A spark plug, is a contraption for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine. This ignites the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine.
A plug has a metal threaded shell which is electrically isolated from a central electrode by a porcelain insulator. The central electrode, which sometimes contains a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The metal shell is screwed into the engine’s cylinder head, making it electrically grounded. The central electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell and designated the side, earth, or ground electrode. This can be seen in the diagram below.
They work by igniting the air/fuel mixture. Electrical energy is transmitted through the spark plug, jumping the gap in the plugs firing end if the voltage supplied to the plug is high enough. This electrical spark ignites the fuel/air mixture in the combustion chamber.
History of the Spark Plug
It was first credited to Etienne Lenoir in 1860 when he used an electric spark plug in his gas engine. Early patents for spark plugs included those by Nikola Tesla, Frederick Richard Simms and Robert Bosch. But only the invention of the first commercially viable high-voltage spark plug as part of a magneto-based ignition system by Robert Bosch’s engineer Gottlob Honold in 1902 made possible the development of the spark-ignition engine.
So When Was The Last Time You Changed Your Spark Plug?
They are similar to motor oil, fuel filters and air filters in that they require routine service and maintenance to keep your engine running strong. Common signs of faulty spark plugs include slow acceleration, loss of power, poor fuel economy, engine misfires, and difficulty starting the car. Without a spark, there would be no way for fuel to ignite in the combustion chamber.