When the engine is running, high voltage created by the ignition coil travels to the ignition cap through the coil wire to the ignition rotor. As the ignition rotor turns in the distributor, the rotor distributes the spark by sending it in a synchronized order through the spark plug wires to the spark plug located in each of the engine's cylinders.
The distributor is a main component of the ignition system. It takes very high voltage and delivers it at exactly the right time to fire the spark plugs.
Depending on the type of system, the spark created by the ignition system ranges from 12,000 to 45,000 volts. This high voltage means 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.
To replace the ignition cap and rotor, also known as the distributor cap and rotor, the ignition wires are removed, along with the hardware securing the ignition cap to the distributor. When the cap is removed, the ignition rotor and distributor are inspected for wear. If needed, new parts are installed. Finally, the new cap is secured to the distributor and the ignition wires are reinstalled.
Having the cap and rotor inspected and/or replaced every 30,000 miles is a good way to avoid engine drivability problems.