Spark Plugs: Maintenance & Replacement

Before you have a fire, you need a spark! Internal combustion machines are little more than small, contained fires that are harnessed to turn a drive shaft. And the part that creates the spark is the all-important spark plug. The problem with spark plugs is that they can be disconnected, loose, dirty, or possibly defective.


Locating and Disconnecting the Spark Plug

You will find the spark plug located on the side of the engine, pointing sideways. The spark plug may not be immediately obvious because it is hidden by a protective rubber cap, and the cap itself is attached to the spark plug wire. The cap forms a 90-degree angle to keep the wire fitted close to the engine.

Grasp the rubber cap and pull it straight outward. This will release the cap and wire.

To remove the spark plug, use a spark plug wrench or deep socket (13/16 in. or 3/4 in.) attached to a ratchet wrench. Carefully turn the wrench counterclockwise. Do not force it or you may end up breaking off the spark plug.


Top 4 Spark Plug Problems and Solutions

Disconnected Wire: The plug wire may be visibly disconnected with the wire entirely loose and dangling onto the lawn-mower deck. Or the wire may be only slightly disconnected but the rubber cover makes it look as though it is still attached. The solution is to firmly push the wire back onto the spark plug.

Loose Plug: Over time, the spark plug itself (not the plug wire) may have worked its way outward, losing contact with the engine.This is easily solved by gently tightening the plug clockwise with the spark plug wrench or ratchet wrench.

Dirty: Dirt, oil, grass, and other forms of gunk may have infiltrated the spark plug, compromising its ability to spark. Instead of discarding the plug, it is possible to clean minor deposits. After disconnecting the spark plug wire, use a rag to clean the area around the spark plug – before removing the plug. This helps avoid getting debris in the combustion chamber when you remove the plug. Unscrew the plug. With a wire brush and spark plug cleaner, gently brush away any minor deposits.

Defective: Spark plugs eventually become so corroded that they must be replaced. Manufacturers recommended replacement every 100 hours. If the deposits on the spark plug do not easily brush away or the plug’s porcelain is cracked, it is time to throw away the plug and replace it.




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