Red Seal Agricultural Equipment Technician Practice Exam

What is the primary function of a spark plug in an engine?

1. To cool the engine

2. To ignite the air-fuel mixture

3. To filter engine oil

4. To measure engine temperature

The correct answer is: To ignite the air-fuel mixture

The primary function of a spark plug in an engine is to ignite the air-fuel mixture within the combustion chamber. When the engine is operating, the air-fuel mixture is compressed, and the spark plug generates a high-voltage spark at the right moment in the engine cycle. This spark ignites the compressed mixture, resulting in a controlled explosion that pushes the piston down, ultimately generating power for the engine. The accurate functioning of the spark plug is crucial for engine performance, efficiency, and emissions control. A faulty spark plug can lead to misfires, rough idling, and poor fuel economy, highlighting its essential role in the combustion process. Factors such as the spark plug's gap, condition, and the timing of the spark are all vital to ensure optimal engine performance. The other functions mentioned, such as cooling the engine, filtering engine oil, or measuring engine temperature, are handled by different components within the engine system, such as the radiator, oil filter, and temperature sensors, respectively. Each of these parts has distinct responsibilities that contribute to the overall operation of the engine, but they do not involve the ignition of the air-fuel mixture, which is why the correct answer is centered around the spark plug's primary role.