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

The warm weather has arrived, and you’re ready to tackle your lawn. You pull the starter cord, but your lawn mower just sits there, silent. Frustration sets in – why won’t it start? This article will guide you through common reasons why your lawn mower may be refusing to cooperate, and offer troubleshooting tips to get you back to mowing in no time.


The most common causes of a lawn mower not starting are related to fuel, spark, or the engine itself. We’ll explore each of these areas, providing explanations and step-by-step instructions for resolving the issue. By following this guide, you’ll be equipped to diagnose and fix the problem yourself, saving you time and money.

Fuel Problems: When the Mower Can’t Get Gas

The first thing to suspect is whether the mower has access to fuel. If the fuel system is malfunctioning, the engine won’t be able to ignite. Here’s how to troubleshoot fuel-related issues:

1. Check the Fuel Level and Freshness

  • Check the tank: The most obvious culprit is an empty fuel tank. Fill it up with fresh gasoline.
  • Check for stale fuel: Even if you have fuel, it could be old and unusable. Gasoline deteriorates over time, losing its ability to ignite properly. If your fuel is more than a month old, it’s best to drain it and replace it with fresh gasoline.

2. Examine the Fuel Line and Filter

  • Inspect for kinks or blockages: The fuel line, which carries fuel from the tank to the carburetor, can become clogged or kinked. Look for any obstructions or bends in the fuel line.
  • Check the fuel filter: The fuel filter traps debris and prevents it from reaching the carburetor. If it’s dirty, it can restrict fuel flow. Replace it if it’s clogged.

3. Troubleshoot the Carburetor

  • Carburetor problems: The carburetor mixes fuel and air before sending it to the engine. If the carburetor is dirty, gummed up, or has a faulty float, it won’t be able to deliver the right mixture.
  • Cleaning the carburetor: Cleaning a carburetor requires removing it from the engine and using a carburetor cleaning kit. This is a more complex procedure, and it’s recommended to consult the owner’s manual or a repair guide for detailed instructions.

Spark Issues: When the Engine Can’t Ignite

If the fuel system is working, the next thing to consider is the spark. The spark plug is responsible for igniting the fuel-air mixture, and if it’s faulty, the engine won’t start.

1. Inspect the Spark Plug

  • Check for damage or wear: The spark plug can become worn, fouled, or damaged, preventing it from producing a spark. Examine the spark plug for any visible damage, such as cracked ceramic or a worn electrode.
  • Test the spark plug: Disconnect the spark plug wire from the plug. Then, hold the plug against a metal part of the engine block and pull the starter cord. You should see a blue spark. If not, the spark plug is faulty and needs replacing.

2. Check the Spark Plug Wire

  • Inspect for damage: The wire that connects the spark plug to the ignition coil can become damaged or corroded. Examine the wire for any cracks, breaks, or signs of corrosion.
  • Check for loose connections: Ensure that the wire is securely connected to both the spark plug and the ignition coil.

Engine Problems: When the Heart of the Mower Fails

Sometimes, the issue lies within the engine itself. These problems are often more complex to diagnose and require specialized knowledge.

1. Check the Air Filter

  • Clogged air filter: The air filter prevents dirt and debris from entering the engine. If it’s clogged, it restricts airflow and can cause starting problems. Inspect the filter and replace it if it’s dirty.

2. Inspect the Compression

  • Low compression: This indicates a problem with the piston rings, cylinder walls, or valves. Low compression prevents the engine from building up enough pressure to start. Testing compression requires a compression gauge, which is available at most auto parts stores.

3. Consider the Starter System

  • Faulty starter cord or recoil assembly: If the starter cord is broken or the recoil assembly is damaged, it won’t be able to crank the engine. You’ll need to replace these components.

Common Mistakes and Tips for Success

Here are some common mistakes people make when troubleshooting a lawn mower and helpful tips to make the process smoother:

  • Not reading the owner’s manual: The owner’s manual contains valuable information about your specific lawn mower, including troubleshooting steps and safety precautions.
  • Ignoring safety precautions: Always disconnect the spark plug wire before working on any electrical components. Wear eye protection and gloves when handling gasoline or cleaning parts.
  • Giving up too soon: Many lawn mower problems can be solved with a little patience and troubleshooting. Don’t give up until you’ve checked all the potential issues.

Getting Professional Help:

If you’ve gone through the troubleshooting steps and still can’t figure out why your lawn mower won’t start, it’s time to call in a professional. A qualified mechanic will have the tools and knowledge to diagnose and repair complex engine problems.


Now you’re equipped with the knowledge to troubleshoot a variety of lawn mower starting problems. By systematically checking the fuel system, spark system, and engine, you can often find and fix the issue yourself. Remember to always consult your owner’s manual and prioritize safety. With a little patience and know-how, you’ll be back to enjoying a perfectly manicured lawn in no time.


Why Won’t My Lawn Mower Start?

This is a common problem that can be caused by a variety of factors. The first step is to check the obvious – is there fuel in the tank? If so, then you’ll need to start troubleshooting the ignition system, the fuel system, or the engine itself. This article provides a comprehensive guide to help you diagnose the problem and get your mower running again.

What is the most common reason a lawnmower won’t start?

The most common reason a lawnmower won’t start is a lack of fuel. Make sure the fuel tank is full and that the fuel line is not clogged. If there is fuel in the tank, check the fuel filter and make sure it is not clogged.

How do I check the spark plug?

To check the spark plug, remove it from the engine and connect it to a spark plug tester. If the tester shows a spark, then the spark plug is working properly. If the spark plug is not working properly, you will need to replace it.

What if the spark plug is working but the engine still won’t start?

If the spark plug is working but the engine still won’t start, the problem may be with the fuel system. Check the fuel filter to make sure it is not clogged. If the fuel filter is clean, check the fuel lines to make sure they are not kinked or blocked.

What if the fuel system is working but the engine still won’t start?

If the fuel system is working and the spark plug is working, but the engine still won’t start, the problem may be with the engine itself. Check the carburetor to make sure it is not clogged. If the carburetor is clean, check the air filter to make sure it is not clogged.

What should I do if my lawnmower won’t start and it’s a brand new machine?

If you have a brand new lawnmower that won’t start, check the fuel tank to make sure it is full of fresh gasoline. You should also make sure the spark plug is properly connected and that the air filter is clean. If you have checked all of these things and your lawnmower still won’t start, you may need to contact the manufacturer for help.

What are some general troubleshooting tips for a lawnmower that won’t start?

Here are some general troubleshooting tips:
* Make sure the lawnmower has fuel, a spark, and air.
* Check the fuel filter, fuel lines, air filter, and spark plug.
* If you are still having trouble starting your lawnmower, you may need to take it to a qualified mechanic.

Leave a Comment