Lawn Mower Won’t Start: Troubleshooting and Quick Fixes

lawn mower
Tinseltown /

A lawn mower that won’t start can be a frustrating issue for homeowners looking to maintain their yards. Various factors may be preventing the mower from starting, such as bad fuel, a dirty spark plug, or clogged air filter. Addressing these potential issues can help return the mower to its proper functioning, making it easier for individuals to tackle their lawn care tasks.

The first step in diagnosing a non-starting lawn mower is to check the fuel levels and ensure there is enough gasoline to operate the machine. Additionally, inspecting the air filter for any debris or clogs that may be obstructing airflow is essential in allowing the engine to start. Cleaning or replacing the air filter, as needed, will help the mower function more efficiently.

Another common issue that prevents lawn mowers from starting is a dirty or improperly connected spark plug. By disconnecting the spark plug wire and inspecting the plug itself, homeowners can determine if cleaning or replacing it is necessary. Removing any build-up on the plug can greatly improve the mower’s ability to start and run smoothly.

Identifying The Problem

When your lawn mower won’t start, it can be frustrating and time-consuming to find the cause. To help you identify the problem, we have narrowed down three common reasons: checking the spark plug, examining the fuel system, and inspecting the air filter. By addressing these issues, you can potentially get your lawn mower up and running in no time.

Checking The Spark Plug

One of the first things to check when your lawn mower won’t start is the spark plug. A faulty or dirty spark plug can prevent the engine from receiving the necessary spark to start. To inspect the spark plug:

  1. Remove the spark plug from the engine.
  2. Examine the tip for signs of wear, such as rounding or breakage. If it’s in bad condition, replace it.
  3. If the tip is covered in grime or build-up, try cleaning it with sandpaper.

A clean, properly functioning spark plug is essential for your lawn mower’s engine to start successfully.

Examining The Fuel System

Another common reason for a lawn mower not starting is issues with the fuel system. This can include several factors, such as:

  • No fuel in the tank
  • Bad or old gasoline
  • Clogged fuel filter or fuel line
  • Dirty carburetor

To address these issues, perform the following steps:

  1. Check the fuel tank and make sure there is an adequate amount of fuel.
  2. Replace any old or bad gasoline.
  3. Inspect and clean or replace the fuel filter and fuel line if they are clogged.
  4. Clean the carburetor, ensuring any dirt or debris is removed.

A properly functioning fuel system is crucial for a lawn mower to start and run efficiently.

Inspecting The Air Filter

A clogged or dirty air filter can also prevent your lawn mower from starting. The air filter protects the engine and carburetor from debris, such as grass clippings and dirt. To inspect and clean the air filter, follow these steps:

  1. Remove the air filter from the mower.
  2. Check for dirt or debris and clean it using compressed air or replace it with a new one if it’s too dirty.
  3. Reinstall the air filter, ensuring a proper fit.

By maintaining a clean air filter, you can improve the performance of your lawn mower and prolong its lifespan.

Basic Troubleshooting Methods

When your lawn mower won’t start, there are several basic troubleshooting methods you can use. Here are some essential steps to get your mower up and running again.

Cleaning Or Replacing The Spark Plug

The first thing to do is to check the spark plug. A dirty or faulty spark plug can prevent your mower from starting. Remove the plug, clean it with a wire brush, and check for any damage. If the plug is damaged or severely corroded, it’s better to replace it with a new one. After cleaning or replacing the plug, make sure to tighten it securely and reattach the spark plug wire.

Draining Old Fuel And Refilling

Old fuel left in your mower can cause starting issues. Check the fuel in the tank and drain it if it smells stale or looks contaminated. Dispose of the old fuel responsibly and refill the tank with fresh gasoline. It’s also essential to ensure that there is enough fuel in the tank for the mower to operate.

Changing The Air Filter

A clogged air filter can also prevent your mower from starting. The air filter protects the carburetor and engine from debris such as grass clippings and dirt. To change the air filter, locate it in your mower (usually near the carburetor), remove the cover, and replace the filter with a new one. Make sure the new filter fits snugly and that the cover is secured back in place.

These troubleshooting steps should help identify and resolve common issues with your lawn mower. Keep in mind that more significant problems may require professional assistance.

Advanced Techniques

In this section, we will discuss some advanced techniques for troubleshooting a lawn mower that won’t start. These methods are for those who have experience in working with lawn mowers and small engines.

Rebuilding The Carburetor

A clogged carburetor may cause difficulties in starting your lawn mower. To resolve this issue, disassemble and clean the carburetor. Follow these steps:

  1. Disconnect the spark plug to ensure there is no accidental engine start.
  2. Drain the fuel from the tank, and remove the carburetor.
  3. Disassemble the carburetor using a suitable screwdriver. Be cautious not to lose any small parts.
  4. Clean all components with carburetor cleaner and a soft-bristle brush.
  5. Reassemble the carburetor, ensuring all parts are in their correct positions.
  6. Reinstall the carburetor, and add fresh fuel to the tank before attempting to start the mower.

Checking The Ignition Coil

A faulty ignition coil may prevent your lawn mower from starting. To check the ignition coil:

  1. Disconnect the spark plug wire and remove the spark plug.
  2. Connect a spark plug tester to the spark plug wire.
  3. Pull the starter cord while observing the tester. A properly functioning coil should produce a spark.
  4. If there’s no spark, replace the ignition coil with a new one, and retest.

Inspecting The Flywheel

A damaged flywheel can affect the ignition system, hindering your lawn mower from starting. To inspect the flywheel:

  1. Remove the engine cover and the flywheel cover.
  2. Inspect the flywheel for any signs of damage or wear, such as missing or broken flywheel teeth.
  3. Use a flywheel puller to remove the flywheel if further inspection or replacement is required.
  4. If damaged, replace the flywheel with a new one before reassembling the engine.

By performing these advanced techniques, you can efficiently diagnose and address the issues that are causing your lawn mower not to start. Remember to consult the mower’s manual for specific information and requirements.

When To Seek Professional Help

There comes a time when troubleshooting a lawn mower that won’t start on your own can become more trouble than it’s worth. In such cases, it’s important to know when to seek professional help.

1. Persistent ignition issues: If you’ve checked and cleaned or replaced the spark plug, ensured there’s a proper fuel supply, and verified that the air filter isn’t clogged, but your lawn mower still won’t start, a professional can diagnose deeper issues with the ignition system.

2. Fuel system problems: Lawn mowers may have issues with their fuel systems, including clogged fuel lines or a dirty carburetor. If you’re not familiar with dismantling and cleaning these components, it’s better to consult a specialist who can perform the necessary maintenance and repairs.

3. Electrical issues on electric-start mowers: Electric-start lawn mowers may suffer from issues with batteries, wires, or solenoids. If you’re not confident in diagnosing or repairing electrical components, seeking professional assistance is a wise choice. They have the expertise and tools to handle such problems safely and efficiently.

4. Mechanical malfunctions: If your lawn mower shows signs of mechanical issues, such as unusual noises or vibrations when attempting to start, it might be the result of damaged or worn-out components. Professionals are experienced in identifying the root causes of such issues and can recommend or perform the necessary repairs or replacements.

5. Safety switch concerns: Modern lawn mowers come equipped with safety switches designed to prevent the machine from starting when certain conditions aren’t met. If you suspect a faulty safety switch may be preventing your mower from starting, consult with a professional to determine the issue and perform any required repairs.

In conclusion, taking matters into your own hands can undoubtedly be both cost-effective and satisfying, but recognizing when professional help is needed can save you time, money, and potentially costly mistakes. When in doubt, locate and consult an expert specialized in lawn mower repairs and maintenance.


In summary, a lawn mower may not start due to various reasons such as bad fuel, a dirty spark plug, a clogged air filter, a faulty fuel system, a dirty carburetor, a clogged fuel cap, or faulty safety switches. For electric-start models, there may be issues with the battery, loose or corroded wires, or a bad starter solenoid.

To resolve these issues, first check the fuel level and quality, ensuring that the mower has enough gas to run. If the fuel is old, consider draining and replacing it with fresh gasoline.

Next, inspect the spark plug for dirt or damage. Make sure that it is securely tightened and, if necessary, replace it with a new one. Examine the air filter for blockages or excessive dirt, cleaning or replacing it as needed.

Proceed to check the fuel system and carburetor for clogs or debris, cleaning them with a carburetor cleaner if required. Inspect the fuel cap for obstructions, ensuring that the air can flow properly. Lastly, examine the safety switches and electric components, tightening any loose connections and replacing faulty parts.

By addressing these common issues, lawn mower owners can increase the likelihood of their mower starting successfully, ensuring a well-maintained and neatly trimmed lawn. Remember to always consult the mower’s user manual and follow safety guidelines when performing maintenance and repairs.