Troubleshooting Guide: What to Do When Your Lawn Mower Won’t Start

Landscaper starting his riding mower

If your lawn mower won’t start, try checking the following; that you have enough fuel, the spark plug is clean, the air filter is not blocked, that the ignition switch is engaged, and that the mower battery has a charge.

Few things can be as frustrating as getting ready to mow your lawn on a sunny day, only to discover that your lawn mower won’t start. Whether you have a small push mower or a large riding mower, starting issues can happen anytime, leaving you feeling helpless and unable to maintain your yard.

A reliable lawn mower is essential for any homeowner, and keeping it in good working condition is critical to keeping your lawn looking its best. Throwing in the towel and calling a repair technician can be tempting when it won’t start, but many starting problems can be fixed with simple troubleshooting.

This article will provide a guide to help you troubleshoot your lawn mower when it won’t start.

From checking for common issues to advanced troubleshooting techniques, we’ll walk you through diagnosing and repairing the problem. We’ll also provide tips for preventative maintenance to help you avoid starting issues in the future.

Preparing to Troubleshoot Lawn Mowers

Lawn mower man start up the engine

Before troubleshooting your lawn mower, taking some safety precautions to avoid injury is essential.

Always wear protective eyewear and gloves, and ensure the engine is turned off and cool before you begin. Disconnecting the spark plug wire would be best to prevent accidental starting while working on the mower.

Once you’ve taken these safety measures, gather the necessary tools and materials for troubleshooting. This may include a socket set, pliers, screwdrivers, and a multimeter for testing electrical components. Depending on what you discover during troubleshooting, you may also need replacement parts, such as a new air filter.

It’s also a good idea to consult the owner’s manual for your lawn mower to see if there are any specific troubleshooting tips or instructions.

The manual may also provide information on recommended maintenance schedules and procedures, which can help you keep your lawn mower in good working condition and prevent future starting problems, as well as extend its life.

By taking these preparatory steps, you’ll be ready to begin troubleshooting your lawn mower confidently and minimize the risk of injury or further damage to the machine.

Checking for Common Issues

When your lawn mower won’t start, several common issues could be to blame. By checking for these issues first, you can quickly diagnose the problem and determine whether more advanced troubleshooting is needed.

Fuel Level and Quality

The fuel level and quality are the first to check when your lawn mower won’t start or move forward or reverse. First, ensure enough fuel in the tank and that it’s not stale or contaminated. If the fuel is old, drain the tank and refill it with fresh fuel.

Spark Plug

A faulty spark plug is another common cause of starting issues. Remove the spark plug and inspect it for damage or wear. If the electrode is worn down or the porcelain is cracked, change it to a new one. You should also check the gap and adjust it if necessary.

Air Filter

A clogged or dirty air filter can restrict airflow to the engine, making it harder to start. First, remove the air filter and inspect it for dirt or debris. Then, clean it with compressed air or change it to a new one if it’s dirty.


A dead battery could be the culprit if your lawn mower has an electric starter. First, test the battery with a multimeter to ensure it has enough voltage to start the engine. If the battery is dead, get a replacement.

You can quickly determine whether more advanced troubleshooting is needed by checking for these common issues. If none of these issues are present, move on to advanced troubleshooting techniques to diagnose the problem.

Advanced Troubleshooting Techniques

If you’ve checked for common issues and your lawn mower still won’t start, it’s time to move on to more advanced troubleshooting techniques. Here are a few things to try:

Cleaning the Lawn Mower’s Engine and Carburetor

A clogged or dirty carburetor can prevent fuel from reaching the engine, causing starting issues. You may even see the lawn mower smoking or emitting black smoke.

Remove the carburetor and clean it from dirt and grass clippings with a carburetor cleaner and a wire brush. Then, reassemble the carburetor and try starting the engine again.

Testing the Ignition System

If the spark plug and battery are in good condition, but the engine still won’t start, the ignition system may be faulty. Use a multimeter to test the ignition coil and other ignition system components. Change any faulty parts.

Inspecting the Flywheel Key

The flywheel key may be sheared if the engine turns over but won’t start. Remove the flywheel and inspect the key. If it’s damaged, change it to a new one.

Checking the Fuel Lines

If fuel isn’t reaching the engine, there may be a problem with the fuel lines. Inspect the fuel lines for damage or leaks, and change any damaged lines. You can also test the fuel pump to ensure it functions properly.

These advanced troubleshooting techniques may require some mechanical knowledge and expertise, so it’s best to consult a professional if you’re uncomfortable performing these tasks. However, with some basic tools and know-how, you can often diagnose and repair starting issues independently.

Fixing the Problem

Man mowing the lawn in his garden

Once you’ve identified and diagnosed the issue with your lawn mower, it’s time to fix the problem beneath the mower deck. Depending on the issue, you may need to replace or repair specific components. Here are some possible solutions to common starting issues:

Replacing the Spark Plug

If the spark plug is faulty, get a replacement. Also, use the correct type for your lawn mower model.

Cleaning or Replacing the Air Filter

If the filter is dirty or clogged, clean it with compressed air or change it. A clean filter ensures the engine receives enough air for proper combustion.

Repairing or Replacing Faulty Ignition Components

If the ignition is faulty, repair or replace any damaged components. This may include the ignition coil or other ignition components.

Fixing Fuel Line Issues

If there’s a problem with the fuel lines, repair or replace any damaged or leaking lines. Test the pump to ensure that it’s functioning correctly.

By fixing the problem, you can start your lawn mower and get back to maintaining your lawn. Remember to perform regular maintenance on your lawn mower to prevent starting issues in the future. This may include replacing the filter and checking spark plugs regularly.

Preventative Maintenance Tips

Preventing starting issues with your lawn mower is often easier than fixing them. Here are some preventative maintenance tips to keep your lawn mower running smoothly:

Check the Oil Regularly

Check the oil level regularly and change the oil as the manufacturer recommends. Low oil levels can cause engine damage and starting issues.

Replace the Air Filter

Replace the filter as the manufacturer recommends, as it’s essential. A dirty or clogged filter can restrict airflow to the engine, making it harder to start.

Keep the Fuel Tank Fresh

Stale or contaminated fuel can cause starting issues. Use fresh fuel and add a fuel stabilizer if your lawn mower sits for an extended period.

Clean the Carburetor

Clean the carburetor as recommended by the manufacturer. As mentioned earlier, a dirty or clogged carburetor can prevent fuel from reaching the engine, causing starting issues.

Store the Lawn Mower Properly

Store the lawn mower in a dry, covered area when not in use. This will help prevent rust and other damage that can cause starting issues.

These preventative maintenance tips can keep your lawn mower running smoothly and prevent starting issues. Regular maintenance can also extend the lifespan of your lawn mower and save you money on repairs in the long run.


It can be frustrating when a lawn mower won’t start, but it doesn’t have to be daunting. Following the troubleshooting tips in this article, you can identify and diagnose the issue with your lawn mower. From there, you can use advanced troubleshooting techniques and fixes to get your lawn mower running again.

Preventative maintenance is also crucial to preventing starting issues with your lawn mower. You can avoid many common problems by regularly checking the gas tank, oil, filter, and spark plug and keeping the fuel and fuel filter fresh.

Remember, safety is also essential when working on riding mowers. Always ensure the lawn mower is turned off and cool before working on it. Wear appropriate safety gear, such as gloves and safety glasses, and follow the manufacturer’s instructions for maintenance and repair.

Do all these to keep your lawn mower running smoothly and have a beautifully manicured lawn all season long.

Happy mowing!

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Michael Harrison

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