What is the main function of spark plugs?

The main function of spark plugs is to ignite the air/fuel mixture inside the combustion chamber. This ignition process is critical for the operation of internal combustion engines, such as those found in small engines. When the engine cycle enters the compression stroke, the air/fuel mixture is compressed to a high pressure and temperature. The spark plug generates a high-voltage spark at just the right moment during this cycle, which ignites the compressed mixture. This combustion produces a rapidly expanding gas that drives the piston down, creating the power needed to turn the engine's crankshaft.

This ignition mechanism is essential for the effective functioning of the engine, as it initiates the power stroke. Without the spark plug's ability to create a spark, the engine would not be able to convert fuel into usable power, leading to failure in starting or running. Other options, such as regulating fuel flow or cooling the engine, are managed by different components within the engine system, making them unrelated to the specific role of spark plugs.