Spark Plug: Description and Operation

SPARK PLUG

DESCRIPTION

Gasoline engine has been equipped with the spark plugs which are manufactured by NGK or CHAMPION.

The spark plugs have an internal resistance to reduce noise when fuel is ignited and there are two types of internal resistances. NGK spark plugs have only carbon glass type of internal resistance, but CHAMPION spark plugs have two different types of internal resistances, cartridge type of internal resistance or carbon glass type of internal resistance, depending on model and engine.

The color of terminal stud can discriminate the CHAMPION spark plugs with cartridge type of internal resistance from the CHAMPION spark plugs with carbon glass type of internal resistance. The CHAMPION spark plug with cartridge type of internal resistance has a silver terminal stud and the CHAMPION spark plug with carbon glass type of internal resistance has a dark gray terminal stud.

Carbon glass type of internal resistance may be measured with a 12 V Multi-Tester, but the internal resistance measurement must not be used as a way to inspect the spark plug because accurate measurement of the internal resistance is not possible Although the measured internal resistance value is not within specification, 3-10 Kohms , do not replace the spark plug.

Cartridge type of internal resistance can not be measured with a 12 V Multi-Tester. If measuring the internal resistance with a 12 V Multi-Tester, the tester may show a reading much higher than the actual resistance value because both ends of the cartridge type of internal resistance are very rough. If you insist on measuring the cartridge type of internal resistance, a 1000 V Mega-Ohmmeter should be used. However, like the carbon glass type of internal resistance, the internal resistance measurement must not be used as a way to inspect the spark plug because accurate measurement of the internal resistance is not possible. Although the measured internal resistance value is not within specification, 5-15 Kohms , do not replace the spark plug.

Spark plugs replacement frequently occurred in repair shops when a vehicle exhibited engine misfiring, rough idling, etc. because the spark plug internal resistance is measured in most of the repair shops as a way for spark plug inspection. However, accurate measurement of spark plug internal resistance is not possible as mentioned above and we could not generally find any defects in the collected inferior spark plugs.