Delphi Distributor Cap | DC20009

The distributor cap on your vehicle is used to distribute voltage from the ignition distributor, through the spark plug wires, to the spark plugs to create the spark needed for engine combustions. Electrical contacts for each spark plug wire on the inside of the distributor cap isolate and route voltage from the distributor to each spark plug wire independently. Some distributor caps also have an electrical connection for a wire from the ignition coil to send high voltage to the ignition distributor. Additionally, the distributor cap protects the internal parts of the ignition distributor, keeping out dirt and debris from the engine that could damage the ignition distributor. The distributor cap functions by having high voltage created by the ignition coil enter the ignition distributor which sends the voltage through a spinning rotor with an electrical contact that when comes into contact with the electrical contacts on the inside of the distributor cap, allows the voltage to flow to a spark plug wire.

Distributor cap contacts wear from the transfer of electricity jumping from the distributor rotor to the cap and from the cap to the spark plug wires. In addition, distributor caps are made from hard plastic which deteriorates from engine heat and becomes brittle overtime. Because of these things, distributor caps must be replaced regularly as part of routine maintenance.

Distributor caps should be replaced at the same time as spark plugs along with the distributor rotor and spark plug wires. Distributor cap replacement intervals vary based on manufacturer’s recommendations and range from 30,000 to 60,000 miles.

Distributor cap replacement is often very simple. By pulling off the spark plug wires on the top of the cap and either unclipping or unscrewing the distributor cap from the ignition distributor, the cap can be lifted off and replaced.

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