Spark Plug is installed inside the cylinder head to ignite the fuel/air mixture in the combustion chamber.
- The spark plug has a solid metal conductor called electrodes that are located and positioned to form a gap. This gap is between the insulated center electrode and the ground electrode. The spark jumps the gap to ignite the compressed air-fuel mixture in the engine cylinders.
- The spark plug has a metal outer shell enclosing a ceramic insulator. Centered in the insulator is the center electrode which carries the high voltage current from the ignition coil. A ground electrode attaches to the metal shell and is bent inward to produce the proper spark gap.
- Spark plugs may have a suppressor or resistance built into the center electrode. It reduces television and radio interference (static) caused by the ignition system. A spark plug may require gaskets when installed to assure a leakproof seal. Many engines use spark plugs with tapered seats which seal without a gasket. Some sparkplug threads are coated with an anti-seize compound which makes the plug removal easier, especially from aluminum cylinder heads
- Some engine have two spark plugs in each combustion chamber, Both plugs may fire together or one slightly ahead of the other. The additional plugs help reduce exhaust emissions and increase engine power