Ignition System - DURA-Spark II: Operation: Notes
As the engine cranks, a reluctor (armature) on the distributor shaft rotates past a pick-up coil (stator). The reluctor has the same number of teeth as the engine has cylinders. As the teeth rotate past the pick-up coil, a signal is sent to the electronic control module.
From this signal, the module regulates current in the primary windings of the ignition coil. When current collapses in the primary, a high voltage surge occurs in the secondary windings of the ignition coil.
This high voltage is routed to the spark plugs through the rotor, distributor cap and spark plug wires.