Q: How Does a Car’s Distributor Operate?

A distributor is a major ignition system component that every gasoline engine used for decades, and now almost no vehicles use. The distributor is linked to, and driven by the camshaft, and it rotates at exactly one half the speed of the crankshaft.

It performs two primary tasks. One function of the distributor is to accurately time the on-off control of the ignition coil primary winding by sending a signal to an ignition module. The distributor’s other main function is to receive high voltage current from the ignition coil secondary winding and send, or “distribute,” it to the correct spark plug at precisely the correct moment.

The distributor cap and rotor are replaceable maintenance items that contain electrical contacts which wear away due to transfer of the high voltage arc. Most distributors were adjustable so, by using a timing light, the ignition spark timing could be set correctly. Distributors were replaced by “distributorless ignition” systems using coil packs and crankshaft position sensors . Now, late model vehicles commonly utilize coil-on-plug ignition systems. These have one ignition coil per cylinder, are triggered by a crankshaft position sensor and are fully controlled by the powertrain control module.

If you run into problems with your distributor, have a certified technician diagnose your vehicle to find the right fix for your ignition system.