7 Reasons Your Lawn Mower Won’t Stay Running

by Jack Grover
person checking on mower engine
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If you’re frustrated with your lawn mower constantly stalling and refusing to stay running, you’re not alone. There are several potential reasons for this common issue, but don’t worry — we’ve got you covered.

Below, we explore the most likely culprits behind your mower’s temperamental behavior and provide solutions to get it back up and running smoothly.

Bad or old fuel, a clogged fuel line, or a dirty carburetor can lead to engine problems and hinder proper combustion.

Here’s how to resolve these and other issues that prevent your lawn mower from humming along happily all season long.

Key Takeaways

  • Clogged and dirty air filters can cause a lawn mower to stop running and result in a loss of power. Regular maintenance and cleaning of the air filter is necessary.
  • Spark plugs should be replaced every season or after 100 hours of use. Cleaning and checking the spark plug for moisture or corrosion is critical for proper ignition.
  • The fuel system, including the fuel line, fuel filter, and carburetor, should be regularly inspected and cleaned to prevent clogs and restrictions that can cause the lawn mower to stall.
  • Proper maintenance of the choke system, fuel cap vent, and fuel pump is necessary to ensure the delivery of clean fuel and prevent engine damage. Using fresh fuel with the appropriate octane and alcohol rating is also important.

Bad or Old Fuel

person pouring fuel in mower

If you’ve been neglecting your lawn mower’s fuel, it’s time to face the consequences.

Stale fuel, which has been left unused for a long time, can attract moisture and lead to corrosion in the fuel system. It can cause the engine to perform poorly and eventually result in your mower stalling.

So, what can you do to prevent these problems?

The first step is to use a fuel stabilizer to clean the fuel system and remove any moisture buildup.

Additionally, make sure to regularly drain old fuel from the tank and replace it with fresh gasoline. Doing so will ensure proper fuel delivery and keep your lawn mower running smoothly.

Clogged Fuel Line

When your mower suddenly stalls, it may be due to a clogged fuel line. This component carries fuel from the tank to the carburetor. Without it, your mower won’t run.

Over time, debris, old fuel, and dirt can accumulate in the fuel line, blocking the flow of fuel and causing your mower to sputter or die. To fix the problem, you’ll need to turn off the fuel supply and disconnect the fuel line from both ends.

Use either carburetor cleaner or compressed air to free the line from obstructions.

If the blockage persists, you may need to get a new fuel line.

Clogged Fuel Filter

A clogged fuel filter can be a major issue for lawn mower performance. It restricts the flow of fuel, resulting in engine stalling.

You should regularly inspect and clean the fuel filter to keep your mower functioning correctly.

Start by removing dirt and debris from the filter. If cleaning doesn’t resolve the issue, replace it with a new one.

Still, don’t buy the first fuel filter you see. Instead, get the correct model that’s specific to your mower.

Routine maintenance is also essential. Check for any signs of clogging or damage. Address and resolve the clogged fuel filter promptly to ensure smooth and efficient operation.

Dirty Carburetor

A dirty carburetor can cause a lack of fuel and make it difficult for your mower to stay running.

To clean your carburetor, turn off the fuel valve and remove the fuel line and overflow hose.

Loosen the clamps and disconnect the cable from the lawn mower. Take apart the float bowl and unscrew any screws. Use needle-nose pliers to remove the float pin and float, taking care not to damage any gaskets.

Next, remove the splash plates to access the jets. Clean the jets, float needle, and any other parts with carb cleaner by spraying or soaking them.

Scrub with a wire brush to ensure a thorough clean. Use compressed air to blow all parts dry before reassembling. Put everything back together in the reverse order you took it apart.

If all of this cleaning doesn’t improve the performance of your lawn mower, contact a professional mechanic for assistance.

Clogged Air Filter

Another reason for having trouble with your lawn mower could be a clogged air filter. This filter is the first line of defense against dust and dirt, but it can become blocked. In such a case, the airflow is restricted, leading to a lack of power.

To address this issue, clean the filter housing with a dry cloth.

Then, check for any cracks or tears in the air filter itself. If it’s a foam filter, you can wash it in warm water with a gentle detergent.

If necessary, you can also buy a new filter that’s compatible with your lawn mower model and replace the old one.

Remember to replace your paper or foam filters once a season.

Dirty Spark Plug

Spark Plug

A dirty spark plug is one of the most common causes of lawn mower frustration.

When a spark plug gets clogged with carbon or oil deposits, it can’t create a strong spark. It can cause your mower to run rough or fail to start.

The gap between the electrodes should be correctly set for optimal performance. If it’s too large or too small, it can affect the ignition process.

Finally, the ignition coil needs to be in good working order. It generates the high voltage needed for the spark. If it’s faulty or its windings have separated and shorted out, your mower won’t start.

Bad Lawn Mower Fuel Cap

Maintaining your lawn mower’s fuel cap is crucial for keeping it running smoothly. A blocked or damaged fuel cap can prevent the engine from receiving the fuel it needs, resulting in stalling or complete engine failure.

If you suspect your fuel cap is clogged, inspect it carefully. Debris and dirt can build up in the vent, blocking the passage of fuel. This situation restricts the proper combustion of the engine, leading to problems with operation.

To fix the issue:

  1. Take the fuel cap off and check for signs of blockage or damage.
  2. Clean out any debris using a soft brush or compressed air.
  3. If needed, replace the fuel cap with a new one to ensure fuel flows into the engine unhindered.

The Bottom Line

So there you have it — seven common reasons why your lawn mower won’t stay running. 

From bad or old fuel to clogged fuel lines, filters, and carburetors, these issues can prevent your mower from operating correctly.

Regular maintenance is vital to preventing these problems. Nevertheless, it’s best to consult a professional mechanic if these issues persist. They will help you diagnose and fix the issue in no time.

Keep your lawn mower in top shape for a perfectly manicured lawn every time!

Frequently Asked Questions

How often should I clean or replace my air filter?

You should clean or replace your air filter at least once a season or after every 25 hours of use. It ensures proper airflow and prevents dirt and debris from entering the engine, which can cause it to stall.

What steps should I take to clean a dirty carburetor?

To clean a dirty carburetor:

  1. Turn off the fuel valve and remove the carburetor.
  2. Take it apart, scrub it with a wire brush, soak it in carb cleaner, and blow dry all parts.
  3. Reassemble and reinstall.

How can I determine if my spark plug is faulty?

To determine if your spark plug is faulty, you can visually inspect it for carbon or oil buildup. Check the spark plug gap and ensure the wires are securely attached. Use an ohmmeter to test for continuity breaks.

What are the signs of a clogged fuel line?

Signs of a clogged fuel line include engine stalling, lack of power, and difficulty starting. You may also notice sputtering or surging while the mower is running. Clean the line with carburetor cleaner or replace it if necessary.

How often should I replace my fuel filter?

You should replace your fuel filter every year or after 100 hours of use to ensure proper fuel delivery and prevent clogs.

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