Ignition System - TFI-IV: Operation
When a window is between sending unit and magnet, magnetic circuit is incomplete. In this case, system is off and sending unit sends no ignition signal. When a vane passes between sending unit and magnet, magnetic lines of flux are created between sending unit and magnet. The system is turned on.
When next window passes between sending unit and magnet, the sending unit is again shut down and the ignition signal is turned off. These voltage pulses are used by the EEC-IV system for sensing crankshaft position and computing desired spark advance.