Solved: Why Is My Lawn Mower Turning Over But Not Starting

A well-maintained lawn is a source of pride for many homeowners, and having a reliable lawn mower is essential to achieving that perfect look. However, even the most dependable lawn mower may occasionally refuse to start, leaving you with an overgrown mess. This article aims to provide a comprehensive guide to diagnosing and resolving the issue of a lawn mower that turns over but won’t start. By understanding the common reasons for this problem, you can quickly get back to maintaining your pristine lawn.

Common Reasons for Lawn Mowers Not Starting

There are several possible causes for a lawn mower not starting, and each category includes specific issues. Here is a list of the most common reasons and their corresponding problems:

A. Fuel-related Issues

  • Empty fuel tank: It may seem obvious, but checking the fuel level should be your first step. Running out of gas is a simple reason why your lawn mower might not start.
  • Stale fuel: Gasoline deteriorates over time, and stale fuel can cause your engine to struggle or not start at all. Make sure you use fresh fuel.
  • Clogged fuel lines: Dirt or debris in the fuel lines can prevent the flow of gasoline to the engine, causing starting difficulties.

B. Spark Plug Problems

  • Fouled spark plug: A dirty or fouled spark plug can prevent the engine from igniting the fuel properly. Cleaning or replacing the spark plug can resolve this issue.
  • Damaged spark plug: A damaged or worn-out spark plug won’t produce the necessary spark for ignition, resulting in starting problems.
  • Incorrect spark plug gap: The gap between the spark plug electrodes must be set to the correct specification for your lawn mower model. An incorrect gap can hinder the ignition process.

C. Airflow and Carburetor Issues

  • Dirty air filter: A clogged or dirty air filter restricts airflow into the engine, causing a fuel-rich mixture and starting difficulties. Cleaning or replacing the air filter can help.
  • Clogged carburetor: A clogged carburetor won’t provide the correct fuel-to-air mixture for combustion, resulting in starting issues.
  • Improperly adjusted carburetor: An incorrectly adjusted carburetor can cause starting problems and poor engine performance. Adjusting the carburetor to the correct settings can resolve these issues.

D. Battery and Electrical Issues

  • Dead battery: A dead or weak battery can cause problems with starting electric-start lawn mowers. Charging or replacing the battery may be necessary.
  • Loose or corroded connections: Poor electrical connections can prevent your lawn mower from starting. Check and clean any corroded connections and tighten any loose ones.
  • Faulty starter solenoid or switch: A malfunctioning starter solenoid or switch can prevent the engine from turning over. Replacing the faulty component can resolve the issue.

E. Mechanical Problems

  • Engine seizure: A seized engine, due to lack of oil or mechanical failure, will prevent the lawn mower from starting. In such cases, consult a professional for repair.
  • Damaged flywheel key: A damaged or sheared flywheel key will cause the engine to lose its timing, preventing it from starting.
  • Worn or damaged belts: Belts in a lawn mower can wear out or break, causing starting issues or poor performance. Inspect and replace damaged belts as needed.

Troubleshooting Guide

A. Identifying the Specific Issue

Determining the cause of your lawn mower’s starting problems is the first step in resolving the issue. The following step-by-step troubleshooting process will help you identify the specific problem:

B. Step-by-Step Troubleshooting Process

  1. Checking fuel system
    • Ensure there is sufficient fuel in the tank
    • Replace stale fuel with fresh fuel
    • Inspect and clean fuel lines, if necessary
  2. Inspecting spark plugs
    • Remove and examine the spark plug for signs of fouling or damage
    • Clean or replace the spark plug as needed
    • Check and adjust the spark plug gap according to the manufacturer’s specifications
  3. Examining airflow and carburetor
    • Inspect and clean or replace the air filter
    • Check the carburetor for clogs or debris and clean it, if necessary
    • Adjust the carburetor settings, if required
  4. Testing battery and electrical components
    • Check the battery voltage and charge or replace it if needed
    • Inspect electrical connections for looseness or corrosion and tighten or clean them as necessary
    • Test the starter solenoid or switch and replace any faulty components
  5. Investigating mechanical issues
    • Check for signs of engine seizure and consult a professional if necessary
    • Inspect the flywheel key for damage and replace it if required
    • Examine belts for wear or damage and replace them as needed

How to Fix the Problem

Once you have identified the cause of your lawn mower’s starting problems, you can move on to repairing or replacing the faulty components. Here are some tips for fixing issues in each category:

A. Repair or Replacement of Faulty Components

  • Fuel system: Replace fuel lines or filters if they are damaged or excessively clogged.
  • Spark plugs: Replace the spark plug if it is damaged or worn out.
  • Airflow and carburetor: Replace the air filter if it is damaged or excessively dirty. Rebuild or replace the carburetor if it is severely clogged or damaged.
  • Battery and electrical components: Replace the battery if it is dead or weak. Replace the starter solenoid or switch if they are faulty.
  • Mechanical components: Consult a professional for engine repairs or replacements. Replace damaged flywheel keys or belts.

B. Cleaning and Maintenance Tips

  • Fuel system: Regularly check fuel lines and filters for clogs or damage. Use a fuel stabilizer to prevent fuel from going stale.
  • Spark plugs: Clean the spark plug regularly and check the gap. Replace it every one or two seasons, depending on usage.
  • Airflow and carburetor: Clean the air filter regularly and replace it as needed. Keep the carburetor clean and adjusted properly.
  • Battery and electrical components: Ensure the battery is charged and properly maintained. Check electrical connections regularly for corrosion or looseness.
  • Mechanical components: Regularly inspect belts and other moving parts for wear or damage. Keep the engine well-lubricated and change the oil as needed.

C. When to Consult a Professional

Some lawn mower problems may be too complex or require specialized tools for a DIY repair. In these cases, it’s best to consult a professional lawn mower repair service to diagnose and fix the issue.

Preventive Measures

Taking preventive measures can help avoid lawn mower starting problems in the future. Follow these tips to keep your mower in top condition:

  • Maintain a regular maintenance schedule, including oil changes, filter replacements, and spark plug checks.
  • Store your lawn mower properly during the off-season, draining or stabilizing the fuel and removing the battery.
  • Use the right type of fuel, as specified by the manufacturer, to avoid issues with fuel quality.
  • Periodically inspect electrical and mechanical components for wear or damage, and address any issues promptly.


A lawn mower that turns over but won’t start can be frustrating, but by understanding the common causes and following the troubleshooting steps outlined in this guide, you can quickly identify and resolve the issue. Regular maintenance and proper storage techniques will help prevent future problems, ensuring that your lawn mower is always ready to keep your yard looking its best. Don’t hesitate to consult a professional lawn mower repair service if you encounter complex problems or require expert assistance. By taking care of your lawn mower, you can enjoy a beautiful, well-maintained lawn for years to come.


  • Nathan Collins

    Having spent years working in the landscaping industry, Nathan Collins has cultivated a wealth of knowledge about the natural world. He is committed to helping others appreciate the beauty in their backyards, whether it's through identifying rare rocks and minerals or crafting the perfect landscape.

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