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

How to Tell if The Lawn Mower Spark Plug is BadA 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 for machine injury. With we would look through the problems mostly reported by lawnmower users.

How to 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.

More About Lawnmower And Mowing?

Being the machine that made grass grooming a less hectic task, the Lawnmower is quite an impactful invention for this world. It is the secret recipe behind those lush green sports grounds and parks. Mowing is extremely necessary for lawn maintenance, and mowing properly gives turf the perfect trim and sheer lushness.

For mowing, you must know how to mow first. The height of your grass depends greatly on the frequency with which you mow it, and so does the thickness. Mowing makes grass denser and thicker because the mower cuts off the tip of the blades containing certain hormones that suppress the growth of your grass. But as we trim our turf, these blades cut off, resulting in dense and thicker growth.

For in-house lawns, homeowners recommend mowing the grass in an average time of 3-7 days, but the last time you mowed your grass does not determine whether it is time to mow or not. Some lawns require trimming every five days’ others don’t need it even after 3 to 4 weeks. Instead, the height and bushiness of your grass determine the right time the grass should be mowed. Grasses are typically mowed once a week to keep them tidy and trimmed in the growing season. But for healthy grass, frequent mowing is not recommended. Once in two weeks would do great.

However, if you sense the need for it earlier, getting it done causes no harm. But one must make sure not to cut it off more than one-third of the blade’s length. We must also ensure that our turf is getting the right amount of fuel, minerals, and nutrients. But if these blades get damaged, it might hinder photosynthesis, which would worsen your lawn’s condition, making it unhealthy and untidy.

Lawnmowers are typically classified into two broad types: rotatory mowers and reel mowers. The main difference is in their blade, where on the one hand, reel mowers cut the blades of grass with scissor-like action, the rotatory mowers, on the other hand, have one blade only. Besides that, one is good at trimming and leveling, while the other was designed with a niche of shortening the length. But the mower you go for depends on your budget, your law condition, turf condition, type of grass, and the area where the mower is to be used.

If we talk about the parts of a mower, the main parts are the starter handle, spark plug, mulcher door, muffler, air filter, gas cap, and safety shut-off lever. Now that we have enough know-how regarding the mower itself, we would dive into the discussion of what exactly is a spark plug? And how to tell if the lawnmower spark plus is bad?

What Is A Spark Plug?

For your Lawnmower to work, you need to start it first but doing it without a spark plus 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 one 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 running.
  • 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, the 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.


To finally conclude it all, we would state that a spark plug is an important part of the Lawnmower, so it needs to be checked quite often for any foulness or defect. If there is an issue with the spark plug, it directly affects the functioning of the Lawnmower. We can say the spark plug is bad if the mower keeps on shutting down if we can’t get the engine started if it takes more than normal time and energy to kick start it, and if the gas runs out faster than usual. And lastly, to get this problem fixed, you need to replace your spark plug with a new one suitable for your specific mower.

Check out the More Lawn Mower Tools from our Website.

Tom Hanks

Tom Hanks is a DIY lover and an expert of tools to give you detailed unbiased reviews and guides on using and buying great tools for your DIY projects.

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