Good insulation to prevent leakage or short circuit of high voltage current and ensure smooth transfer of current to the spark plug.
Can prevent dust, moisture, etc. from entering the spark plug, avoiding corrosion or short circuit, prolonging the life of the spark plug.
Some of the spark plug caps have built-in resistors, which can reduce the electromagnetic interference generated during ignition and protect the vehicle's electronic equipment.
The spark plug cap transfers the high voltage generated by the ignition coil to the spark plug to ensure that the ignition system works properly.