What is the Function of a Spark Plug in an Engine
In an internal combustion engine, thespark plugis what gets it all started. Many devices and vehicles use internal combustion engines, from cars and trucks to power lawn equipment like chainsaws and snowblowers. Internal combustion engines use fuel, air, and fire to produce mechanical energy.The spark plug does exactly what it sounds like it should do: it creates a spark. Its sole function is to generate one tiny spark, and that spark ignites the mixture of fuel and air that's been compressed inside the engine. The fuel and air igniting is what powers the engine.Internal combustion engines come in two basic styles: two-cycle or four-cycle. The two types have their distinct differences, but in both types, each time the piston makes an upstroke and compresses the fuel and air mixture inside the cylinder, the spark plug creates a spark and ignites the mixture. So a car that is running at 3000 rpm, for example, will be creating many thousands of sparks per second. Spark plugs definitely have their work cut out for them.Small engines, like those used in push lawn mowers, only require one spark plug. But larger engines require many more; a car or truck could easily have six or eight spark plugs. Different kinds of engines require different spark plugs, so a plug that works in one engine may not necessarily work in another. Each engine has its own spark plug specifications, which you can typically find in the equipment's owner manual or service manual.The spark plug receives an electrical signal, coming from the spark plug wire, that tells it when to fire. It uses voltage between its two electrodes - separated by a precisely-tuned gap - to create the spark that ignites the fuel and air. If the side electrode is bent (the one that sticks out at the bottom in an "L" shape) it will change the measurement of the gap, and it could prevent the spark plug from firing. Similarly, if the spark plug is worn down or dirty, it also might not be able to create the necessary spark.Spark plugs on power equipment like lawn mowers can be replaced fairly easily, and your mechanic will check or replace your vehicle's spark plugs when he does a tune-up. Instead of replacing a spark plug, you can often clean it or re-gap it, and get more use out of it before you need to replace it. An average spark plug will typically cost somewhere around $4 or $5, but performance or high-end spark plugs can easily cost much more.
