Motor vehicles’ engines need an ignition system to ensure that a spark is given inside the combustion chamber at precisely the right moment.

All early motor vehicles and some recent ones have a distributor to manage the timing of the spark at each cylinder. The distributor is a bit like a middle-man that delivers a package from the suppliers to the consumers. Therefore, the distributor’s main job is to distribute the high voltage from the coil to the correct cylinder. This is done through the distributor cap and rotor. The high voltage travels along the coil which is connected to the rotor that is spinning inside the cap. As the tip of the rotor spins past a series of contacts, a high voltage pulse comes from the engine’s coil. The high voltage pulse travels across the gap between the rotor and contact, and then continues down the spark plug wire to the spark plug on the appropriate cylinder. At the spark plug, the high voltage pulse puts the spark into the plug and ignites the fuel mixture in the combustion chamber at the head of the cylinder. The resulting explosion turns the engine.

Obviously, the spark timing is so critical to an engine’s performance and this is why motor vehicles that contain a distributor need frequent tune-ups.

Most modern vehicles do away with the distributor. Instead, an engine control unit via an engine computer controls a transistor that opens and closes the high voltage current from the coil to the spark plug.

We hope that helps answer the question ‘What is What is a Distributor?’!

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