Ignition System: Description and Operation

This ignition system features a universal distributor design, driven by the auxiliary shaft. The distributor is mounted on the left side of the engine, behind and below the power steering pump. The distributor has a die-case base which incorporates an integrally mounted TFI-IV ignition module and a Hall effect vane switch stator assembly. No distributor calibration is necessary and initial timing is not a normal adjustment.
On the XR4Ti, the universal distributor can be adjusted for octane needs by replacing the octane rod. The standard zero degree rod can be replaced with a three degree or six degree retard rod. Do not change timing by use of different octane rods without proper authority as federal emission requirements will be effected.
On all models, the TFI-IV module used features a ``push start'' mode. This allows ``push starting'' of vehicles with manual transmissions, if necessary.
The main function of the distributor is to direct high secondary voltage to the spark plugs. The distributor also supplies crankshaft position and frequency information to the ECA using a Profile Ignition Pick-up. The switch consists of a Hall effect device on one side and a magnet on the other. The rotary cup, which has windows and vanes, rotates and passes through the space between the Hall effect device and the magnet. When a window is between the Hall effect device and the magnet, the magnetic flux path is not completed from the magnet through the Hall effect device and back to the magnet. In this case, the switch is off and the Hall effect device sends no signal.
When a vane passes between the device and the magnet, the magnetic lines of flux increase. The flux lines are shunted through the vane back to the magnet, increasing the effect of the magnet on the Hall effect device and the devices turned on.
When the next window passes between the device and the magnet, the device is again shut down and the signal is turned off.
The voltage pulse is used by the EEC-IV system for sensing crankshaft position and computing the desired spark advance based on engine demand and calibration.