System Operation - Ford Ranger Maintaince And Repair Manual

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View of the TFI−IV ignition system components
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SYSTEM OPERATION

The CMP sensor, housed inside the distributor, responds to a rotating metallic shutter mounted on the
distributor shaft. This rotating shutter produces a digital Profile Ignition Pick−up (PIP) signal, which is used
by the PCM and ICM to provide base timing information, determine engine speed (rpm) and crankshaft
position. The distributor shaft rotates at one−half crankshaft speed, therefore the shutter rotates once for every
two crankshaft revolutions.
The ICM functions in either one of two modes: push start or Computer Controlled Dwell (CCD). The push
start mode allows for increased dwell, or coil on time, when starting the engine. During this mode, the ICM
determines when to turn on the ignition coil based on engine speed information. The coil is turned off, thereby
firing, whenever a rising edge of a SPark OUTput (SPOUT) signal is received. The SPOUT signal is
generated by the PCM, and provides spark timing information to the ICM. During the push start mode, the
SPOUT signal only indicates the timing for coil firing; the falling edge of the SPOUT signal is ignored.
Despite the name, the push start mode is also enabled during engine starting with the ignition key.
Do not attempt to push start a vehicle equipped with an automatic transmission.
The rotary armature has open areas called windows and tabs called vanes
The vane interrupts the magnetic field passing through the Hall effect device
170 General Information