15 Reasons Your Lawn Mower Is Stalling(+Quick Fix)

It is a bad experience when you are in the middle of mowing, and your lawn mower shuts off after working for some time. When a mower stalls, it indicates that there is some problem with it. 

Some common reason why your lawn mower is stalling includes problems with the fuel type, choke settings, spark plugs, filters, fuel lines, carburetors, fuel caps, and mower decks. Regular maintenance of the mower will keep these issues at bay and prevent stalling in the future.

This guide will explain 15 reasons behind the lawn mower turning off after some time or stalling and how to fix it.

Lawn mower 1

1. Old or bad gasoline

Old gas can gum up inside the fuel system and erode the system. 

Gas begins to break down after 30 days of purchase. So, do not let your lawn mower stay idle for long. 

Most gasoline is blended with ethanol to make it more environmentally friendly. 

The high amount of ethanol is bad for small engines like the mower. 

That is why experts recommend using gasoline with 10% ethanol and not more than that. 

Ethanol can attract moisture out of the air, which can further corrode the fuel system. 


If the fuel is old or bad, drain the fuel tank with the fuel siphon pump and gather it in a container for proper disposal. 

Refill your fuel engine with new, good-quality gas that contains 10% or less ethanol. 

Use fuels like Sea Foam SF-16 Motor Treatment – 16 oz., white to stabilize the fuel, reduce the moisture content, and clean the fuel system. 

Use the right fuel based on the engine type. 

For 2-cycle engines, use unleaded gasoline and 2-cycle oil mix. 

For 4-cycle engines, use unleaded gasoline with no oil mixture. 

2. Insufficient fuel level

Lawn mower gas refill

A low fuel level will make the machine die after a few minutes or stall. 

Using a lawn mower along the hillside area or over uneven surfaces will affect the fuel supply. 

As a result, the machine will stop after some time due to low fuel levels. 


If the mower is stalling when you run it over uneven surfaces or hillside areas, check the fuel level. 

Add more fuel to the tank if the level is too low. 

Be careful while running the lawn mower near the hillside areas. Avoid steep slopes, as they can make your mower lose fuel. 

3. Incorrect choke setting 

The lawn mower’s choke helps start the mower when the engine becomes cold. 

The choke will stop the airflow from allowing the engine to get a high gas concentration. 

Once the engine becomes hot, the choke should get adjusted for the engine to receive enough airflow and keep running.

If the choke setting is wrong or it got moved from its place, it will no longer stop the airflow and make your mower stop after some time or stall after the engine warms up. 


Make sure the choke is set in the right place. It is adjusted by turning the knob or lever on the carburetor. 

If the closer is set to OFF, the restriction will increase, making it harder for the fuel to enter the engine. 

If you have an old mower, it won’t have an adjustable choke. The opening should be fixed instead. 

Take your lawn mower to an expert to fix the choke setting. 

4. Clogged air filter 

Lawn mower cleaning

When you do not change or clean the air filters in the mower, it will get clogged by grass and debris. 

As a result, the airflow won’t be able to pass through the filter, due to which the mower will stall and shut off after some time. 

Over time, it can damage your mower’s engine and result in huge repair bills. 


You must clean or change them at least every 3 months for the mower’s smooth functioning. 

If you have paper air filters:

  • Remove the filter from the air filter housing. The cover will be attached with clips, knobs, or wing nuts. 
  • Remove the dirt in the housing. Don’t let dirt and debris fall into the air intake. 
  • Tap your fingers against the solid surface to loosen the dirt and make them fall out of the filter. 
  • Hold the filter up and try seeing through it. 
  • If you can see through the filter, you have cleaned it well. Otherwise, replace it with a new one.
  • Install the new one and reattach the housing cover. 

If you have foam filters:

  • Remove the filter from the air filter housing. 
  • Remove the leftover dirt and ensure not to let them fall into the air intake. 
  • Check the filter’s condition closely. 
  • If you see it as brittle, torn, or damaged, replace it with a new one. 
  • If the filter is in good shape, then start the cleaning. 
  • Wash the filter with detergent and water. 
  • Rinse the filter until the soap is completely removed and the water runs clear. 
  • Let it dry for some time. 
  • Coat the filter in the filter oil. This oil will trap the dirt. 
  • You should lightly saturate the filter in the oil. Oil should not drip from the filter. 
  • Install and reattach the filter with the housing cover. 

Looking for gardening supplies? We have tested 100's of products before recommending them to you guys. Check out our best pick below:

5. Bad spark plug 

Lawn mower spark plug

A dirty spark plug can shut your mower off and stall after some usage. 

You should remove the spark plug boot and the plug itself to inspect for dirty tips, broken porcelain, or burnt electrodes. 


Clean the spark plug with a dirty tip with the help of a wire brush. 

You can also replace the plug if it is very dark or damaged. 

Gap the spark plug as explained in the engine manufacturer’s manual and then install it. 

If you feel hesitant, take the mower to an expert to fix it. 

6. Clogged fuel filter 

Dirty fuel filters will damage the engine and make your mower stall or die after some time. 

A fuel filter prevents dirt and debris from entering the fuel system. The filter will filter the dirt from the fuel when it comes out of the tank. 

Clogged fuel can stop the fuel flow and make your mower stop working in between. 


Replace the filter annually or often if you use dirty fuel. 

Shut off the fuel supply with the shut-off valve on the mower and change the filter. 

If your mower has no valve, use pinch pliers to crimp the fuel line and stop the fuel flow. 

Remove the filter from the fuel line and install a new filter. Install it with the arrow pointed in the direction of the fuel flow.

The arrow must be pointed toward the carburetor and away from the fuel tank. 

7. Clogged fuel lines 

lawn mower fuel filter

The fuel can leave behind tacky deposits when it becomes old. 

These deposits can block the fuel from flowing through the lines. 

As a result, your mower will stop and stall while operating. 

To confirm a clogged fuel line, check every section of the fuel line by stopping and starting the fuel flow. 

It will let you check the flow level from each line section. 

You can also control the fuel flow with the help of the fuel shut-off valve present at the bottom of the gas tank. 

If the mower does not have a valve, pinch pliers will work in crimping the line to stop the flow. 


Once you have found the blocked section, remove the line from the mower and spray carburetor cleaner spray into the line. 

The spray will loosen the dirt and stickiness. Blow the line with the compressed air to remove the dirt and debris. 

Repeat the process until all the clogging and debris gets dislodged from the line and opens. 

If you cannot clear the line or it becomes dry and cracked, you need to replace it with a new one. 

8. Dirty carburetor 

Lawn mower engine repair 2

The carburetor is an important part of the lawn mower. 

It encourages the mower engine to run efficiently by giving the right amount of gas to mix with the air for combustion in the cylinder.

It mostly happens when you do not use your lawn mower for a long time. 

The watery component in the fuel evaporates, and the remaining fuel becomes greasy and sticky.

Old gasoline can clog the fuel jet and make the internal parts sticky. 

Whenever you try starting the mower, it will start but turn off after some time because the sticky gas will not let your mower’s internal parts function properly. 


Clean the carburetor to resolve the issue. 

One way to clean the carburetor is by using the spray cleaner. 

Use carburetor aerosol spray in the carburetor to clean it when it is already installed in the lawn mower. 

Before cleaning, make sure your machine has cooled down.

Please remove the air filter cover, the filter, and the external carburetor cover and keep them aside. 

Spray some cleaner in the air intake to clean the dirt. 

After it dries, start the engine to see if it works. If it still stalls, you need to detach the carburetor for cleaning. 

In some mowers, the carburetor will be below or behind the air filter and linked to the gas tank. 

In others, it will be on the top or side of the engine.

Gather tools:

  • ⅜ and 5/16 socket
  • Socket wrench
  • Screwdriver
  • Pliers

While working with the carburetor, wear protective gear and glasses. 

Before opening your carburetor or other components, take a picture to reassemble everything in place. 

Here are the steps to clean the carburetor:

  • Remove the air filter cover, the filter, and the filter housing. 
  • Remove the fuel hose from the carburetor and detach the screws, nuts, and clamps holding the carburetor. 
  • Detach the fuel leakage and carefully rotate and pull the carburetor until you free it from its place. 
  • Remove the screws and pin securing the float valve. Be careful while handling the valve and the gasket. 
  • In this step, some carburetors will have splash plates that you should disconnect and keep aside. 
  • Take off other screws, gaskets, the o-ring, the choke, and other hardware materials. 
  • If you have a Quantum mower, you have 3 parts for replacement – float bowl o-ring, carburetor seat, and float valve needle.
  • For cleaning, get a can of carburetor cleaner or Coca-Cola. Coke can remove rust due to the presence of citric acid.
  • Pour it into the sink and soak the carburetor and its components in the cleaner or coke for some hours. 
  • Scrub the components with a brush and use compressed air to remove the leftover debris. 
  • The main jet is another area for which the mower can stall. So, clean the jet properly and carefully. You can poke a bread tie wire through the jet’s small hole to clean it well. 
  • Do not overtighten the bolt. 
  • Double-check to see whether the hose has any holes or leakage. In that case, you have to replace it. 
  • After that, you should drain the old fuel and add new fuel to the engine’s tank. 
  • After cleaning, put every component back in its place, including the carburetor. 

9. Bad fuel cap 

Lawn Mower grass bag 2

The fuel cap in the mower is made with a vent for adequate airflow to pass through the cap. 

When the vent is clogged or broken, the fuel tank creates a vacuum and keeps the fuel from flowing out from the tank to the engine. 

As a result, your mower will shut off after some time. 

To check whether the fuel cap is the problem or not, remove the cap, and start your mower. 

Reinstall the cap if it runs fine without sputtering, stalling, or turning off. 

If the problem persists after reinstalling the cap, it means it does not allow air through the vent. 

Instead of opening, try loosening the cap to check the vent. 

If the air cannot enter the cap and creates a vapor lock, your mower will stall and die after some time. 


Replace the fuel cap with a new one. 

First, try to remove the dirt from the cap and check if it is working. If it remains the same, replace it. 

10. Clogged mower deck 

Lawn mower blade cleaning

The mower deck can get clogged with grass clippings, dirt, and debris. As a result, the mower will work hard to cut the grass. 

The engine gets strained when the blades turn through the clogged deck. 

Dull blades with clogged mowers will stretch the problem, and your machine will keep turning off. 


Clean the mower deck regularly. 

Use a deck scraper, putty knife, or wire brush to clean the mower deck, especially the underside. 

A good deck scraper is MoJack Heavy Duty Lawn Mower Deck Scraper, EZ Non-Slip Grip Handle, Stainless Steel, 10.25”.

Avoid cutting long or wet grass as they are more prone to clumping. 

The grass should not be taller than 3 inches. Cut them short if the grass is taller. 

11. Mower speed 

Lawn mower

The mower speed differs based on the mowing conditions. 

A garden with tall, thick, or wet grass should be mowed at a slower ground speed than dry ones with short and thin grass. 

Moving the mowing faster strains the engine and results in poor cuts. As a result, the mower will shut off after some time.


Adjust the ground speed according to the grass conditions. 

For taller and thicker grass, keep a low speed. For thin and dry grass, use high speed. 

Avoid cutting wet grass as they remain stuck in the mower deck. 

For taller grass, maintain multiple cuts. It may take time, but the results will be better, and your mower will work fine. 

12. Bad safety switch 

Lawn mowers have safety switches to keep the machine safe. 

The switch’s types and numbers vary based on the type of mower. 

One of these switches will make your machine die and stall after some time when it fails to sense the operator. 

It could be the safety bar on the push mower or the seat switch on the riding mower. 

The switches can become bad or fail to make a good connection, making your mower stall and turn off after a few minutes. 

It happens when the mower mows during very bumpy conditions. 

Bouncing in the seat weakens the connection with the seat switch, thus cutting off the engine. 


Test the safety switch with a multimeter. 

Do not operate your mower without the safety switches. 

If they go bad, you should fix them with the help of an expert and then use the machine. 

13. Excessive oil in the crankcase 

Lawn mower gas

Overfilling oil can make your mower smoke because the engine will burn off the extra oil. 

Such a condition can turn off and stall your mower. 

Excessive smoke will block the air filter if the engine oil cannot pull the clean air, for which the mower will shut down. 


Make sure not to overfill your mower. 

If you have a small amount of excess oil, it should burn off, and the smoke should disappear once the oil has burnt off. 

14. Damaged cooling system 

The cooling fins in lawn mowers can get damaged due to excessive grass and mud buildup. 

When this happens, the fins cannot circulate air around the engine block to cool it down. 

Your mower will overheat and shut off after some time of mowing. 


Remove the engine cover to clean the cooling fins. 

Replace the damaged fins by consulting an expert. 

Remove the dirt and debris around the engine and engine cover for adequate airflow. 

15. Faulty ignition coil

Lawn mower spark plug removal

The winding in the ignition will detach when the mower overheats. Due to this, the spark plugs will fail to receive voltage to create the spark. 

It will shut your mower off and stall after running for a while.


Use an Ohm meter to detect the faulty ignition coil and replace it if you find any breakage. 

Consult an expert for replacement. 

Final thoughts

Since a lawn mower is a machine, it won’t come without issues or frustrations. Various reasons could be responsible for a lawn mower to stall or die while operating. If you have owned a mower for too long, you will face the above issues at some point. 

So, prepare yourself to face these issues and know ways of troubleshooting them. This guide can help you identify and deal with the problems. 

Regular maintenance and using the right fuel type can keep your mower safe in the long run. 

Why does a lawn mower overheat?

The primary reasons behind an overheated lawn mower are low engine oil, wrong oil type, clogged filters and mower deck, damaged engine guard, dull blades, and overworking engine.

Why is my lawn mower not cutting grass?

When your lawn mower does not cut grass, it could be because of dull blades, a dirty mower deck, or tall, thick, and wet grass.


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.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts