When to Change Spark Plug on Lawn Mower?

Spark plugs are an essential part of the operation of a lawn mower engine and any vehicle. These parts allow the engine to start and you can begin mowing your lawn. Some novice users do not consider the fact that spark plugs have a certain life span and must be replaced at some point.

If your lawn mower takes a long time to start the engine and does not provide adequate power, it may be time to replace the spark plugs. Each of these parts enables combustion because they work together with the air/fuel mixture. That’s why they are an important part to check on your lawnmower.

So we’ve answered some of the most frequently asked questions about spark plugs, how long they last, symptoms of malfunction, and how to test each spark plug, among other important answers. So if you want to learn how to implement great maintenance on your lawn mower, we should start with the following question.

How Do I Know if my Spark Plug needs Changing?

There are some important considerations to keep in mind if you want to know exactly which spark plug needs to be replaced. Some factors are much more obvious than others in knowing if you should replace your lawn mower’s spark plugs. One of the main factors can come when your lawn mower won’t start at all.

The spark plugs include a special design set up to generate strong sparks that allow combustion within the carburetor. These spark plugs cause the air/fuel mixture to produce the power needed to run the mower. So when the spark plugs have deteriorated and are not working properly, it is not possible to get a proper start from the mower.

It may be that your lawnmower will still start even though the spark plugs are somewhat fouled and deteriorated. However, the mower will require a greater amount of effort and a higher voltage level for ignition. This also wears out the other parts of your lawnmower and that is why it is advisable to replace the spark plugs at the right time.

You also can check closely if a spark plug needs to be replaced. When the spark plugs have carbon residues or dirt on them, you should clean each of them to avoid deterioration at start-up. In case the spark plugs show signs of burning, this can also mean that there is damage. Here it may be necessary to replace each unit as the spark plugs have a certain service life.

When to Change Spark Plug on Lawn Mower?

Spark plugs on any engine should be replaced every so often, and the lawn mower is no exception. There are 2 main parameters to consider when changing each of your lawn mower’s spark plugs. One of the main considerations for knowing when to change the spark plugs is at the beginning of each season of the year.

This ensures that you have fresh spark plugs and an efficient engine throughout each season. Some people use their lawn mowers much more frequently than others. This may be due to the large areas of land that require more hours of work when using a lawn mower.

If this is the case for you and your mower then you should consider replacing spark plugs every 25 hours of use. In this case, this is an estimated amount of time as the spark plugs may last a little less or a little more than 25 hours. Most of the spark plugs that you can use in your lawnmower offer similar quality.

The life of the spark plugs is more dependent on the general maintenance you implement on your lawn mower. Part of this means cleaning the carburetor properly, replacing the engine oil, and replacing or cleaning the air filter, among other maintenance tasks. All of this can help extend the life of the spark plugs a little.

Also Read: Does Gas Go Bad in the Cold?

Lawn Mower Bad Spark Plug Symptoms

There are a few signs that are very important when a spark plug is not performing optimally. Here we have put together the bad symptoms that you might encounter that will indicate that it is time to replace faulty spark plugs. This is an important part of the maintenance you should carry out on your lawnmower.

  • Difficulty in starting: As mentioned above, difficulty in starting your lawn mower engine is one of the biggest problems that can occur. There is a possibility that the engine may start after several attempts or it may not start at all.
  • Engine failure: Another major problem that can occur with a lawn mower and many street vehicles is engine failure. This means that your lawn mower’s engine may be running erratically, which also presents itself as erratic power.
  • A short time of use: If the engine of your lawnmower has managed to start efficiently, it does not mean that there are no faulty spark plugs in the engine. This is because another problem is that the engine of your lawnmower stops a few minutes after starting.
  • Fuel economy: You need to use a certain amount of fuel for a certain amount of time of use of your lawnmower. When you need more and more fuel for the same amount of time of use as before, this can be another problem. Excessive fuel consumption is another bad symptom of deteriorated spark plugs.
  • Spark plugs showing signs of deterioration: Finally, you should also consider the appearance of the spark plugs after a visual inspection. You can look for signs of corrosion or damage across the entire surface of the spark plug. This is mainly due to rust or carbon build-up that needs to be cleaned from time to time.

Also Read: How Do You Stop a Zero-Turn Mower?

How Do I Know if my Lawn Mower Spark Plug is Bad?

The easiest way to detect if the spark plugs in your lawn mower are defective is to analyze the operation of the mower itself. If the mower that is running erratically, has a low power level or is difficult to start, this could mean that one or more spark plugs in the engine are faulty.

There are also other clear problems such as increased fuel consumption or an engine suddenly shutting down for no reason. When some of these symptoms occur you have the possibility to make a visual inspection of the spark plugs of your lawnmower. Most commonly you will notice signs of carbon or dirt build-up on one or more spark plugs.

This is easily remedied and only requires a thorough cleaning of your lawn mower’s spark plugs. Clear symptoms include difficulty in starting. Here the mower will need more time, more effort, and more voltage to be able to start the machine. There are even times when the engine does not start at all despite several attempts.

You can complete the spark plug check when replacing units that show signs of deterioration. Here the problem should be solved and the mower should run properly. It is also important to remember that this should be part of general maintenance to avoid other related problems.

How to Test a Spark Plug on a Lawn Mower?

To test the spark plug of a lawn mower it is important to know where it is located. To do this it may be important to read the owner’s manual as the location of the spark plug depends on the design of each mower. Once you have found the spark plug you should keep the tip where the spark is made in contact with some metal.

This will make it easier to see the spark that the spark plug can make when you try to start the engine of your lawn mower. If you cannot see any spark after trying to start the engine several times, the spark plug is defective. You will also be able to tell if it is a weak spark or a strong spark produced by the spark plug.

How Long Do Lawn Mower Spark Plugs Last?

Most spark plugs used in a lawn mower are rated for 25 to 30 hours of operating time. Some people believe that one set of spark plugs is sufficient for an entire season. However, the general maintenance of each mower must be taken into account.

The life of a spark plug can be shortened when a mower is not properly maintained. This can mean a clogged air filter, low or old engine oil, or spark plugs with dirt build-up that have not been cleaned.

How to Remove Spark Plug from Briggs and Stratton Lawn Mower?

You must first consider that the engine is cold and you must remove the boot covering the spark plug of your lawn mower. You need to use the right tool, such as a special spanner to remove the old spark plug.

Then you need to insert the new spark plug and do not over-tighten with the same spanner you have used before to avoid doing any damage to the new spark plug.


Replacing the spark plug of a lawn mower is important because it is part of the general maintenance of this machine. Also, remember to implement all the maintenance this machine needs to avoid the problems we have mentioned. This includes the engine oil, air filter, and other components that need to be checked and cleaned.

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Victoria Peterson

I am a passionate gardener who wants to help you create and maintain your dream yard. I know that it can be daunting to take on a project like this, but I am here to help. I have been gardening for years and have learned a lot along the way. I want to share my knowledge with you and help you create the perfect yard for your home.

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