The distributor cap is a device in the ignition system, which distributes electricity from the ignition coils to the spark plug wires at the proper time. It is usually made of hard plastic and a small amount of copper. Inside the distributor cap is the distributor rotor, which rotates as it receives current from the ignition coils and transmits it to the copper part of the cap, which then passes it on to the spark plugs.
The distributor rotor also has a metal component, which allows it to connect to the spark plug wires and cylinder wires in the engine. The rotor is mounted on the upper end of the distributor shaft, secured by two bolts to a plate on the top of the shaft. The rotor has built-in locators that fit snugly into holes in the plate so that it will not fall out. A centrifugal advance mechanism moves the rotor as the camshaft rotates.
The distributor cap is subjected to high voltage discharges all the time, therefore it must be inspected and replaced periodically. It is suggested to change it every two years or every 24,000 km of driving. Older vehicles are more prone to failures in this part.
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