How a Pickup Coil in a Distributor Works

by Chris Gilliland


The distributor is an integral component of the ignition system, routing voltage from the ignition coil to fire the engine's spark plugs in sequence. The pickup coil determines this firing order as it spins within the distributor, using a magnetic sensor in place of mechanical breaker points.


The pickup coil consists of a hall effect sensor, which is housed within a metal rotor mounted on top of the distributor shaft. This shaft is spun by a gear that is driven by the camshaft. The rotor incorporates windows that open into a small gap between the rotor and a stationary permanent magnet. The number of windows correlates to the number of cylinders in the engine. As the rotor spins, the windows pass in front of the sensor, exposing it the magnet which triggers a signal to the car's ignition system which then fires a spark within the firing order.

The Hall Effect

The Hall effect is produced as an electrical current, or voltage, crosses a conductor. In terms of the pickup coil, the conductor is the sensor. The magnet within the rotor presents a current that is picked up by the sensor as the window passes by the sensor, which is then processed by the vehicle's ECU or ignition system.

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