Description & Operation
See Figures 1 and 2
Taurus and Sable models equipped with the 2.5L, 3.0L, and 3.8L engines incorporate an ignition system using a Universal Distributor. The ignition system includes:
Some of the earlier models are equipped with a TFI-IV module. TFI stands for Thick Film Integrated and incorporates a molded thermoplastic module mounted on the distributor base. In later systems, the TFI-IV module's functions are carried out by the ignition control module.
In this system, the distributor is driven off the camshaft and uses no centrifugal or vacuum advance. The distributor operates by using a Hall effect vane switch assembly, causing the ignition coil to be switched on and off by the EEC-IV and TFI-IV modules on earlier vehicles, or the Powertrain Control Module (PCM) and the Ignition Control Module (ICM) on later vehicles.
The vane switch is an encapsulated package consisting of a Hall sensor on one side and a permanent magnet on the other side. A rotary vane cup, made of ferrous material, is used to trigger the signal OFF and ON. When the window of the vane cup is between the magnet and the Hall effect device, a magnetic flux field is completed from the magnet through the Hall effect device and back to the magnet. As the vane passes through this opening, the flux lines are shunted through the vane and back to the magnet. During this time, a voltage is produced as the vane passes through the opening. When the vane clears the opening, the window edge causes the signal to go to zero volts. The signal is then used by the EEC-IV or PCM (as applicable) for crankshaft position sensing and the computation of the desired spark advance based on engine demand and calibration. The voltage distribution is accomplished through a conventional rotor, cap and ignition wires.