Spark plugs are installed on the side or top of the engine. In the early days, spark plugs were connected to the power distributor through cylinder wires. In the past decade, engines in small cars have mostly been changed to have ignition coils directly connected to spark plugs. The working voltage of the spark plug is at least 10000V, and the high-voltage electricity is generated by the ignition coil from 12V electricity, which is then transmitted to the spark plug.

Spark plugs are important components of the ignition system in gasoline engines. They can introduce high-voltage electricity into the combustion chamber and cause it to jump over the electrode gap to generate sparks, thereby igniting the combustible mixture in the cylinder. It mainly consists of wiring nuts, insulators, wiring screws, central electrodes, side electrodes, and the shell, with the side electrodes welded to the shell.