Spark Plug Maintenance

Spark Plug Maintenance

How To Replace A Spark Plug On Your Mower

Dale, the Lawn Mower Expert
Lawn Mower Expert

A lawn mower is like a car. In order to keep running, it needs regular tune-ups.

Your lawn mower maintenance isn't complete after you've changed the oil and replaced the air filters. You also need to check your mower's spark plug.

A clean spark plug in good condition will ensure that your gas-powered mower has less trouble starting, even when it's starting cold. When your mower starts easily, you'll see all sorts of benefits:

  • Less engine wear
  • Improved fuel efficiency
  • Lower exhaust emissions

Many manufacturers and engine professionals suggest changing your spark plug every spring; always follow the recommendations in your mower's product manual.

However, if your mower is having trouble starting, you might find deposits and buildup on your spark plug that need to be cleaned.

Whether you're inspecting your old spark plug or installing a new one, below are the steps to follow to do it safely.

Spark Plug WrenchHow to Inspect an Existing Spark Plug

Before you buy a new spark plug, it makes sense to check the condition of the plug you already have. 

  1. Disconnect the spark plug lead.
  2. Clean the area around the spark plug to avoid getting debris in the combustion chamber when you remove the plug.
  3. Remove the spark plug using a spark plug wrench.
  4. Clean light deposits from the plug with a wire brush and spray-on plug cleaner. If necessary, use a sturdy knife to scrape off tough deposits. NOTE: Never clean a spark plug with a shot blaster or abrasives.
  5. Inspect the spark plug for the most serious signs of wear:
    • Stubborn deposits that can't be brushed away
    • Cracked porcelain
    • Electrodes that have been burned away 

If you notice any of those three signs of wear, it's time to replace your worn-out spark plug with a brand-new one.

Spark Plug LocationHow to Install a New Spark Plug

New engine parts can be a little intimidating to install the first time. However, after you've removed your old spark plug, it takes just a few simple steps to get your new plug in place.

  1. Use a spark plug gauge to measure the gap between the two electrodes (one straight, one curved) at the tip of your new spark plug. Many small engines require a .030" gap. Check the specifications for your model.
  2. If necessary, use a spark plug gauge to adjust the gap by gently bending the curved electrode. You'll know the gap is correct when the gauge drags slightly as you pull it through the gap.
  3. Insert the plug, taking care not to overtighten it (use a maximum of 15 foot-pounds of force).
  4. Reattach the spark plug lead.

The spark plug is one of the key components of your lawn mower's engine. Your gas-powered mower can't fire without it, and if it's damaged, you'll notice your mower's engine misfiring or taking a number of tries to start. 

A spark plug that's undamaged and free of deposits and buildup is just what you need to keep your mower running at peak performance.

NEXT: How to Prevent Fuel Problems with Your Lawn Mower
*Always use factory recommended parts to avoid discontinuing the warranty on the lawn mower.*

Dale, the Lawn Mower Expert
Lawn Mower Expert
Was this article helpful?