My Lawn Mower Starts Then Dies: What’s Wrong?

My Lawn Mower Starts Then Dies What’s Wrong

When it comes to maintaining your lawn, a lawn mower is an invaluable resource. Some gardeners love the smell of freshly cut grass, however, cutting a slightly overgrown lawn can become rather problematic if you have a lawnmower that does not seem to be cooperating.

Does it start and then die shortly after? This is a common problem and there are several reasons why it may be happening. Essentially, it is your lawn mower’s way of communicating that there is a deeper problem. 

In our guide below, we have identified what may be causing your lawnmower to start and then die. We have also provided you with ways that you can troubleshoot the problem. In the majority of instances, there will be a simple rectification. 

The Carburetor May Be Dirty, Clogged, Or Worn Out

If your lawnmower is not functioning properly, you will typically find that there is a problem with the carburetor. It may be dirty, clogged, or worn out.

The carburetor is a device that is responsible for mixing the correct ratio of gas from the tank with air in the mixing chamber. It will then create combustion.

The carburetor is typically situated on the top or the side of the lawn mower’s engine. Without a steady flow of gasoline, your lawnmower will struggle to run correctly. 

Now you may be wondering how to determine if the carburetor is causing the problem. Four main signs will confirm that it is responsible.

First, if your lawnmower is equipped with a diesel-powered engine, you may notice that there is black smoke coming out of the muffler. A second sign can be identified via a deterioration in the performance of the engine.

Does it stall or feel rough when you attempt to move it? Finally, if the carburetor is faulty, there is a greater risk of the engine overheating or backfiring. 

A lawn mower’s components are going to be more exposed to problems if they are left sitting outside for the majority of the year, especially during the winter months. The carburetor can also become faulty if old fuel is left sitting inside it for prolonged periods.

Furthermore, as the fuel makes its way into the compression chamber, dirt or contaminated fuel can sometimes get stuck in the carburetor and as a result, it becomes clogged.

There is then a risk of the contaminated fuel entering the compressor, however, because it doesn’t burn correctly, even if the engine starts when you pull the cord, it isn’t going to run for very long. 

What Tools Are Required To Fix A Dirty Or Clogged Carburetor?

In most cases, the solution to this problem involves cleaning the carburetor and using fresh oil. If you are dealing with a severe problem, you may need to remove the current carburetor and swap it for a new one. 

There are a few tools and products that you can use to make the task of cleaning the carburetor easier. 

A specific carburetor cleaner is of course going to be essential. You must make sure that the formulation is safe to come into contact with the oxygen sensors and other components.

It should also be effective in removing the build up of residue that seems to be affecting how well the carburetor performs. You may also find it helpful to invest in a cleaning brush as this will allow you to work the product into the carburetor as well as making it easier to reach the more intricate parts. 

To remove the carburetor you will require the use of sockets and ratchets. By removing the carburetor you can inspect it more closely. 

If there is old gas inside the carburetor you will need to use a siphon to drain it. 

Before putting all of the parts back together, we also recommend that you use some sort of fuel treatment. This will help to keep the engine in optimal condition. 

How To Clean The Carburetor On Your Lawn Mower

To begin you will need to remove the carburetor from your lawnmower using the sockets and ratchets. Depending on the type of mower that you have you may also be able to unscrew the bottom part of the carburetor’s float bowl.

Make sure that you keep any screws that you remove in a safe clean area where they are not near any dirt. 

Once you have removed the carburetor you can then clean it using the cleaning product that you have purchased. It is important to make sure that you clean any holes on the carburetor as well.

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When you are happy that the carburetor has been thoroughly cleaned, you can then reattach it to your mower. Make sure that you do not over-tighten the screws because if you need to remove them again in the future, you may experience difficulties when attempting to do so. 

Can You Clean The Carburetor Without Removing It?

If you want to give your carburetor a thorough clean it is recommended that you remove it if you have the necessary tools to hand. However, it is possible to clean the carburetor whilst it is still attached without having to remove it. 

There are products available that can be added to the fuel in your lawnmower and they help to tackle any dirt or moisture that has accumulated. You will need to make sure that the product you choose is suitable for the engine of your lawnmower.

Whilst you will find some that are suitable for both gas and diesel engines, others may be more specific. To clean the outside of the carburetor you can use spray-on products.

Again, these types of products will help to combat any build-up of dirt and will also fight against any grease that may have leaked.

The product is likely to have specifications that state how it is intended to be used, however, in most cases, you will need to spray it onto the exterior of the carburetor before wiping it away using a cloth. 

You Are Using The Incorrect Type Of Gas Or It Has Gone Bad

Gasoline lawn mowers rely on fuel to operate, however, you will run into problems if you use the wrong type or if you leave the fuel in there for too long. Using good quality gas is of paramount importance.

If you are going to be putting your lawn mower into storage, you must make sure that you empty the fuel inside it beforehand. Gas that has been sitting idle inside a lawnmower will eventually start to evaporate.

As it evaporates it is going to leave a residue behind that can be quite damaging to your lawnmower. There is also a risk of the residue clogging up your lawn mower’s internal components. When you go to use your lawnmower again you will find that whilst it may start, the power doesn’t last for very long. 

What Should You Do If You Are Using The Incorrect Gas Or Gas That Has Gone Bad?

If the tank of your lawnmower is more than half full of gas, it is recommended that you use a siphon to drain it, then when you go to use it again ahead of a new season, you can refill it using fresh gas.

If there is some gas inside but it isn’t very full, it may be worth adding some new gas to it. It is thought that combining the old gas with the new gas will get rid of any impurities that are affecting the quality.

Furthermore, it may be worth adding a fuel stabilizer to the tank. This will enhance the quality of the gas by preventing it from getting clogged up. 

My Lawn Mower Starts Then Dies

There May Be A Problem With The Choke

The choke, also referred to as the choke valve, is responsible for controlling the flow of air into the fuel-air mixture. This component is used to start a cold engine. During the process of cold starting the engine the choke should remain closed as this will reduce the amount of air that gets into it.

Simply put, holding onto the choke increases the fuel levels and in return, the cold engine will begin to function. As the engine starts to warm up, this component is no longer needed and it can then be turned off. 

You will find it hard to start a cold engine if the choke is loose or faulty. This is because it will not supply the correct amount of fuel to the engine. 

There are a few ways that you can check to see whether the choke is the component that is causing the problem. Often you will find that the efficiency of the choke is affected by flooding in the combustion chamber. This happens as a result of too much fuel entering the top section of the engine.

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It also prevents the spark plug from working properly hence why the engine does not start. Engine flooding can also occur when the choke gets stuck in the same position. If this issue isn’t rectified, dirt and dust will begin to build up. 

How To Fix A Loose Or Faulty Choke

To resolve this issue, you will first need to identify what is causing the problem as we have highlighted above. If it seems that the choke is stuck in one position you will need to completely open it. Doing so will allow the engine to start. 

If your lawnmower initially appears to be running ok, but it stalls suddenly as you are in the middle of using it, it may be that the choke has been left on. If this is the case, you will need to turn it off. Try to avoid pulling the cord repeatedly because this does not always work. 

Finally, if you have noticed that the choke is loose you will need to tighten it. After tightening any loose screws if you notice that the problem persists you may need to completely replace the spring and invest in a new one. 

There Is Moisture In The Gas Tank Or Fuel Line

Excessive moisture in the gas tank or the fuel line can affect the performance of your lawnmower. The engine will either splutter or your lawnmower will start and then shut down again.

Not only is the moisture going to decrease the efficiency of your lawnmower, but there is also a risk of it damaging it as the tank and adjoining components may be affected by corrosion. 

What Should You Do If There Is Moisture In The Gas Tank Or Fuel Line?

The steps that you take to rectify this issue will differ depending on where you detect that there is moisture. Begin by inspecting the fuel line, if there appear to be droplets you will need to make sure that the connecting pipe is fitted properly.

Also, make sure that the seal is not damaged in any way. Of course, if there are any problems with the quality of the seal then it is going to be ineffective in keeping any foreign matter out.

As you inspect the seal, also check the pipe for any signs of cracks or holes. Again, any sort of crack or hole is going to make it easier for moisture or water to enter and affect the quality and performance of your lawnmower. 

Now, you may find that there is moisture in the gas tank. If this is the case, it is recommended that you use an additive. Adding a product of this kind to the gas will get rid of any water that is in the fuel. 

In the worst case scenario, you may be dealing with a significant build-up of moisture. The best way to overcome this problem involves draining the tank completely. You can then set it aside and make sure that you give it plenty of time to dry thoroughly. 

The Spark Plugs Are Deficient

Spark plugs play a very important role in the functioning of a lawnmower. Essentially, this component supplies the spark that then ignites the fuel and air mixture which is located inside the mower engine. This spark is the source of power. 

Deficient spark plugs are another very common reason why your lawnmower may seem more difficult to operate and start than normal. If you use a push lawnmower and you notice that you are having to pull on the start rope a lot it may be that the spark plugs are dirty or faulty.

In many instances, a lawnmower with faulty spark plugs will not start at all or it will start and run for a short while before cutting out. If the spark plugs are bad, your lawnmower may consume more gas than normal and this is because it is having to work harder. 

How To Fix Faulty Spark Plugs

The spark plugs on a lawnmower are fairly easy to locate. They are typically fitted on the front section of walk-behind lawn mowers. Before you begin playing around with these components it will help to have the user manual to hand. 

A socket wrench will be needed to remove the plugs however, you will need to make sure that the tool you use is of the correct size. After removing the plugs, if they appear to be coated in a residue, you will need to clean them thoroughly before refitting them to your lawnmower.

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Cleaning the spark plugs should make them much more efficient. If you remove the spark plugs and notice that they are extremely dirty and beyond help, you may be better off investing in new ones. 

Replacing spark plugs can seem like quite a challenging task, especially if you do not have previous experience of changing one. You must make sure that after installing the spark plug, you do not overtighten it. 

It is recommended that you check the spark plugs every time you conduct maintenance on your lawn mower. A single spark plug is thought to deliver approximately 25 hours of use.

Even if they are not faulty, it is advisable to change them annually, perhaps at the start of every mowing season. The user manual will also state the time frame that the manufacturer recommends you change the spark plugs within. This will ensure that your lawnmower is in top working condition.

The Muffler Could Be Blocked

The purpose of a muffler on a lawnmower is to reduce the noise that is produced by the exhaust. If your lawn mower’s muffler is blocked it will affect how well the engine runs. Often, it will feel rough but it can also cause the engine to die. 

Begin by visually inspecting the muffler. If you notice that there is a build-up of dirt or debris which is blocking it, you will need to clean it. Do not try to clean the muffler when it is still attached to the lawnmower, you should remove it first.

It is also important to turn the engine off and give the muffler sufficient time to cool down. It will be difficult to work with straight away because it will still be quite hot. Wear safety gloves to protect your hands during this task. 

After removing the muffler, try to remove the dirt or debris build-up using your hands. If this does not work, you can spray a cleaning product onto it. This should encourage the dirt to break down.

Once you have applied the product and cleaned it thoroughly, you will then need to let the muffler dry before you put it back on. 

There Is Too Much Oil In The Reservoir Of Your Mower

If you have inspected the other parts of your lawn mower but have yet to identify the problem, it may be that there is too much oil inside the mower’s reservoir. Overfilling the reservoir is an easy mistake to make and can easily happen to those that are filling it for the first time. 

An excessive amount of oil is going to affect how well the crankcase works. Oil will then either start to sputter out of your lawnmower or it will make it hard to start the engine. Too much oil can also cause the engine to overheat, resulting in potential damage. 

Resolving this problem is a straightforward task as you simply need to drain the oil until it returns to a normal level. Some people may find it easier to use a siphon to drain the oil. Using a dipstick is also going to be helpful because this will tell you when the oil is at the correct level. 

When Should I Contact A Professional?

You will usually find that a lawn mower struggles to start as a result of one of the problems that we have listed above. If you have inspected your lawnmower and tried to troubleshoot the problem following the steps that we have listed above to no avail, you may need to contact a professional.

If your lawnmower is still covered by the manufacturer’s warranty, you may be able to return it to the store that you purchased it from. The manufacturer will then be able to see if they can help to fix the problem.

Some engineers may also be able to come up with an effective solution. It is important to remember that your lawnmower will come with a manual. It is worth reading this thoroughly as this is where you may find some of the answers that you require.