JLG 660SJ Service Manual - Manual (Page 119)

SECTION 3 - CHASSIS & TURNTABLE
3121202 – JLG Lift – 3-69
IGNITION COIL
The electronic ignition system uses a coil pack with one
ignition coil for each two cylinders in the engine. Each cyl-
inder 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 cylinder 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/EPM.
ENGINE CONTROL MODULE/ENGINE
PERFORMANCE MODULE (ECM/EPM)
The ECM/EPM is responsible for maintaining proper spark
and fuel injection timing for all operating conditions. To
provide optimum operation and emissions, the ECM mon-
itors 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