What is the primary function of the spark plug in an ignition system?

The primary function of the spark plug in an ignition system is to ignite the air-fuel mixture within the combustion chamber of the engine. This ignition occurs when the spark plug generates a high-voltage spark that jumps across a gap between its electrodes. The spark must occur at a precise moment in the engine cycle, just as the piston reaches the top of its compression stroke, to ensure efficient combustion. Once ignited, the air-fuel mixture burns rapidly, producing the energy required to power the engine.

While the spark plug does create a high voltage necessary for producing the spark, its main purpose centers around starting the combustion process itself. Other functions referenced in the options, such as managing fuel injection timing or monitoring engine temperature, are handled by different components in the vehicle's systems and are not the functions of the spark plug. Therefore, understanding that the spark plug's essential role is direct ignition clarifies why it is crucial for engine performance.