See Figure 1
The Thick Film Integrated (TFI-IV) ignition system is used for all EEC-IV electronic fuel-injected vehicles. The TFI-IV system module has six pins and uses an E-core ignition coil, named after the shape of the laminations making up the core.
There are two types of TFI-IV systems:
The TFI-IV ignition system with the Universal distributor has a distributor base mounted TFI ignition module and a Hall-effect stator assembly. The distributor also contains a provision to change the basic distributor calibration with the use of a replaceable retard (or octane) rod. The standard 0° calibration may be changed to either 3° or 6° retard rods. No other calibration changes are possible.
Initial timing adjustments are not required unless the distributor has been removed from the engine or moved from its initial factory setting.
Both the PUSH START and COMPUTER CONTROLLED DWELL TFI-IV systems operate in the same manner. The TFI-IV module supplies voltage to the Profile Ignition Pickup (PIP) sensor, which sends crankshaft position information to the TFI-IV module. The TFI-IV module then sends this information to the EEC-IV module which determines the spark timing. The EEC-IV module sends an electronic signal to the TFI-IV module to turn off the coil and produce a spark to fire the spark plug.
See Figures 2, 3 and 4
The operation of the universal distributor is accomplished through the Hall-effect stator assembly, causing the ignition coil to be switched off and on by the EEC-IV computer and TFI-IV modules. 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 armature, made of ferrous metal, is used to trigger the Hall-effect switch. When the window of the armature is between the magnet and the Hall-effect device, a magnetic flux field is completed through the Hall-effect device and back to the magnet. As the vane passes through the opening, the flux lines are shunted through the vane and back to the magnet. A voltage is produced while the vane passes through the opening. When the vane clears the opening, the window causes the signal to go to 0 volts. The signal is then used by the EEC-IV system for crankshaft-position sensing and the computation of the desired spark advance based on the engine demand and calibration. The voltage distribution is accomplished through a conventional rotor, cap and ignition wires.