SECTION 3 - CHASSIS & TURNTABLE
3120740
– JLG Lift –
3-107
CAMSHAFT POSITION (CMP) SENSOR
The CMP sensor uses a variable reactor sensor to detect cam-
shaft position. The CMP signal is created as piston #1 is a pre-
determined number of degrees after top dead center on the
power stroke.
CRANKSHAFT POSITION (CKP) SENSOR
The crankshaft position (CKP) sensor provides a signal used by
the engine control module (ECM) to calculate the ignition
sequence. The sensor initiates the reference pulses which the
ECM uses to calculate RPM and crank-shaft position.
ELECTRONIC IGNITION
The electronic ignition system controls fuel combustion by
providing a spark to ignite the compressed air/fuel w mixture
at the correct time. To provide optimum engine performance,
fuel economy, and control of exhaust emissions, the ECM con-
trols the spark advance of the ignition system. Electronic igni-
tion has the following advantages over a mechanical
distributor system:
• No moving parts
• Less maintenance
• Remote mounting capability
• No mechanical load on the engine
• More coil cooldown time between firing events
• Elimination of mechanical timing adjustments
• Increased available ignition coil saturation time
IGNITION COIL
The electronic ignition system uses a coil pack with one igni-
tion coil for each two cylinders in the engine. Each cylinder is
paired with its opposing cylinder in the firing order, so that
one cylinder on compression fires simultaneously with the
opposing cylinder on exhaust. The spark that occurs in the cyl-
inder on the exhaust stroke is referred to as a "waste spark."
The primary coils in the coil pack are triggered by the "Ignition
Coil Feed #1" and "Ignition Coil Feed #2" Signals from the ECM.
ENGINE CONTROL MODULE (ECM)
The ECM is responsible for maintaining proper spark and fuel
injection timing for all operating conditions. To provide opti-
mum operation and emissions, the ECM monitors the input
signals from the following components in order to calculate
spark timing:
• Engine coolant temperature (ECT) sensor
• Intake air temperature (IAT) sensor
• Throttle position sensor
• Crankshaft position sensor
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