Why Won’t My Lawn Mower Start? A Comprehensive Troubleshooting Guide

The sun is shining, the birds are singing, and you’re ready to tackle your overgrown lawn. But when you pull the cord on your trusty lawn mower, all you hear is a frustrating “click” or a disheartening silence. What’s a homeowner to do? Don’t panic! This comprehensive guide will walk you through the most common reasons why your lawn mower won’t start and offer simple solutions to get you back to mowing in no time. We’ll cover everything from basic checks like fuel and spark plugs to more complex issues like carburetor problems.

Quick Overview:

There are several common reasons why a lawn mower may not start. The most frequent culprits include:

  • Lack of fuel or a clogged fuel line: The mower needs fuel to run!
  • Old or bad gas: Over time, gasoline can degrade and become unusable.
  • Dirty or faulty spark plug: A spark plug is crucial for igniting the fuel.
  • Clogged air filter: A dirty air filter restricts airflow and can prevent proper combustion.
  • Issues with the carburetor: This component mixes fuel and air for combustion.
  • Dead battery (for electric mowers): Electric mowers rely on a battery to operate.

Fuel and Spark: The Basics

Before diving into more complex troubleshooting, let’s start with the basics.

1. Check the Fuel

  • Is the gas tank empty? This might seem obvious, but it’s a common oversight.
  • Is the fuel old? Gasoline can go bad after a few months, especially if it’s not stabilized. Old gas can gum up the fuel lines and carburetor, preventing the mower from starting.
    • Solution: If your gas is old, drain it and replace it with fresh, stabilized fuel.
  • Are the fuel lines clogged? Over time, dirt and debris can accumulate in the fuel lines, blocking the flow of gas to the carburetor.
    • Solution: Check the fuel lines for any visible blockages. If you find any, try cleaning them with a small wire or compressed air. If you suspect a more serious clog, you may need to replace the fuel line.

2. Inspect the Spark Plug

  • Is the spark plug dirty or corroded? A dirty or corroded spark plug can prevent a spark from reaching the fuel-air mixture.
    • Solution: Remove the spark plug and inspect it. If it’s dirty, clean it with a wire brush or replace it with a new one.
  • Is the spark plug gapped correctly? The spark plug gap needs to be within the manufacturer’s specifications.
    • Solution: Consult your mower’s manual for the correct gap and use a spark plug gap tool to adjust it if necessary.

3. Test the Spark Plug

  • Does the spark plug spark? This is a critical step in troubleshooting a lawn mower that won’t start.
    • Solution: Remove the spark plug wire from the spark plug. Hold the spark plug to a grounded metal surface (like the engine block) and pull the starter cord. If you see a blue spark, your spark plug is working. If not, you may need to replace the spark plug or investigate further electrical issues.

Beyond the Basics: Air and Fuel Mixture

Once you’ve ruled out fuel and spark issues, it’s time to look at other potential problems:

4. Clean or Replace the Air Filter

  • Is the air filter dirty? A clogged air filter restricts airflow to the engine, preventing proper combustion.
    • Solution: Locate the air filter, usually found under a cover near the engine. Remove the filter and inspect it. If it’s dirty, clean it with soap and water or replace it with a new one.

5. Check the Carburetor

  • Is the carburetor dirty or clogged? This is a common problem in lawn mowers that haven’t been used regularly. The carburetor mixes fuel and air, and over time, debris can build up and disrupt this process.
    • Solution: If you suspect a carburetor issue, you can try cleaning it yourself or take your mower to a qualified mechanic. Cleaning a carburetor requires patience and specialized tools. It’s often easier and more cost-effective to have a professional do it.

6. Examine the Fuel Lines

  • Are the fuel lines cracked or leaking? Cracked or leaking fuel lines can cause air to enter the fuel system, preventing the mower from starting.
    • Solution: Inspect the fuel lines for any signs of damage. If you find any cracks or leaks, replace the affected fuel line.

Electric Mowers: The Power Source

If you own an electric lawn mower, you have a different set of troubleshooting steps to consider:

7. Check the Battery

  • Is the battery dead? Electric lawn mowers run on batteries, and a dead battery will prevent the mower from starting.
    • Solution: Check the battery level on your electric mower. If the battery is dead, charge it or replace it with a new one.
  • Is the battery connection loose or corroded? Loose or corroded battery connections can prevent the battery from supplying power to the mower.
    • Solution: Clean the battery terminals with a wire brush and ensure the connections are secure.

Don’t Forget the Manual!

Before you start troubleshooting, consult your lawn mower’s manual. It contains specific instructions and information about your model, including details about:

  • Fuel type and requirements
  • Spark plug specifications
  • Air filter location and maintenance
  • Carburetor adjustments
  • Battery information for electric mowers

When to Call a Professional

If you’ve tried all the troubleshooting steps above and your lawn mower still won’t start, it’s time to call a professional mechanic. Some problems, like a faulty ignition system or a damaged engine, require specialized knowledge and tools to repair.

Preventing Future Problems

  • Use stabilized fuel: Always use stabilized fuel to prevent it from going bad.
  • Maintain regular maintenance: Regular maintenance, like cleaning the air filter and changing the spark plug, can prevent many starting issues.
  • Store properly: Store your lawn mower properly during the off-season to prevent rust and damage.


A lawn mower that won’t start can be frustrating, but by understanding the common culprits and following these troubleshooting steps, you can likely get your mower up and running again. Remember to always consult your mower’s manual for specific instructions and to seek professional help if you encounter more complex problems. Now, go forth and conquer your lawn with confidence!


Q1: My lawnmower makes a clicking sound but won’t turn over. What’s wrong?

A: This clicking sound often indicates a problem with the starter motor. The starter motor engages the engine’s flywheel, allowing it to turn over and start. The clicking means the motor is trying to engage but isn’t able to. This could be due to a dead battery, a faulty starter motor, or even a problem with the wiring connecting the starter motor to the battery.

Q2: The engine turns over but won’t start. What’s the issue?

A: If the engine is turning over but not starting, the issue likely lies with the fuel system or the spark system. This could be caused by a lack of fuel reaching the engine, a faulty fuel line, a clogged air filter, or a problem with the spark plugs or ignition coil. Inspect these components for any blockages or damage.

Q3: My lawnmower starts but dies immediately. What could be the cause?

A: A lawnmower that starts but dies immediately suggests a problem with the fuel supply or the ignition system. The engine might not be getting enough fuel, or the fuel might be contaminated. Alternatively, the spark plugs could be faulty or the ignition coil might be malfunctioning. It’s crucial to check the fuel lines and filter for any blockages.

Q4: I’m experiencing trouble with my lawnmower’s spark plugs. What should I do?

A: Spark plugs are crucial for igniting the fuel mixture in your lawnmower. Over time, they can become fouled with carbon deposits or wear down, impacting their performance. The solution is to replace them with new spark plugs of the correct type for your lawnmower model. Regularly cleaning or replacing spark plugs will ensure efficient ignition.

Q5: I can’t seem to find the fuel shut-off valve. Where is it?

A: The fuel shut-off valve’s location varies depending on the lawnmower model. It’s usually situated near the fuel tank or the carburetor. Look for a lever or knob that controls the fuel flow. Often, the valve is marked with “ON” and “OFF” or has an arrow indicating the direction of fuel flow.

Q6: My lawnmower’s carburetor is clogged. How can I clean it?

A: A clogged carburetor can prevent fuel from reaching the engine. You can clean it yourself using a carburetor cleaner spray and a small brush. First, disconnect the fuel line and remove the carburetor from the engine. Carefully spray the carburetor cleaner into all the openings and jets, then use the brush to loosen any stubborn deposits. Once cleaned, reassemble the carburetor and reconnect the fuel line.

Q7: My lawnmower won’t start after being stored for a long time. What should I do?

A: After prolonged storage, the fuel in the tank can become stale and gum up the engine. To resolve this, you need to drain the old fuel and replace it with fresh fuel. Additionally, clean the carburetor to remove any fuel deposits. Finally, make sure the battery is charged or replaced if necessary.

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