My Lawn Mower Starts Then Dies (What’s Wrong?)

If you have a lawn, you know how good it feels to have a nicely moved lawn. The smell of that freshly cut grass… aah, feels amazing, isn’t it? A morning at such a place is just what is needed.

Some people just love the entire process of mowing the lawn all by themselves. But the fun is shattered as soon as your machine decides to break in between, and you must struggle to work with it.

This simple work can also turn into a big hassle and seem challenging if the machine starts throwing up.

If your lawnmower starts and then dies immediately, there can be many reasons associated with it. Here, in this article, we will discuss the possible reasons for it and provide you with some suggestions on how you can fix it.

What Can Be The Causes?

Carburetor Problems

If your lawnmower starts, runs briefly, and then dies, it can be due to one or all the following common reasons,

  • A dirty carburetor or a clogged carburetor bowl
  • Defective or dirty spark plugs
  • Old Gasoline
  • There is too much oil in the reservoir.

We will discuss each one of them deeply in the following sections, know why it can result and what can you do to fix it.

Carburetor Problems

This is the most common reason behind a lawnmower starting initially and then dying. It can be due to a lack of proper maintenance.

It is very logical as in winters you do not really use the machine and it sits there all day long.

While in temperate areas, you use it hard all year round. So, problems with carburetors can be quite common.

Let us understand what a carburetor is and what is its role?

What is it about Carburetors?

A carburetor is basically responsible for mixing gasoline with just the correct amount of oxygen to create combustion. A steady flow of gasoline is required for the engine to run smoothly.

Once you start the engine, gasoline flows from the tank through the hose and runs down into the carburetor bowl. Inside the bowl, there is a floater which controls the outflow and inflow of the gases.

As the engine starts, the air is sucked in the air vent and the air pressure is created by the engine, atomizes the gas, and mixes it with the oxygen.

This air-gas mixture is now evenly sprayed in its finest form into the spark plug chamber creating a spark.

The crankshaft thus is rotated continuously by the combustion which is necessary to allow the mower engine to run.

When the carburetor is dirty or clogged the major functions of the carburetor is compromised. So, your engine may start initially but will not run smoothly and eventually after you pull up the cord.

Fixing the Carburetor Problem

Fixing the Carburetor Problem

To fix a dirty carburetor you need to give it a good blowout. You can use an aerosol can of carburetor cleaner for this purpose. It is cheap costing less than $10 and is enough for a month or two.

You can check out this CRC Carb and Choke Cleaner, 12 oz Aerosol Can. This cleaner uses low volatile organic compounds (VOC) formula. It is a fast-acting carburetor and chokes cleaner that dissolves carburetor deposits such as sludge, gum, and varnish.

CRC Carb & Choke Cleaner 03077 – 12 Wt. Oz. Aerosol, High-Performance Cleaner
  • CRC INDUSTRIES- A market leader that offers impeccably designed chemical solutions to maintain, protect and repair different marine, heavy-duty motor...
  • CARB & CHOKE CLEANER- A fast-acting carburetor and choke cleaner that removes sludge, gum, and varnish from carburetors.
  • FORMULA- Our low VOC formula maximizes carburetor efficiency, improves fuel system function, and ensures optimal fuel economy.
  • APPLICATIONS- Ideal for automatic chokes, carburetor components, crankcase breather element, exhaust gas recycling valve (EGR), heat risers, and...

Its Volatile Organic Compounds formula is designed to maximize carburetor performance, improve fuel system performance, and ensures maximum fuel economy.

However, it does have a drawback of not having a straw for targeted spraying. You get this from any local store or online.

How to Use

For carburetor maintenance, all you should do is before starting the mower engine, give a light spray near the intake hole. It is generally present behind the air filter. Just remove the filter, give the spray in the hole, and replace it back.

Unscrew the bowl and clear it with the cleaner. Clean the screw and hole with carburetor cleaner as well. So, it is better to use a spray with directional spraying straw.

Once you start the mower, it is pulled inside the engine and cleans the dirt in your carburetor.

Defective or Dirty Spark Plugs

Defective or Dirty Spark Plugs

Spark plugs are basically responsible for producing the sparks that ignite the fuel mixture in your engine which in turn powers the engine.

Sometimes the spark plugs get damaged, burned out, or damaged due to which carbon builds up inside them producing weakened sparks. This may prevent the engine from starting or run briefly and then quickly die.

Hence, it is important to keep checking them and changing them when required.

If you have a newly installed plug, you should clean it up and wipe out the dirt, carbon deposits, and oil regularly. But if it is degraded you should replace it immediately.

How to Fix

You can easily locate the mower’s spark plug. In a commonly used walk-behind lawnmower, the spark plug is covered with black cable and is present in front of your mower.

mower’s spark plug

Just remove the plug using the right side of the wrench (mentioned in the user manual). If it is not coated heavily coated with buildup you can try cleaning them yourselves. You can use a wire brush and cleaner to clean the spark plugs. If it is just dirty, this will do the job.

Never use a shot-blasting cleaner to clean your spark plugs.

Replacing must be done if you observe heavy carbon coating or deposition in the spark plugs. This is not a challenging task. You easily purchase a new spark plug from local stores costing around $8-$10.

What Should You Do?

Spark plugs should be replaced every couple of years. You can also do it yearly as a part of annual maintenance.

Change the air filter and the oil as well. It may cost you some $20 dollars, but it is worth keeping your mower in perfectly working condition.

If the spark plug is having heavy deposits of carbon, you should immediately replace it.

To remove a spark plug, first unhook the spark wire. Then remove the old plug with a spark plug socket.

It may sound a bit challenging but trust me is not that difficult and you can easily do it by yourself.

Measure the distance between the two electrodes present at the tip of the plug using a spark plug gauge. You can check the specifications of the model mentioned in the manual provided to know the recommended size.

If required, you can use the gauge to adjust the gap by bending the curved electrodes. As you pull the gauge through the gap, it will drag if the gap is correct.

Now install the new plug and attach the plug lead. Make sure not to over-tighten it during installation.

You can take help from the online tutorials if you are just a beginner and stop immediately if think you are not able to do it to prevent any unlikely damage.

Old Gasoline

Gasoline is the fuel required to run your mower. Therefore, both its quality and quantity are very important.

If your mower is just sitting there, inactive for a while now, it can result in the evaporation of the gasoline present in there.

Gas, when left out for a long time in the tank, can form residues due to the evaporation of its volatile components. This leads to the formation of insoluble particulate residues.

These particulate residues can clog the interior parts of the carburetor and restrict the flow of gas. This would result in your mower starting and dying shortly or not starting at all.

How to Fix?

If the gas present inside the tank is less than half full, you can try adding new gas and dilute the impurities. But if it is more than that, it is better to siphon it out and fill it with new fresh gasoline with some fuel stabilizers.

Stabilizers enhance the quality of fuel and prevent the formation of residues while making the gas-efficient for up to two years.

fuel stabilizers

Check out this STA-BIL Storage Fuel Stabilizer. It will keep the fuel fresh for 24 months during storage which means you will not have to drain fuel prior to storage.

STA-BIL Storage Fuel Stabilizer - Guaranteed To Keep Fuel Fresh Fuel Up To Two Years - Effective In...
  • Keeps fuel fresh for up to 24 months during storage
  • Eliminates the need to drain fuel prior to storage
  • Ensures quick, easy starts after storage
  • Prevents gum and varnish build-up

It also ensures a quick, easy start after storage and prevents gum and varnish build-up. They are very inexpensive costing around $4.43 and keeps your machine running smoothly.

Before mixing, check the instruction for the correct ratio of fuel to the stabilizer.

What to Do?

Mix the fuel with the stabilizer in the correct ratio. You can use a stabilizer or whichever brand you prefer. There are expensive options also available like TruFuel.

This will help you be at peace and you will not have to worry about starting your mower or snow blower machine. It helps to get your machine started in the first pull itself.

To purchase the stabilizers, you can either do them online or find them in any local store.

Too Much Oil in the Reservoir

If there is no issue with the spark plug and there is no deposition as well, the problem might be with the oil.

Possibly you must have over-filled the mower tank reservoir while adding fuel into it, especially if you are not handy with this. It can happen sometimes, and it is completely fine.

Too Much Oil in the Reservoir

You can confirm this as an issue if you see white smoke coming out of the engine. It is a sign that the problem is excessive oil.

When you see a lot of smoke coming out, your machine will continue running for a short time after which the excess oil will drown out of the engine and it will die.

What to do?

For starters, confirm the culprit. Tilt the mower and put a heavy object on its handle to hold it up. This will allow the oil to circulate to other parts of the engine.

After an hour, try running the machine again. See if it runs for a good amount of time before stalling. if it does, well the cause was extra input of oil.

How to Fix

Fixing this issue is quite easy. If you have added an excessive amount of oil, you can simply use a siphon or if you use a walk-behind lawnmower, you can tip your mower on its side and drain excess oil from the input hole.

Now, that you know the aftereffects of adding excess oil, you should just slow down while filling up the mower reservoir and avoid overfilling.

If you are new, use a dipstick to fill the tank to the correct level. Also, while releasing the excess fuel measure the amount of oil in the reservoir before removing and then again after to make sure you get it at the right level.

Excess oil is not only the issue that can occur. Not enough oil is another problem. So, after removing the oil check for the level and add extra to get it to the right amount. When you have the adequate amount, start the mower again.

More Serious Problems

Mostly the reason behind your machine starting and dying eventually are the ones discussed above. But if those are not the reasons, the following can be the more serious issues associated with it.

Faulty Choke

This problem needs a more expert observation to be identified. So, if you want your machine to work smoothly identify this problem early to avoid any further damage.

Worn out Carburetor.

Your carburetor can be more than just being dirty. If it is, better to replace it than to waste your money on repairing it.

Gas line Blockage

If the gasoline is not reaching your engine, it will not start. Any kind of blockage will prevent the flow of gas and will require professionals to detect and repair it.


We hope the article was helpful in letting you know the possible causes of the mower starting and dying soon. Keeping a regular maintenance check is the key to keep your machine running smoothly.

Leave a Comment