Engine System - LPG158Service Manual – CS7000Circuit DescriptionsIgnition SystemThe ignition system consists of a spark control module (aka Ignitor), three ignition coils, and a crank positionsensor. The crank position sensor reads a rotating 6 toothed ring which is mounted on the flywheel betweenthe flywheel and the engine.The heart of the system is the spark control module. It controls the current flow of each ignition coil primarycircuit in order to control when spark occurs based on inputs from the crank position sensor. Each coil firestwice per cylinder cycle. Once to initiate the power stroke and once in exhaust stroke (waste spark)The crank sensor is a two wire “ AC pulse generator”. It has a wire coil inside of it. As the toothed ringrotates, the teeth pass in line with the end of the sensor tip. This induces a voltage spike that the sparkcontrol module can “read” as cylinder position information. The number of spikes per minute is translated asengine RPM. One tooth on the ring is wider than the other five. This creates a unique “spike” so that thespark control module can distinguish the cylinders from one another. This allows it to fire the right ignitioncoil at the right time. Below is what the crank sensor wave form looks like on an oscilloscope. Notice thatevery sixth pattern is “wide”.Crank Position SensorSpark Control module Toothed Ring and flywheelIgnition CoilsWaveStar : Cougar Crank Sensor Waveform Page: 1
