A faulty spark plug is a frequent reason an engine fails to start, making its removal a key skill. Knowing how to remove spark plug on lawn mower is essential for any homeowner who wants to perform basic maintenance. This guide provides clear, step-by-step instructions to help you complete this task safely and correctly.
You will learn the tools you need, the safety precautions to take, and the exact process for accessing, removing, and inspecting the plug. With a little patience, you can handle this job yourself and get your mower running smoothly again.
How To Remove Spark Plug On Lawn Mower
This section covers the complete removal process from start to finish. Before you begin, it’s crucial to ensure your mower’s engine is completely cool. Working on a hot engine is a major safety risk and can lead to burns.
Gather all your tools and materials beforehand. This preparation makes the job faster and prevents you from having to stop midway. Clear a flat, stable workspace where you can see what you’re doing.
Tools And Materials You Will Need
Having the right tools makes the job simple. You likely already have most of these items in your garage or toolbox. Here is what you need to collect:
- Spark Plug Socket Wrench: This is a deep socket, usually 13/16-inch or 5/8-inch, with a rubber insert to grip the plug. A standard socket will not work.
- Socket Wrench Extension (Optional but Helpful): Helps you reach plugs that are set deep in the engine shroud.
- Ratchet or T-Handle: To turn the spark plug socket.
- Spark Plug Gap Tool (Feeler Gauge): For checking and adjusting the gap on a new plug.
- Compressed Air or Small Brush: To clean debris from around the spark plug before removal.
- Safety Glasses: Always protect your eyes from falling debris.
- Gloves: Protect your hands from sharp edges and dirt.
- New Spark Plug (Recommended): It’s often best to install a new one. Ensure it matches your mower’s specifications.
- Anti-Seize Compound (Optional): A small amount can prevent the plug from seizing in the future.
Essential Safety Precautions
Safety must always come first when working with machinery. Ignoring these steps can lead to injury or damage to your mower. Follow these precautions carefully.
Disconnect the Spark Plug Wire
This is the most important step. Before touching anything, locate the spark plug wire—the thick rubber wire boot connected to the top of the plug. Firmly grasp the boot (not the wire itself) and pull it straight off. This prevents any accidental engine starts.
Ensure the Engine Is Cold
Never attempt to remove a spark plug immediately after running the mower. The engine and the plug itself can be extremely hot, causing severe burns. Wait at least 30 minutes to an hour to ensure everything has cooled down.
Work in a Well-Ventilated Area
If you’ve just run the mower, there may be gasoline fumes present. Perform the maintenance in an open garage or outdoors to ensure good airflow and reduce any fire hazard.
Step-By-Step Removal Process
Now that you’re prepared and safe, you can begin the actual removal. Follow these steps in order for a smooth process.
Step 1: Locate the Spark Plug
On most walk-behind lawn mowers, the spark plug is located on the side of the engine. It is covered by a removable rubber boot. On some riding mowers, you may need to lift or remove the engine cover or shroud to find it. Refer to your owner’s manual if you have trouble locating it.
Step 2: Clean the Surrounding Area
Use compressed air or a small brush to gently clear away any grass clippings, dirt, or debris from around the base of the spark plug. This prevents contaminants from falling into the engine cylinder when you remove the plug, which could cause serious damage.
Step 3: Remove the Spark Plug Wire Boot
As mentioned in the safety steps, firmly grip the rubber boot that is attached to the end of the spark plug. Twist it slightly back and forth while pulling straight up. Do not pull on the wire itself, as this can damage the connection inside the boot.
Step 4: Loosen the Spark Plug
Place your spark plug socket onto the plug’s hex nut. Attach your ratchet or T-handle. Turn the ratchet counter-clockwise (lefty-loosey) to break the plug free. It may be tight initially. Apply steady pressure to avoid stripping the plug or damaging the threads in the engine head.
Once the plug is loose, you can often finish unscrewing it by hand. Be careful, as the electrode end inside the engine may be covered in carbon or oil.
Step 5: Inspect the Old Spark Plug
Before you discard the old plug, take a moment to inspect it. Its condition can tell you a lot about your engine’s health. Look for the following signs:
- Normal Wear: The electrode will be worn down and the insulator may be light tan or gray in color.
- Carbon Fouled (Dry, Sooty Black): Indicates a rich fuel mixture, weak ignition, or dirty air filter.
- Oil Fouled (Wet, Black Deposits): Suggests oil is leaking into the combustion chamber, possibly from worn piston rings or valve guides.
- Overheated (White, Blistered Insulator): Means the plug is running too hot, which could be due to incorrect plug type, lean fuel mixture, or engine overheating.
Installing A New Spark Plug
While the primary focus is removal, installing the new plug correctly is just as important. Here’s a quick guide to ensure a proper installation.
Check and Gap the New Plug
Most new spark plugs come pre-gapped, but it’s wise to verify. Find the correct gap specification in your mower’s manual (common gaps are .028″ to .035″). Insert the feeler gauge between the center and side electrode. If adjustment is needed, gently bend the side electrode only.
Thread the Plug In By Hand
Carefully insert the new spark plug into the socket. Guide it into the spark plug hole and start threading it clockwise by hand. It should screw in smoothly and easily. If you encounter resistance, stop. You may have cross-threaded it, which can ruin the engine head. Remove it and start again carefully.
Tighten the Spark Plug
Once the plug is finger-tight, use your ratchet and socket to give it a final tighten. Do not overtighten. A good rule is to tighten it an additional 1/8 to 1/4 turn after it seats. If your plug has a crush washer, tighten until the washer compresses and the plug snugs up.
Reconnect the Spark Plug Wire
Finally, push the rubber boot firmly onto the end of the new spark plug until you feel or hear it click into place. Ensure the connection is secure so it won’t vibrate off during operation. Your maintenance is now complete.
Common Mistakes To Avoid
Even simple tasks can go wrong if you’re not careful. Avoid these common errors to ensure a successful spark plug change.
- Not Disconnecting the Wire First: This can lead to a dangerous shock or accidental engine cranking.
- Using the Wrong Socket: A standard socket can break the ceramic insulator. Always use a proper spark plug socket.
- Allowing Debris to Enter the Cylinder: Failing to clean the area can drop dirt into the engine, causing scoring and wear.
- Cross-Threading the New Plug: This strips the aluminum threads in the engine head, leading to costly repairs. Always start by hand.
- Overtightening: This can crack the plug’s insulator or damage the threads. Snug is sufficient.
- Forgetting to Reconnect the Wire: It sounds obvious, but it’s a frequent reason a mower won’t start after maintenance.
When To Call A Professional
While spark plug removal is generally straightforward, some situations warrant calling a small engine repair technician. If you encounter any of the following, it’s best to seek professional help.
- The spark plug is severely rusted or corroded in place and will not budge with reasonable force.
- The plug’s threads appear damaged or stripped when you remove it.
- The spark plug hole has visible damage or the plug seems to sit at an angle.
- You notice significant amounts of metal shavings or unusual debris on the old plug.
- The mower still won’t start after installing a correctly gapped new plug, indicating a deeper ignition or fuel system issue.
FAQ Section
Here are answers to some frequently asked questions about lawn mower spark plug removal and maintenance.
How Often Should I Remove and Check My Lawn Mower Spark Plug?
You should remove and inspect your spark plug at least once per mowing season, typically in the spring. For optimal performance, consider replacing it annually. If you use your mower extensively, check it more often.
What Size Socket Do I Need to Remove a Spark Plug?
The two most common sizes for lawn mower spark plugs are 13/16-inch and 5/8-inch. The best way to be sure is to check your owner’s manual or measure the hex nut on the old plug. A spark plug socket set often includes both sizes.
Can I Clean and Reuse an Old Spark Plug?
You can clean a lightly fouled plug with a wire brush and regap it, but replacement is usually recommended. Spark plugs are inexpensive, and a new one ensures reliable ignition. A worn or damaged plug should always be replaced.
Why Is My Spark Plug So Tight and Hard to Remove?
Spark plugs can seize due to heat cycles, corrosion, or carbon buildup. Ensure you’re using the correct socket and a proper length ratchet for leverage. Applying a penetrating oil like WD-40 around the base and letting it soak for 15 minutes can help loosen a stubborn plug.
What Should I Do If the Spark Plug Threads Are Damaged?
Do not force a new plug into damaged threads. This requires a repair called “heli-coiling,” where a technician installs a new threaded insert into the engine head. This is a job for a professional small engine mechanic.