The ignition coil generates the "spark" required to ignite gasoline. The ignition wire set (also know as the spark plug wires) conducts the spark generated by the ignition coil to the ignition distributor.
As the engine rotates, it operates the ignition distributor, synchronizing the delivery of the spark to the corresponding spark plug in each engine cylinder. The ignition wire set conducts the spark from the ignition cap to the spark plugs. To maintain synchronization, it is best to replace the spark plug wire set one wire at a time.
To replace a spark plug wire, the wire is removed from the distributor cap at one end and from the spark plug at the other end, then replaced.
Correct routing of the ignition wire set is critical to ensure that the spark plug wires don’t come into contact with rotating engine components or rest on the hot exhaust manifold.
Depending on what is required, the spark created by the ignition system ranges from 12,000 to 45,000 volts. Due to the high voltage, it’s critical that ignition system components are well insulated. If insulation breaks down, the spark never arrives at the spark plug, causing the engine to run poorly—or not at all.