Distributors & Ignition Systems - MOTORCRAFT TFI Ignition System: Operation
Each time the teeth on the reluctor pass the teeth on the pick-up coil, the magnetic field around the pick-up coil builds and collapses. As this occurs, a pulse is generated in the pick-up coil and sent to the TFI ignition module. The ignition module then turns the ignition coil's primary circuit off and on causing a high voltage surge in the secondary which fires the spark plugs.