How to Change a Spark Plug in a Lawn Mower in 11 Steps

Like your yard needs frequent attention to maintain its beauty, your mower needs regular maintenance to carry on its top performance.

To ensure a machine that provides years of great service, knowing how to change a spark plug in a lawn mower is key.

In addition, it should help you save money on costly repairs and replacements throughout your mower’s life.

Ready to learn how to change your lawnmower spark plug? Let’s begin!

How to Change a Spark Plug in a Lawn Mower

You can perform most mower maintenance on your own, including the spark plug change.

What if you’re unsure how to take the spark plug wire off or if the plug needs replacing in the first place?

We have got you covered. We’ll explain the step by step instructions on replacing your lawnmower spark plugs at home.

Even beginners can do it with confidence because it is simple and uncomplicated.

Step #1: Pay attention to signs your spark plug needs changing

The lifespan of a spark plug is not indefinite. It deteriorates over time, affecting how smoothly the lawnmower engine operates.

If you want to prevent it, you must replace this part once every season or after 100 hours of use.

However, damage may require replacing the spark plug before the suggested interval.

How can you know when something is wrong?

The following are typical indications that you have a bad spark plug:

• Hard Start

The difficulty of starting a lawn mower is the most frequent symptom of a faulty spark plug.

A lawn tractor will not turn on when the key is turned, while a push mower may need more tries on the starter line before its engine revs to life.

The spark produced is not strong enough to ignite the gasoline and air combination that the carburetor has already supplied to the cylinder.

• Poor Engine Performance

If there is a problem with the spark plug, the engine might die out immediately after it starts.

Or, the engine might occasionally run a bit before stopping.

You may need to restart it after each failure, which can become increasingly challenging and annoying as the engine heats up.

Heat can produce expansion, which can widen the space between the firing electrodes and the core of the spark plug.

It also weakens the ignition spark in turn. An engine that misfires may splutter, miss, or pop due to a faulty spark plug.

• Excessive Fuel Consumption

The spark plug could be the issue if you are topping off your lawn mower’s petrol tank more frequently than usual during mowing or in between sessions.

Gasoline burns inefficiently when there is a poor spark. As a result, the mower’s fuel efficiency declines, and its fuel consumption rises.

Poor firing may also result from the raw gasoline smell while the mower is in use since the fuel might not be completely consumed.

• Changes in Physical Appearance

You can get further information on whether or not it’s necessary to update lawnmower spark plugs by how they look.

The top of their center electrodes ought to be flat. Replace the spark plug if the spark plug’s top is rounded.

Check the porcelain sheath of the spark plug for chips or cracks, and inspect the firing electrode for pitting.

Spark plug replacement is necessary if there is any damage to the plug.

It might only need a good scrubbing with a steel brush and distance correction between electrodes.

A spark plug could be black from carbon or from being soaked in gasoline, but it could still be capable of starting the motor.

Step #2: Purchase the right type of spark plug

Make sure you choose a spark plug appropriate for your mower because they are not all the same.

To find out which kinds your lawn mower can use, study your mower’s owner manual or look at the ceramic insulator on the plug, which typically has a number.

You can always take the plug out first and bring it to an auto parts store if you do not have a user manual or the number has worn off.

If the spark plug on your mower is missing, note the make and model of the engine and speak with the staff at a nearby auto parts store.

They ought to have no trouble locating suitable replacements.

Step #3: Position the lawn mower

Set your mower down on a sturdy, flat surface before you begin.

It would be ideal to use your porch or garage floor.

It allows complete engine control and protects you from getting hurt if the mower falls over while you’re conducting maintenance.

While doing this, you must also have the following:

• New spark plug
• Spark plug socket
• Depending on your machine, drive the socket wrench to 3/8 inches or 1/2 inches
• Screwdriver
• Spray-on cleaner
• Feeler gauge
• Sturdy knife
• Wire brush

Before working on the engine, ensure it is cold enough.

Give the mower at least 30 minutes to cool down after using it.

The metal components could burn you if you don’t let them cool down.

Step #4: Disconnect the spark plug lead 

If your lawnmower engine has a cover, remove it using a screwdriver.

Next, disconnect the ignition cable or spark plug lead.

This wire connects the distributor and socket connecting the voltage source, consequently supplying electricity.

For your protection, confirm that the connection has been cut off completely.

During this time, you must also inspect the ignition cable.

Wear brought on by time and use impacts the mower’s performance.

Check the wires for cracked or broken jackets; if you find any, it is time to replace them.

Step #5: Remove the spark plug

To loosen the plug, place it in the socket and crank counterclockwise.

Don’t force it if you are having difficulties ratcheting, as doing so could result in harm.

Apply lubricant instead, and let it sit for at least 10 to 15 minutes. The plug should then be easy to remove.

Since spark plug sockets are made especially to safeguard the ceramic insulator, you must use one when you use a spark plug.

A spark plug might be damaged if you try to remove it or put it in using the wrong tools.

Step #6: Clean and inspect the plug

Be careful when cleaning the plug with your wire brush and spray-on spark plug cleaner because it probably has buildup on it.

Remove any difficult deposits you come across using a knife.

Next, inspect the component.

You can reinstall the part if it is in good shape and still within the suggested use term.

Otherwise, you must get a new part if you see any scorched electrodes or a fractured ceramic.

Step #7: Adjust the gap using the spark plug gauge

The plug must have enough space before you can start the installation.

Using the spark plug gauge, determine the distance separating the straight and curved electrodes.

A minor adjustment should be necessary if you have the correct size for your machine’s make and model.

Carefully bend the curled electrode and the gauge in a small, precise motion to alter the gap.

Step #8: Install the new spark plug

Once the new plug is inserted, turn it clockwise manually.

Tighten further using the socket once the threads have hooked.

To avoid breaking the more fragile components, take care not to overtighten.

You must only ratchet the plug until it stops falling, then apply one more quarter turn to install it safely.

Step #9: Use a spark plug tester to inspect the spark plug

A quick and simple way to determine whether the spark plugs in your lawnmower are in fine order is to use a spark plug tester.

You can use any spark plug; you need to connect the tester to the item.

Step #10: Place the spark plug back in the lawn mower

The procedures are the same, whether replacing an old spark plug with a new one or putting the lawn mower’s old one back in.

This is also a perfect time to install a new cable if you have one.

Tighten the screws and replace the mower’s hood.

Make sure the threads are lined up with the socket.

You have managed to change your spark plug, so cheers!

Start the lawn mower’s engine to see if the spark plug is functioning properly.

It should not splutter, skip, or perform in any other way.

Step #11: Dispose of the damaged parts

You must now remove the old pieces you replaced completely and simply clean them.

Plugs can be safely disposed of in the trash, so feel free to do so.

You can also sell these pieces to a scrap yard to make extra money, assuming you already have some auto parts available.

Change Your Mower’s Spark Plug Without a Professional

Since you now know how to change a spark plug in a lawn mower, you can maintain your machine without needing to hire a professional.

You can now look forward to having additional cash, an effective mower, and a stunning lawn once you have this skill under your belt.