This lawn mower repair guide shows how to install a new spark plug on a lawn mower. The spark plug ignites the air and fuel mixture in the engine to start the lawn mower. If the engine runs rough or is hard to start, check the spark plug and replace it with the manufacturer-approved replacement part if the enamel body is cracked or the electrode is fouled with carbon or other buildup. Manufacturers recommend changing the spark plug when you tune up your lawn mower each year.
Use this procedure to replace the spark plug in Craftsman, Husqvarna, MTD, Murray, Poulan, Toro, Troybilt, Snapper and Weed Eater walk-behind lawn mowers.
Spark plug wrench
Spark plug gap tool
15 minutes or less
15 minutes or less
Replacing a spark plug on a lawn mower
This video explains how to replace a spark plug on a walk-behind lawn mower.
Disconnect spark plug wire
When the engine is cool, disconnect the spark plug wire from the spark plug.
Disconnect the spark plug.
Remove the spark plug
Use a spark plug wrench to loosen and remove the spark plug.
Remove the spark plug.
Gap the new spark plug
Use a spark plug gap tool to set the gap between the center electrode and the ground electrode. The gap specifications for your model are in the owners manual.
Gap the new spark plug.
Install the new plug
Thread the spark plug into the engine. Then tighten the spark plug with a spark plug wrench.
Install the new spark plug.
Reconnect spark plug wire
Reconnect the spark plug wire and start the mower to make sure it runs.
Warning: Undertaking repairs to appliances can be hazardous. Use the proper tools and safety equipment noted in the guide and follow all instructions. Do not proceed until you are confident that you understand all of the steps and are capable of completing the repair. Some repairs should only be performed by a qualified technician.