A spark plug wire delivers electricity to a spark plug in an engine. That electricity is used to create an electrical arc (the “spark”) that ignites a mixture of air and fuel that is injected into one of the engine’s cylinders. Each spark plug wire is connected on one end to a spark plug and on the other end to either an ignition coil or a distributor cap.
An internal combustion engine in a motor vehicle is made up of anywhere from four to eight (sometimes more) cylinders. Each cylinder houses a piston that moves up and down, pedaling the crankshaft the way your legs might pedal a bicycle. And each cylinder typically features one spark plug. When a spark plug fires and sets off a combustion event, it forces the piston down toward the crankshaft.
Many newer vehicles with “distributorless” ignition systems do not rely on spark plug wires. Instead, they have individual coil packs attached directly to each spark plug. But many vehicles do use spark plug wires, especially older models.
Spark plug wires are responsible for transferring a high voltage electrical signal to the spark plugs. That electricity creates an electrical arc that ignites compressed air and fuel. If a spark plug wire fails, you might notice one or more of the following symptoms:
To replace the spark plug wires, a technician will take the following steps: