential solutions of a Lawn Mower that starts but then dies.

1.      Dirty Carburettor 

A Lawn Mower engine has a component called a carburettor which is responsible for providing a mixture of fuel and air to the engine.

This combustion is what will power the blades and supply the engine by continually rotating the crankshaft which is vital to run the mower’s engine.

When the carburettor is dirty, loose, or clogged, it won’t be able to maintain the proper functioning of a steady supply of gas for the engine.

It may start up but won’t run properly and may die shortly thereafter.

The carburettor is in control of mixing gas with just the right amount of oxygen to create combustion.

How To Fix a Dirty Carburettor 

Be sure to always check the carburettor. To avoid the above dirt, spray it with a carburettor cleaner which is designed for this job. Check well if the carburettor is adjusted firmly so that it will be able to maintain sufficient gas flow.

Hence, being unused for a long time can lead to it not starting immediately or, it might start but not run smoothly due to a build-up of dirt. The liquids inside might harden and cause blockage in some parts.

But sometimes all it needs is just regularly cleaning or servicing.

Here are some signs you will easily recognize when your “Carburettor” needs to be fixed.

The Engine Is Weaker On Performance. You will notice that your Lawn Mower cannot cut any more evenly or has a hard time cutting denser grasses. Your carburettor is in bad shape, and you must attend to it immediately.

The Emission With Black Smoke. This is a sign that the carburettor is consuming unusually high amounts of fuel.  You might end up with it consuming more gasoline.

Take extra care because you will be exposed to black smoke that could lead to respiratory and dermatological problems for you.

Your Lawn Mower Starts Then Dies. Suddenly, it shuts down. This is already a sign that your Lawn Mower Carburettor, either way, needs cleaning or fixing.

Jumpy To Start. It is started via a push-button or pulling a cord. A Lawn Mower that has a hard time starting, is a sign that the internal parts are not at their optimum status.

Therefore, now you already know how to spot a faulty Carburettor. Let’s learn whether you should remove it from the Lawn Mower or not.

Try to assess your technical know-how, if you are a mechanic then removing the carburettor and putting it back would be easy. If in case you are not, you are just a casual lawn mower owner, better keep it intact and clean it from there.

How To Clean Your “Carburettor”?

Start With An Initial Check-Up.

Look at everything to assess how you will proceed with the cleaning. You can see exposed wires if there are any. You should be checking first on everything before you do anything.

Remove The Air Filter And Replace It.

The Cheaper Solution is:

All the air that has been sucked inside goes through the air filter.  You could use a damp rag for minimal dirt but use the blow function of your vacuum to remove the dirt.

However, the air filter of your Lawn Mower can be removed, So, it is better to remove it and clean it on its own. You can clean both sides but don’t get it wet as it’s made from paper.

The Best, But Slightly More Expensive Solution is:

Replace it with a brand-new air filter.

Either way, liquids inside may harden and cause blockage in some parts. The grease as well might get gunky and cause the moving parts to be stuck

Red tools and black toolbox

Removal Of All The Dirt And Deposits Manually.

After all, the blowing off the dust with the air-compressor gun and spraying the aerosol cleaner, it is now the time to use your hands and manually remove and clean the leftover dirt.

Be sure to use a damp rag to easily wipe off any solid dirt. When everything is done, be sure to check everything.

Removal Of All Dirt With An Air-Compressor Gun.

After all, you have used your Lawn Mower, there could be a build-up of dirt and filth inside and outside the carburettor.

Some dirt builds up internally in hard-to-reach areas so instead of using your hands to get in there, why not use an air-compressor gun?

You can now easily dislodge any debris in your Lawn Mower.

Spray The Inside With An Aerosol Cleaner.

Do not use water in cleaning your carburettor. It will ruin the machine for good.

The Aerosol cleaner is machine-friendly that sticks to the surface for longer protection. This kind of cleaner has a powerful solvent formula to break down carbon contaminants which are good for cleaning your carburettor.

This time, it requires turning on the machine because it is necessary for the cleaner to go through the machine for the internal parts to be cleaned. Read the instructions carefully.

You can do this to ensure the maximum coverage of your Lawn Mower.

Old, Worn-Out Carburettor.

This could also make your Lawn Mower start then stop and should be replaced immediately. Seemingly your lawnmower has been cutting your grass lawn for a lot of years.

It has not undergone any major service or an overhaul. The carburettor has a lot of moving parts and it is now time to replace it considering the number of years in service.

How To Fix Old, Worn-Out Carburettor

Nevertheless, if you must replace your carburettor, you must be comfortable with dismantling and replacing it.

Some experts would not recommend you buy a carburettor, especially if you have an old Lawn Mower (10 years or older).

It’s preferable that you take this to a bona fide lawn motor mechanic to have the problem resolved.

2.     Old Stock Gas On Your Lawn Mower.

We all know that a Lawn Mower cannot run without gasoline, however, the quality of gas should be equally important.

Gasoline usually turns bad after 30 days. When the gas is stored in your mower and has been left out for a while, the volatile components of the gasoline evaporate leaving behind a greasy residue.

The greasy residue tends to block the gas line and some parts of the Lawn Mower that keeps in control the gas flow that caused your Lawn Mower to stop running.

The Liquids inside might harden which causes blockage in some parts. The grease as well might get filthy and cause the moving parts to be stuck.

How To Fix Old Stock Gas On Your Lawn Mower.

Drain the gasoline completely from the gas tank. You could also try running the engine to clear out as much gasoline from the carburettor as possible.

Afterward, you have it completely clear of gasoline. Put in fresh gasoline along with the fuel stabilizer.

A fuel stabilizer is good because it can prevent residue formation for a long period.

Use A Fuel Stabilizer.

You need to fix the problem by using a fuel stabilizer.  Using a fuel stabilizer is a lot cheaper than a new carburettor. It is mixed with the gas it will stop gumming and keep the gas fresh for up to 2 years.

A Fuel Stabilizer is affordable and inexpensive, an excellent expenditure to enhance the longevity of your mower. Just be sure that you get the fuel to stabilize proportionately right as directed in the owner’s manual of your Lawn Mower.

Another alternative, you could add fresh gasoline to the existing fuel to dilute the impurities of the remaining residue. If ever the old gasoline is more than half of a tank, it would be best to siphon it out and fill the tank with fresh gasoline.

Lastly, change the petrol filter and this will give the carburettor a consistent supply of gasoline.

3.     Defective Spark Plugs

Spark plugs are an essential component of the Lawn Mower’s ignition system. It supplies the “spark” that ignites the air & fuel mixture in your engine.

It is a part that fits on the cylinder head of an internal combustion engine that has two electrodes separated by an air gap which the current from the ignition system of the machine discharges to form the spark to combust the air and fuel mixture.

faulty spark plug

The small explosion makes your engine produce power. If ever they are defective, basically they will not spark, and your Lawn Mower will not start, or may start and then quickly die.

Thus, an old spark plug still exists on your lawn Mower that seems to be heavily degraded with carbon build up, it needs to be replaced or can be cleaned and get it running.

How To Fix Defective Spark Plugs

Check and Inspect the spark plug for signs of wear or damage. Whenever the porcelain insulator is cracked, then an electrode is burned away or damaged. There is heavy carbon build-up at the electrode, and it is necessary to replace the spark plug.

To determine if the spark plug is defective, use a spark plug tester. There will be a strong spark between the tester’s terminals when the engine is cranking. Since there is no spark, it indicates that the spark plug is defective and must be replaced.

An old spark plug with a heavy carbon build-up needs to be replaced which causes the Lawn Mower to not run. To replace it is easy and inexpensive; all you need is the right size that fits well to your Lawn Mower.

Basically, the spark plug on your Lawn Mower needs to be changed every season. You only must manage a lawn care maintenance routine including the gasoline and air filters.

Proper handling of your Lawn Mower would enable the engine to work for a long period without giving you many problems.

How To Replace Defective Spark Plugs

You need the old plug with the proper sized socket wrench. Seemingly the new plug should adjust the gap towards the two electrodes at the top base. There is a recommended size to follow as per the Lawn Mower’s manual.

After that, you can now install the new spark plug and attach the lead.  Be sure to tighten it up enough and stop as soon as you feel some resistance.

4.     Too Much Oil In The Oil Reservoir.

This is another common reason why a Lawn Mower starts then dies – it is by putting too much oil in the crankcase.

Then you should start to run your Lawn Mower and there’s a white smoke coming from the engine. This is also a possible cause for your Lawn Mower to stop running.

When the oil has been overfilled. The excess oil will be burning which produces the blue smoke that caused the engine to start but with much less power.

How To Fix Too Much Oil In The Oil Reservoir

Before starting the engine of the lawnmower, first, check the oil level to avoid overfilling the same with oil. Pull out the dipstick and this will show the oil level.

5.     Moisture In The Gas Tank

In many ways, moisture can get into the gas tank. There are occasions that lead to leaks in the tank, crack in the fuel cap, loose fuel cap, or gas refilling caused by rain.

Basically, gas with moisture can cause your Lawn Mower to start then die right away. The main cause of this issue is the disruption of the air-fuel ratio due to moisture that creates an imbalance in the burning of fuel.

Another issue or problem with moisture in the tank is the water goes to the fuel line since water is heavier than gasoline.

This can freeze up with extreme cold and can damage the fuel system.

How To Fix Moisture In The Gas Tank

Whenever you detect moisture in the fuel line, the best thing you can do is to drain out the gas fully and put in new gas. But check first for the leakage.

You must check the hose that carries the fuel to the engine to see if it fits tightly. Further, you must replace the hose if it’s worn out or loose.

Try to Inspect the rest of the fuel tank including the fuel cap for cracks.  If there is, then remove the fuel cap.

6.     Faulty Choke

A Lawn Mower engine has its choke features. Its function is to allow you to adjust the intake of gas into the air-fuel mixture while reducing the intake of air to create a temporary richer mixture.

The use of choke is usually during the cold weather or when the engine gets cold. In such a way, your Lawn Mower keeps on dying after you choke the engine, most likely there is a problem.

Either the filter assembly or the throttle linkage of the choke system is not functioning.

How To Fix a Faulty Choke

However, if you’re not sure enough in checking the choke system or the linkages, and the problem persists, it is better to take your machine to a repair shop. They will refine the choke or adjust it or may replace some parts if necessary.

7.     Faulty Fuel Cap

This is also one of the causes that seems like the last you would think of or look for. So, if you notice that your lawn mower is consuming too much fuel then check the fuel cap to see if it’s properly closed.

If your lawnmower starts, runs for a while and then dies, you might have a faulty fuel cap.

Most Lawn Mowers have a vented fuel cap. This vent is a check valve that allows air into the fuel tank but keeps gas fumes inside.

You may check the cause of why the gas is streaming out through your fuel cap. It might be the condition of the cap itself. Over a long period of time it could have built-up dirt and grime in and around the vent.

Take notice if there is gas still trapped in the fuel tank, because then, your vented cap is not working correctly, and something is wrong.

How To Fix a Faulty Fuel Cap

Cleaning and testing will be the best way to see if a dirty gas cap is at fault. Anyway, it is so easy to clean a fuel cap.

Just let the fuel cap soak in the soapy water that contain the cleaner mixture for a while. After the cap is cleaned and dried, you can put it back on your Lawn Mower.

Now that we have learned a lot about your Lawn Mower’s critical problems of start then stop, hopefully, you will know what to do once your machine dies after a few seconds of starting.

You are provided with the best information on how to do it and how it works.

Enjoy mowing your lush green lawn.

Types of Lawn Mowers:

Traditional (push-reel lawnmower). This type does not use an engine but rather relies on the kinetic energy provided by the turning wheels.

There is a set of 5 to 8 blades that work together to provide a basic cut. You cannot expect fast or precision cutting with this type.

Walk-behind the Lawn Mower. This type is the most popular due to its efficiency. You can push the lawnmower towards the uncut grass, and everything is cut nicely and evenly afterwards.

lawnmower cutting grass

With this type, the blades are located at the bottom which is powered by a small 2 stroke engine that uses a carburettor.

Ride-on-Lawn Mower.  This type is operated similarly to a car or a golf cart. You sit on the machine and steer it instead of pushing it.

This machine is usually used on stadiums and large green fields which requires faster cutting.

Final Thoughts on Lawn Mower Starts then Dies: 7 Problems with Possible Fixes

When something goes wrong with your Lawn Mower that starts and then dies. You ask yourself, what’s happening? It doesn’t seem right that your Lawn Mower starts but then dies within one minute or seconds.

There could be possibly something wrong.  What’s the problem and how to fix it?  Let’s find out the causes and how to address all these essential problems.

The lawnmower is also known as a mower and grass cutter. It is a machine with revolving blades to cut grass to an even height. Basically, the cut grass height might be fixed by the design of the mower.

It is a kind of machine that is versatile and adaptable to the operator by a single master lever of nut and bolt on each of the machine’s wheels.

The Lawn Mower blades are driven and fueled by manual force, with wheels mechanically connected to the cutting blades.

We think the information given above is sufficient to stop all lawn mower owners from worrying. After all, it’s not rocket science and if all else fails you can always call in the local repairman.

However, we think the above information has given you a newly found independence and freedom you didn’t have before. We hope it’s as enjoyable as it is useful. Happy days! 

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Patricia Godwin

Patricia has many years of experience as a content writer on various subjects, but her first love is gardening. She’s never met a plant she didn’t like and, consequently, she writes about every type of plant you can think of. Once an avid gardener with a herb garden, a succulent rockery, and a rose garden – to mention a few. Nowadays, she’s constantly on the move searching for interesting plants to bring to your attention; and explain to you all the details you need to grow, care and maintain these plants.