Chrysler RAM TRUCK 2500 1994 Service Manual page 363

8D - 6 ' IGNITION SYSTEMS
COIL \
CONNECTOR
Fig. 12 Ignition Coil—5.91 ¥-8 HDC-Gas Engine
cylinder identification after receiving signals from
the crankshaft and camshaft position sensors.
Base i g n i t i o n t i m i n g is n o t adjustable o n any
engine. B y 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 i t
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 J L ¥-10 ENGINE
The ignition system used on the 8.0L V-10 engine
does not use a conventional mechanical distributor. I t
will be referred to as a Direct Ignition System (DIS)
or, distributor-less ignition system. Because of the
DIS, basic i g n i t i o n t i m i n g is n o t adjustable o n
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, i t
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
E N G I N E
C Y L I N D E R S
NUMBER
COIL
" M O U N T I N G 5
BOLTS (8)
J948D-6
Fig. 13 Ignition Coil Packs—8.0L ¥-10 Engine
REAR COIL PACK FRONT COIL PACK
RIGHT
IANK
LEFT
I A N K
FIRING ORDER
1-10-9-4-3-6-5-8-7-2
J 9 4 8 D - 1 2
Fig. 14 Spark Plug Cable Order—8.0L ¥-10 Engine
• Number 9 and 8
• Number 1 and 6
• Number 7 and 4
• Number 3 and 2
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-