Dodge RAM TRUCK 1500 1995 Service Manual page 379

8D - 6 IGNITION SYSTEMS — ^ ^ — ^ — ^ _
B R
The ignition coil is not oil filled. The windings are
embedded in an epoxy compound. This provides heat
and vibration resistance that allows the ignition coil
to be mounted on the engine.
The automatic shutdown (ASD) relay, after receiv­
ing signals from the crankshaft and camshaft posi­
tion sensors, will supply battery voltage to the
ignition coil positive terminal. If these signals are not
received by the PCM after approximately one second
of engine cranking (start-up), the ASD relay will shut
off positive voltage to the coil. Coil operation (firing)
is then controlled by switching ground circuits (off-
and-on) through the PCM. The PCM will determine
cylinder identification after receiving signals from
the crankshaft and camshaft position sensors.
Base ignition timing is not adjustable on any
engine. By controlling the coil ground circuit, the
PCM is able to set the base timing and adjust the ig­
nition timing advance. This is done to meet changing
engine operating conditions.
The PCM adjusts ignition timing based on inputs it
receives from:
® The engine coolant temperature sensor
@ The crankshaft position sensor (engine speed)
• The manifold absolute pressure (MAP) sensor
• The throttle position sensor
• Transmission gear selection
For component testing, refer to the Diagnostics/Ser­
vice Procedures section of this group.
For removal and installation of this component, re­
fer to the Component Removal/Installation section of
this group.
IGNITION COIL PACKS—8.0L V-10 ENGINE
The ignition system used on the 8.0L V-10 engine
does not use a conventional mechanical distributor. It
will be referred to as a distributor-less ignition sys­
tem, ignition timing is n o t adjustable on any
8.0L V-10 engine.
Two separate coil packs containing a total of five
independent coils are attached to a common mount­
ing bracket located above the right engine valve
cover (Fig. 13). The coil packs are not oil filled. The
front coil pack contains three independent epoxy
filled coils. The rear coil pack contains two indepen­
dent epoxy filled coils.
When one of the 5 independent coils discharges, it
fires two paired cylinders at the same time (one cyl­
inder on compression stroke and the other cylinder
on exhaust stroke).
Coil firing (Fig. 14) is paired together on cylinders:
® Number 5 and 10
• Number 9 and 8
• Number 1 and 6
© Number 7 and 4
• Number 3 and 2
E N G I N E
-CYLINDER
NUMBER
BOLTS (8)
Fig, 13 ignition Coil Packs—8.0 L ¥-10 Engine
REAR COIL PACK FRONT COIL PACK
J948D-6
RIGHT
BANK
LEFT
BANK
FIRING ORDER
1-10-9-4-3-6-5-8-7-2
948D-12
Fig. 14 Spark Plug Cable Order—8. OL ¥-10 Engine
The ignition system is controlled by the powertrain
control module (PCM) on all engines (Fig. 15). The
PCM was formerly referred to as the SBEC or engine
controller.
The automatic shutdown (ASD) relay, after receiv­
ing signals from the crankshaft and camshaft posi­
tion sensors, will supply battery voltage to all of the
ignition coil positive terminals. If these signals are
not received by the PCM after approximately one sec­
ond of engine cranking (start-up), the ASD relay will