The spark plug, which is a bit like an engine’s heartbeat, is the key component that lawn mowers use to ignite gasoline and produce power. Spark plugs, like a heartbeat, work hard and fire constantly to keep the engine running. They can wear down over time because of this. But luckily, figuring out how to replace a lawn mower spark plug isn’t anything like learning how to perform heart surgery. All you’ll need is a few simple tools and a bit of know-how to get this job done right.


Why you might need to change your spark plug

This is a component which will eventually need to be replaced, as we have already mentioned. Although the frequency at which a spark plug needs to be changed varies depending on the reason, there are some common symptoms (bad spark plug symptoms). The most typical reasons are: the spark plug has already been used for a season’s worth of time, oil or carbon has soiled it, or the mower has shown less power or fuel economy.


What you need to do to change your Lawn Mower Spark Plug

When actually considering how to change your lawn mower’s spark plug, you’ll probably want to figure out what tools you’ll need first. Though you don’t need a ton of tools for this job, it helps to have the right ones. These are the items you should have:

  • Socket wrench
  • Spark plug socket
  • Use a clean rag or a paper towel.
  • New spark plug
  • Insulated pliers are recommended

How to Remove a Lawn Mower spark plug + Replace

Now that you’ve got all of your tools together, let’s talk about how to change a lawn mower’s spark plug. Take your time to ensure the job goes smoothly.

1. Stage Lawn Mower

Before you get started, you’ll want to get your lawn mower positioned on a nice, flat, piece of ground. If you have a couple of pieces of scrap wood or small stones, it’s a good idea to block the wheels so that the mower won’t go rolling away.

Also, be sure that you’ve waited for the lawn mower’s engine to cool before you get going on this project. You’ll be working in very close proximity to the engine block and could easily burn yourself. I’d say to wait at least 30 minutes after using your mower before you get started.

2. Disconnect Ignition Cable

Now that your lawn mower is set in place you can locate the spark plug and disconnect the spark plug’s hood and wire that make up the ignition cable. This is something that you should do anytime you’re working on your lawn mower to prevent any chance of unexpected engine ignition.

To do this, I use a pair insulated needle-nosepliers to grab the hood at the center and gently lift it off of my spark plug. You won’t need to use much force to grab the spark plug hood because the pliers will grip the rubber pretty easily. If this isn’t your style, you can just grab the hood with your fingers and pull it off.

3. Remove the Old Spark Plug

Figuring out how to remove a lawn mower’s spark plug is arguably the most difficult part of the whole replacement process. Even though it can be annoying to remove the old plug, the right tools can make a big difference.


Grab my spark plug socket and put it on the wrench. Then, I place the spark plug in my hand. This way I can check that it’s making good contact with the spark plug and won’t strip.
Next, grab the socket wrench and attach it to your spark plug socket. Apply a little bit of counterclockwise (lefty loosey) pressure to the spark plug at first to be sure that the socket still won’t slip.

Slowly apply normal force until the threads become loose. Once the spark plug is loose, it’s easier to unscrew the remaining threads by hand because there will be no resistance and you’ll have a ton of spinning you’ll need to do.

4.  Examine the Old Plug

Before you dispose of your old sparkplug (which can be thrown in with regular garbage), make sure it is in good condition. Check for cracks, burns, and debris.

This step isn’t exactly necessary but I would definitely recommend it. It could be the key to determining why your spark plug failed.

It’s also really good to know what might’ve made your spark plug stop working in case it is anything other than the usual wear and tear. Cracked spark plugs, oily and sooty, can indicate other problems with your lawn mower, such as oil in your cylinder.

5. Clean and Install Spark Plugs

Once you have your new spark plug unboxed, make sure it’s clean, and also wipe out the top of the cylinder where the spark plug will screw in.

Now thread the new spark plug with your hand, until you feel resistance. Once you feel the resistance, grab your spark plug socket socket wrench and tighten the bolt. You’ll want to secure the spark plug relatively tightly but don’t overdo it.

6. Reconnect the cable

Before you put the spark plug cable hood and cable back together, ensure that the small metal terminal on the top of your spark plug is securely fastened. Hand-tight is fine, but it’s worth noting because sometimes these little pieces come loose.

All that’s left now is to reconnect the ignition cable as it was before. You should be able to feel the spark plug hood click into place as it slides over the spark plug’s terminal.

How to Remove a Lawn Mower’s Spark Plug Without a Socket (5 Techniques)

Although a specialized spark plug socket is the most common and recommended lawn mower spark plug removal tool, there are a few things you can do if you don’t have one handy. If you can, get a sparkplug socket. But if you’re in a pinch, and are wondering how to remove a lawn mower spark plug without a socket, here are some other methods you can try.

By Hand

You may have tried this already, but give your spark plug a firm twist with your fingers if you don’t have the right deep socket to use. Oftentimes spark plugs aren’t installed very tightly or may have loosened over time due to vibrations. If you’re lucky, you just might be able to unscrew your spark plug by hand.



The two most common tools that handymen and DIYers have are WD-40 (or another type of penetrating oils) and duct tape. One of these two items could be useful in most cases. Grab your lubricant now and see if it works.

Spray a small amount at the base of your spark plug if it won’t budge and then wait 5 minutes or so. Next, use your hand or rubber tubing to grip the spark plug and give the spark plug a twist. In some cases, this penetrating oils can make a huge difference.

Rubber Hose

A small length can be used to grip your spark plug and provide leverage. You can find a piece of rubber tubing that is approximately the same width as your spark plug or a little bit thinner. Slide it over the end and then twist.

Aluminum Foil Method

If you have deep sockets, but not the right size, this method might work for you. The idea is to use a larger socket and shim the inside with aluminum foil to grip the spark plug. I’ve never tried this but have heard of it working before.

Be careful not to pull the spark plug out or to shred any aluminum foil that might get into your cylinder.

Other Wrench and Pliers (Last Resort).

Well, I would never suggest doing this unless you have a pretty dire need to remove your spark plug right this instant, but you can try gripping the spark plug’s base with a set of pliers or a wrench that you have nearby.

This approach is not recommended and can often cause more harm than good. But, if you’re especially gentle, you may just wiggle it free. Instead of trying this, I suggest purchasing a spark plug socket.

How to Change a Spark Plug on a Riding Lawn Mower – Anything Different?

The process of changing a spark plug in a riding mower is the same as for a push mower. The difference is how you prepare for the spark plug removal.


If your riding mower has keyed ignition, make sure you turn it off and then remove the key. Then, disconnect the battery’s negative terminal and secure it away from the battery. This step is required for all riding mowers. It’s actually a good idea to disconnect the battery any time you do work on a riding mower. Follow the above steps and then reconnect the battery at last.

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