The spark plug is most closely associated with which system?

The spark plug is most closely associated with the secondary system because it plays a crucial role in the ignition process that ignites the air-fuel mixture in an internal combustion engine. The secondary system refers to components involved in igniting that mixture, including the ignition coil and the spark plug itself.

In the context of an outdoor power equipment engine, the ignition system is responsible for generating the spark necessary for combustion. The spark plug receives voltage from the ignition coil and generates a spark at the right moment in the engine cycle to ignite the fuel mix, thereby driving the engine’s power cycle.

Understanding the function of the spark plug emphasizes its importance in the combustion process, distinguishing it from primary components, which may include the battery or other initial power sources. The spark plug's role as part of the secondary system highlights its specific contribution to the engine's operation.