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How to Tell if The Lawn Mower Spark Plug is Bad?

Is Your Lawn Mower Spark Plug Faulty? Here's How to Spot the Signs of a Bad Spark Plug

A lawnmower is a machine we often see cutting grass in parks, lawns, and other grassy areas. It has one or more revolving blades that cut the grass evenly and give it a nice clean look. It is used not only for cutting but also for trimming and chopping the grass in lawns, gardens, patches, and fields. The need for a lawnmower arose when people realized how difficult and time-consuming it is to manually chop the grass, especially in large areas of land such as golf courses, sports grounds, parks, and other areas where grass grows extensively.

So, they decided to hand over this job to a machine to do their work in less time with a neater finish. Thereupon, a lawnmower was designed. Even though Lawnmower has made our work a lot easier, it sometimes causes inconvenience. Sometimes it is due to a problem in a machine part, and other times our mishandling becomes the cause of machine injury. With we would look through the problems mostly reported by lawnmower users.

Lawn Mower Spark Plug Is Faulty: Possible Reasons

A faulty spark plug in a lawn mower can show several symptoms. Here are some examples of common symptoms:

How to Tell if The Lawn Mower Spark Plug is Bad

  • If the lawn mower is difficult to start, it could be due to a faulty spark plug. The engine may turn over, but it will not start.
  • A bad spark plug can cause the engine to misfire or sputter. This can cause a loss of power and a rough engine run.
  • A faulty spark plug can also result in poor engine performance. The lawn mower’s engine may struggle to maintain a constant speed, and it may not respond well to throttle inputs.
  • A faulty spark plug can cause the engine to burn more fuel than usual, resulting in lower fuel efficiency.
  • A bad spark plug may also show physical signs of damage or wear. The ceramic insulator on the plug may be cracked, the electrode may be worn down, or deposits or corrosion may have accumulated on the plug.

Explanation: How do Tell if The Lawn Mower Spark Plug is Bad?

The queries mostly reported are, ‘why is my lawnmower not starting?’, ‘how to tell if the lawn mower spark plug is bad?’, ‘why does my lawnmower keep shutting down?’ etc. Before getting into these questions, we must have enough knowledge about lawnmowers first because without knowing enough about the machine, we cannot understand the problems caused by it, let alone the solutions to these queries.How to Tell if The Lawn Mower Spark Plug is Bad

What Is A Spark Plug?

For your Lawnmower to work, you need to start it first but doing it without a spark plug is as impossible as cutting fire into steaks. Spark plus is a major component of a lawnmower as it ignites the fuel and air mixture inside of the cylinder of the mower’s engine. Combustion is triggered when the electricity jumps the gap at the tip of the mower’s plug. Thus, the spark plug provides the electric spark needed to ignite the fuel, making the mower work. But when their fuel combustion is incomplete, problems in the working and function of lawnmowers begin to arise.

Dirty and contaminated spark plugs are mostly the cause of your mower not getting started. Sometimes the plug gets loose after enough use, and as a result, the mower’s functions become inefficient. But when we get a new spark plug, we must make sure it’s the right one for our Lawnmower, but nowadays, companies focus on making such plugs that are interchangeable with different brands.

How To Tell If The Spark Plug Is Bad?

The Lawnmower has many parts, and sometimes it gets difficult to diagnose which part is causing the problem. Some parts of the Lawnmower are to last throughout the lifetime of the Lawnmower regardless of all the wear and tear, but a spark plug is not one of them. It needs proper maintenance, and it has to be replaced after a certain period if we want it to work efficiently.

We have some codes and keys to tell if the problem is in the spark plug. Listed below are some of them.

  • If the engine is turning over but the mower won't start, it's a sign that there might be an issue with the spark plug. Most probably, it is either dirt out or fouled.
  • If in the middle of mowing, your mower suddenly turns off, a spark plug might be to blame. Any damage to the spark plug would cause inconvenience and make the Lawnmower inefficient.
  • Thirdly the Lawnmower might be having issues with the spark plug if the gas in your fuel tank is running out faster than usual and you have to refill it again and again. This is because the defective spark might not be igniting all of the fuel and thus letting it out of the chamber without being utilized.
  • And lastly, if you have to pull with extra force and for longer than usual, this means that your spark plug is defective.

Why Do They Go Bad?

There are a lot of reasons as to why this might be happening, but the ones reported most often are:

  • There are electrodes present at the bottom that, with every use, get shorter and shorter to a point where they are no longer usable as they cannot spark the way it is required to let the engine run.
  • If the spark plug is not worn out but your mower is still not functioning properly, it indicates other factors malfunctioning the mower. These factors include overheating, carbon build-up around the plug, damaged protein sheath, or it might be due to the plug-top getting oil fouled.

Any of the above factors, if present, make the spark plug useless, and ultimately, it affects the efficiency of the mower.

How To Fix It?

It would help to get your plug checked annually for all these technicalities. Getting it serviced is one solution for this problem, but since it’s not so expensive, it is better to replace it. Once, long ago, spark plugs were expensive, and back then, people used to clean them for reusing the plug. Also, replacing the plug is not a difficult thing to do even if you are not into mechanics, you can still replace it in minutes. So, it’s better to replace it to prevent any further inconvenience for a considerable period.


If you notice any of these symptoms, you should inspect and replace the spark plug. For the correct spark plug type and gap for your lawn mower, follow the manufacturer’s recommendations, Check out the More Tools Cop on our Website.


Alan Murry

Alan Murray is the founder and chief editor of Toolscop.com, a leading online resource for household tools reviews and recommendations. With a passion for all things related to lawnmowers, grinders, compressors, and other essential tools for maintaining a beautiful and functional home, Alan has built a reputation as a trusted expert in the industry. As the chief editor of Toolscop.com, Alan oversees a team of dedicated writers and researchers who work tirelessly to provide readers with the latest information on the best household tools available on the market. Through his informative and engaging reviews, Alan offers readers valuable insights into the features, performance, and reliability of the tools he writes about. Alan's writing style is approachable, easy to understand, and always backed by thorough research and hands-on testing of the products he reviews. He takes pride in his work and is committed to providing his readers with accurate and honest assessments of the tools he covers. Whether you're a homeowner looking to upgrade your tool collection or a professional seeking the latest innovations in the industry, Toolscop.com offers a wealth of knowledge and expertise that can help you make informed decisions and get the most out of your household tools. With Alan's leadership and dedication to quality, Toolscop.com has become a go-to resource for anyone looking to make smart purchasing decisions for their home tools.

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