9 Reasons Your Lawn Mower Is Turning Over But Not Starting

If you are trying to start your mower after a long time and it is not getting started, this can piss you off. But you don’t need to feel bad, as we will provide you with a troubleshooting guide to help you determine and fix the issue. 

If your mower is turning over but not starting, it is because the carburetor can be blocked with dirt or it is not getting enough air due to a blocked air filter. Other reasons include a defective spark plug, blocked fuel filter, old fuel, incorrect choke setting, or a defective fuel pump.

This article will discuss all possible reasons why your mower is not starting, so keep reading. 

Lawn mower 1

Why is your mower turning on but not starting? 

There can be many reasons for your mower to turn on but not start.  

From blocked air filters to dirty carburetors, we will discuss all the reasons in this article.  

Let us discuss all of them one after another: 

The air filter is blocked 

If the air filter is blocked, it will be difficult for your mower to start. 

This can happen if dirt enters the air filter, and it can also damage the engine. 

The engine requires sufficient air to run, but if it is blocked by dirt and other blocking components, the air passage will be blocked.

That is why you need to clean the air filter at regular intervals. 

I always start the mowing season with a new air filter, which works for me. 

You can also try this if you are using your mower after winter or after a long interval. 

If you’re confused about which filter to use, read the user manual, and you will know which one is suitable for your mower.

How to clean the air filter?

Firstly, you will need to remove the spark plug after turning off the engine. 

Then remove the air filter and ensure no dirt is spilled in the engine. 

You can wash it with water and dish soap if it is a foam filter.

You can squeeze out all the water after cleaning it. 

Once it is dry, coat it with lubricating oil. 

If the filter is torn and not good enough to use again, then you will need to replace it. 

If it is a paper filter, you will need to take it out and tap it to remove all the dirt, and if you see it is damaged, you will need to replace it. 

Also read: Can You Run A Lawn Mower Without An Air Filter?

The choke setting is not correct. 

A choke is used to regulate the airflow through the carburetor. 

If the engine is cold, likely, the choke is not engaged, and therefore the engine gets more fuel instead of air.  

You will need to adjust the choke lever once the engine has warmed up to get enough air and fuel to run. 

Both warm and cold engines will have difficulty starting if the choke setting is incorrect. 

Therefore, you must ensure the choke is set correctly for your mower to start without fuss. 

The choke cable must also be checked to see whether it moves freely. 

If the choke cable is damaged, you will need to replace it. 

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The fuel is old

Lawn mower gas refill

Gas is a fuel that starts to disintegrate in a month after you purchase it.  

Once old gas breaks down, it leaves behind varnish and sticky deposits. 

This can cause the failure of the components of your mower.  

Also, do not forget to empty your mower’s fuel tank if you are not using it for more than a month. 

You can use a fuel siphon pump to drain the fuel tank. 

Once you have replaced the fuel with a fresh one, try to start the lawnmower and keep the engine running for a few minutes. 

This will help the fuel to run through the system. 

If you cannot start the engine yet, then there is some problem with the fuel filter, and it is blocked, which we will discuss later in this article. 

Also read:

A spark plug is not clean. 

You will need to take out the spark plug with the help of a socket wrench. 

Then you will need to check what kind of state it is. 

If you find it dirty or spoilt, check if it has a dark tip, broken proclain, or burnt electrode. 

If you see any of the above issues, get a new one.

If you see that the gap in the plug is okay, then reinstall it after cleaning. 

Starting the mowing season with a new spark plug will be a good idea.

Also read: Why Is My Lawn Mower Spark Plug Wet? (3 Possible Problems+Fix)

The fuel filter is blocked.

lawn mower fuel filter

There’s always a fuel filter that prevents dirt and debris from entering the fuel system. 

The fuel filter is fitted into the fuel lines. 

If you don’t replace the fuel filter, it can become blocked with dirt. 

If this happens, the fuel will be restricted, and the engine will not start.

Also read: 16 Easy To Follow Steps To Clean Lawnmower Fuel Filter

The carburetor is not clean. 

The carburetor’s job is to provide a proper mixture of gas and fuel to the engine to get it started with the help of combustion. 

You can’t start your mower if the carburetor is not working. 

Usually, when the carburetor is not working, the most common reason is old fuel. 

The fuel jet can be blocked by the dirt produced by the old fuel. 

If you see the carburetor is not working properly, you will need to clean it. 

If it still does not work, you will need to replace it. 

How to replace the carburetor?

Firstly, check if the carburetor is receiving a sufficient amount of fuel. 

Then you will need to check the air filter. 

If there is any minor blockage in the carburetor, you can try to clean it with the carburetor cleaner and try to start the mower. 

If it does not start, the carburetor is still dirty and needs cleaning. 

You can remove the carburetor and start cleaning it; if it is not working, you can replace it. 

A bad fuel pump

Lawn mower engine repair

If the carburetor in your mower is placed higher than the fuel tank, it means the lawn mower is using a fuel pump. 

If this fuel pump is not working properly, the fuel will not be pumped into the carburetor, so the engine will not start. 

Most lawnmowers use the vacuum of the crankcase to pump fuel because vacuum pumps are used in most lawnmowers. 

If there is any crack in the crankcase, fuel will not be pumped through for lack of vacuum. 

So, you need to check if there is a crack in the pump’s crankcase. 

If you see that the pump is receiving the fuel but cannot pump it through to the carburetor, check if the pump is leaking the fuel. 

You can also remove the fuel line from the carburetor and check if the pump can pump the fuel through to the fuel line. 

If you don’t see a proper flow of fuel, then there is some defect in the pump, and you will need to replace the pump.  

Instead of a vacuum pump, if there is an electronic fuel injection pump, you will need to measure the pump’s pressure. 

If the pressure is below, as stated in the user’s manual, you might need to replace the pump. 

Also read: 4 Signs That Your Lawn Mower Engine Is Blown (+Fix)

The fuel line is clogged.

Check if anywhere the fuel line is twisted, which is preventing the fuel from getting into the carburetor. 

If you don’t find any twist or knot in the fuel line, you will need to check where the fuel is getting restricted. 

Check if there is any blockage in the fuel line, turn the fuel supply off, remove one end of the fuel line from the carburetor, place it into a separate container, and then turn the fuel supply on.  

If the fuel is not flowing properly through the fuel line, remove it and clean it. 

Replace it with a new one if this does not work. 

The fuel vent in the gas cap is blocked.

Lawn mower bag

A vent in the gas cap maintains the air pressure in the tank.

If this vent is closed or blocked for some reason, a vacuum will be created inside the fuel tank, due to which the fuel will not reach the carburetor, and the lawn mower will not turn on.  

To check if there is any problem with the gas cap, you need to start the lawn mower after making the gas cap loose. 

If it then starts, there is a problem with the vent and the gas cap. 

Close the gas cap tightly again and see whether the engine is still running. 

If it stops, the gas cap has an issue and needs to be replaced. 

Final thoughts 

Usually, when you are trying to start your mower after a long interval, it won’t start. This article discussed why it would not start even after turning over. And what are all those things you need to check before replacing any parts? 

The problems can start from old fuel, choked settings, blocked fuel filter, bad pump, a blocked carburetor, etc. And this article will guide you step by step on how to troubleshoot. 

Make sure you do not touch a hot engine before starting any troubleshooting, and read the user’s manual for your mower before taking any major decision. 

Why my lawn mower won’t turn over with a new battery? 

There can be a problem with the connections, so check if the terminal wires are connected properly to the battery and check the battery posts.  

Why my riding mower does nothing when I turn the key? 

There might be a problem with the solenoid. So, you will need to check it with a digital multimeter and replace it if required.

Reference: Lawn Mower Technology, Lawn Mower SafetyLawn MowingLawn CareMowing your lawn.


Hello everyone, My name is Richa and I am here to make you a better gardener by creating an in-depth and helpful resource for all the fellow gardeners out there. If I could help even a few people understand their plants better then I call it a success for my efforts.

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