Lawn Mower Spark Plugs Explained

If you are like most people, when you think of spark plugs, you initially think about the auto parts in your car or truck’s engine. However, any vehicle with an internal combustion engine likely has spark plugs in it. This includes your lawn mower. Understanding the role of spark plugs and how they work in a lawn mower can help you take better care of your equipment.

What Do Spark Plugs Do?

In a gasoline engine, there are cylinders with pistons in them. The engine creates power by moving those pistons up and down and turning a crankshaft. As you likely know, the pistons are moving by igniting a mixture of gasoline and air. That is where the spark plugs come into play. They ignite the fuel/air mixture in the cylinders to make power.

Are Lawn Mower Spark Plugs Different?

The spark plugs in small engines such as lawn mowers are more or less the same as the spark plugs in your car or truck. Typically, you will have far few of them (small engines often only have one, maybe two cylinders).

However, a spark plug on a lawn mower is usually a little smaller. Most notably, it likely has smaller threads. These differences are fairly minor (about 2 millimeters in size). Nonetheless, they usually aren’t interchangeable. Although, some lawn mowers are designed to use auto spark plugs.

Changing Lawn Mower Spark Plugs

Check your spark plugs annually and consider changing them if your lawn mower is running strangely. For example, you may experience a major drop in fuel efficiency if the spark plug is bad. You may also have a hard time starting the engine or it may shut off without warning.

In some cases, the problem with a spark plug is that it has been fouled from use. You can clean these with a wire brush and/or purpose-made cleaner. Simply replace the plug once it is clean.

If the problem is more severe or the plug is physically damaged, replace it with a new one. Check your owner’s manual or the number on the current spark plug to determine what the right replacement type is.

Remove the spark plug wire and loosen the spark plug slowly with a socket wrench. Make sure to use a spark plug socket and be gentle. If it doesn’t come out easily, use some lubricant and try again.

Adjust the gap between the curved and straight electrodes to match the old plug. Then, put the new spark plug back in its place and tighten carefully with your socket wrench. Finally, reconnect the spark plug wire. Once you are done, you can clean up and check that your lawn mower starts easily again.

Get Started

Taking care of your lawn mower is easy. Whether it needs a tune-up or is having problems starting, get started changing your spark plugs. Anyone can learn to perform basic maintenance tasks like this. Better yet, it can save you significant money when you do it yourself. Head to your local auto parts store to find the right tools and parts.