
TIMING BELT/CHAIN AND
SPROCKETS
REMOVAL
(1) Disconnect battery negative cable.
(2) Remove Timing Chain Cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(3) Re-install the vibration damper bolt finger
tight. Using a suitable socket and breaker bar, rotate
the crankshaft to align timing marks as shown in
(Fig. 73).
(4) Remove camshaft sprocket attaching bolt and
remove timing chain with crankshaft and camshaft
sprockets.
INSPECTIONÐMEASURING TIMING CHAIN
STRETCH
(1) Place a scale next to the timing chain so that
any movement of the chain may be measured.
(2) Place a torque wrench and socket over cam-
shaft sprocket attaching bolt. Apply torque in the
direction of crankshaft rotation to take up slack; 41
N´m (30 ft. lbs.) torque with cylinder head installed
or 20 N´m (15 ft. lbs.) torque with cylinder head
removed. With a torque applied to the camshaft
sprocket bolt, crankshaft should not be permitted to
move. It may be necessary to block the crankshaft to
prevent rotation.
(3) Hold a scale with dimensional reading even
with the edge of a chain link. With cylinder heads
installed, apply 14 N´m (30 ft. lbs.) torque in the
reverse direction. With the cylinder heads removed,
apply 20 N´m (15 ft. lbs.) torque in the reverse direc-
tion. Note the amount of chain movement (Fig. 74).
(4) Install a new timing chain, if its movement
exceeds 3.175 mm (1/8 inch).
INSTALLATION
(1) Place both camshaft sprocket and crankshaft
sprocket on the bench with timing marks on exact
imaginary center line through both camshaft and
crankshaft bores.
(2) Place timing chain around both sprockets.
(3) Turn crankshaft and camshaft to line up with
keyway location in crankshaft sprocket and in cam-
shaft sprocket.
(4) Lift sprockets and chain (keep sprockets tight
against the chain in position as described).
(5) Slide both sprockets evenly over their respec-
tive shafts and use a straightedge to check alignment
of timing marks (Fig. 75).
(6) Install the camshaft bolt. Tighten the bolt to 68
N´m (50 ft. lbs.) torque.
(7) Check camshaft end play. The end play should
be 0.051-0.152 mm (0.002-0.006 inch) with a new
thrust plate and up to 0.254 mm (0.010 inch) with a
used thrust plate. If not within these limits install a
new thrust plate.
(8) Install the timing chain cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).
Fig. 73 Alignment of Timing Marks
1 - TIMING MARKS
Fig. 74 Measuring Timing Chain Stretch
1 - TORQUE WRENCH
2 - 3.175 MM (0.125 IN.)
Fig. 75 Alignment of Timing Marks
1 - TIMING MARKS
9 - 170 ENGINE 5.9LBR/BE

(2) Using recommended tool 8544 Camshaft Bush-
ing Remover Installer, Drive out bearing shells.
REMOVALÐCAMSHAFT
(1) Remove rocker arms and push rods (Refer to 9
- ENGINE/CYLINDER HEAD/ROCKER ARM /
ADJUSTER ASSY - REMOVAL). Identify each part
so it can be installed in its original location.
NOTE: The 4 corner tappets can not be removed
without removing the cylinder heads and gaskets.
However, they can be lifted and retained for cam-
shaft removal.
(2) Remove the Bolts retaining the yoke retaining
spider. Remove the yoke retaining spider, tappet
aligning yokes and tappets.
(3) Remove upper and lower intake manifolds
(Refer to 9 - ENGINE/MANIFOLDS/INTAKE MANI-
FOLD - REMOVAL).
(4) Remove timing chain cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL) and timing chain and
sprockets (Refer to 9 - ENGINE/VALVE TIMING/
TIMING BELT/CHAIN AND SPROCKETS -
REMOVAL).
(5) Remove camshaft thrust plate (Fig. 27).
(6) Install a long bolt into front of camshaft to aid
in removal of the camshaft. Remove camshaft, being
careful not to damage cam bearings with the cam
lobes.
INSTALLATIONÐCAMSHAFT BEARINGS
(1) Install new camshaft bearings using recom-
mended Tool 8544 Camshaft Bushing Remover
Installer, by sliding the new camshaft bearing shell
over proper adapter.
(2) Bearings must be carefully aligned to bring oil
holes into full register with oil passages from the
main bearing. If the camshaft bearing shell oil holesare not in exact alignment, remove and install them
correctly. Install a new core hole plug at the rear of
camshaft.Be sure this plug does not leak.
INSTALLATIONÐCAMSHAFT
(1) Lubricate camshaft lobes and camshaft bearing
journals. Using a long bolt, insert the camshaft into
the cylinder block.
NOTE: Whenever an engine has been rebuilt, a new
camshaft and/or new tappets installed, add 1 pint of
MoparTCrankcase Conditioner, or equivalent. The
oil mixture should be left in engine for a minimum
of 805 km (500 miles). Drain at the next normal oil
change.
(2) Install camshaft thrust plate. Tighten the torx
bolts to 22 N´m (16 ft. lbs.) torque.
(3) Check camshaft end play. The end play should
be 0.051-0.152 mm (0.002-0.006 inch) with a new
thrust plate and up to 0.254 mm (0.010 inch) with a
used thrust plate. If not within these limits install a
new thrust plate.
(4) Line up key with keyway in sprocket, then
using Special Tools C-3688, C-3718 and MB990799
install crankshaft timing sprocket. Make sure the
sprocket seats against the crankshaft shoulder (Fig.
28).
Fig. 27 Camshaft
1 - CAMSHAFT
2 - THRUST PLATE
Fig. 28 Crankshaft Sprocket Installation
1 - SPECIAL TOOL C-3688
2 - SPECIAL TOOL C-3718
3 - SPECIAL TOOL MD990799
BR/BEENGINE 8.0L 9 - 201
CAMSHAFT & BEARINGS (IN BLOCK) (Continued)

(2) Aline camshaft and crankshaft centerline.
Remove camshaft sprocket attaching bolt and remove
timing chain and camshaft sprockets.
(3) Use puller 6444 and jaws 6820 to remove
crankshaft sprocket (Fig. 79).
INSPECTIONÐMEASURING TIMING CHAIN
STRETCH
(1) Place a scale next to the timing chain so that
any movement of the chain may be measured.
(2) Place a torque wrench and socket over cam-
shaft sprocket attaching bolt. Apply torque in the
direction of crankshaft rotation to take up slack; 41
N´m (30 ft. lbs.) torque with cylinder head installed
or 20 N´m (15 ft. lbs.) torque with cylinder head
removed. With a torque applied to the camshaft
sprocket bolt, crankshaft should not be permitted to
move. It may be necessary to block the crankshaft to
prevent rotation.
(3) Hold a scale with dimensional reading even
with the edge of a chain link. With cylinder heads
installed, apply 14 N´m (30 ft. lbs.) torque in the
reverse direction. With the cylinder heads removed,
apply 20 N´m (15 ft. lbs.) torque in the reverse direc-
tion. Note the amount of chain movement (Fig. 80).
(4) Install a new timing chain, if its movement
exceeds 3.175 mm (1/8 inch).
INSTALLATION
(1) Line up key in crankshaft with keyway in
sprocket, press on crankshaft timing sprocket, use
tools C-3688, C-3718 and MB-990799, seat sprocket
against crankshaft shoulder (Fig. 81).
Fig. 79 Crankshaft Sprocket Removal.
1 - SPECIAL TOOL 6444
2 - SPECIAL TOOL 6820
Fig. 80 Measuring Timing Chain Stretch
1 - TORQUE WRENCH
2 - 3.175 MM (0.125 IN.)
Fig. 81 Crankshaft Sprocket Installation
1 - SPECIAL TOOL C-3688
2 - SPECIAL TOOL C-3718
3 - SPECIAL TOOL MD990799
BR/BEENGINE 8.0L 9 - 227
TIMING BELT/CHAIN AND SPROCKETS (Continued)

(7) Remove the tappet installation tool from the
tappet.
(8) Re-install a dowel rod and secure the rod with
a rubber band.
(9) Rotate the trough one half turn and repeat the
procedure for the remaining tappets.
(10) Install the camshaft (Refer to 9 - ENGINE/
ENGINE BLOCK/CAMSHAFT & BEARINGS (IN
BLOCK) - INSTALLATION).
PISTON & CONNECTING ROD
DESCRIPTION
The piston (Fig. 123) is constructed of aluminum
and is gravity cast, free floating design. The piston
incorporates a centrally located high swirl combus-
tion bowl, and utilizes a ªkeystoneº style top com-
pression ring (Fig. 124), and a ªTapered Faceº
intermediate ring (Fig. 124), for superior cylinder
wall scraping. Piston cooling nozzles cool the pistonand pin with engine oil supplied by the crankshaft
main journals.
The connecting rods (Fig. 125) are a split angle
design constructed of micro alloy. The rods have a
pressed in place wrist pin bushing which is lubri-
cated by the piston cooling nozzle oil spray.
STANDARD PROCEDUREÐPISTON GRADING
²When rebuilding an engine with the original cylin-
der block, crankshaft and pistons, make sure the pis-
tons are installed in their original cylinder.
²If replacing the piston(s), make sure the replace-
ment piston(s) are the same grade as the one being
replaced.
Fig. 120 Retrieve Tappet Installation Tool through
Cam Bore
Fig. 121 Insert Tool and Pull Tappet Into Place
Fig. 122 Rotate Trough One Half Turn (180É)
Fig. 123 Piston
9 - 282 ENGINE 5.9L DIESELBR/BE
SOLID LIFTERS/TAPPETS (Continued)

(4) Connect the 0-414 kPa (0-60 psi) fuel pressure
test gauge (from Gauge Set 5069) to the test port on
the appropriate Adaptor Tool.The DRBtIII Scan
Tool along with the PEP module, the 500 psi
pressure transducer, and the transducer-to-test
port adapter may also be used in place of the
fuel pressure gauge.
The fittings on both tools must be in good
condition and free from any small leaks before
performing the proceeding test.
(5) Start engine and bring to normal operating
temperature.
(6) Observe test gauge. Normal operating pressure
should be 339 kPa +/±34 kPa (49.2 psi +/±5 psi).
(7) Shut engine off.
(8) Pressure should not fall below30 psi for five
minutes.
(9) If pressure falls below 30 psi, it must be deter-
mined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking.
(10) Again, start engine and bring to normal oper-
ating temperature.
(11) Shut engine off.
(12)Testing for fuel injector or fuel rail leak-
age:Clamp off the rubber hose portion of Adaptor
Tool between the fuel rail and the test port ªTº on
Adapter Tool. If pressure now holds at or above 30
psi, a fuel injector or the fuel rail is leaking.
(13)Testing for fuel pump check valve, filter/
regulator check valve or fuel tube/line leakage:
Clamp off the rubber hose portion of Adaptor Tool
between the vehicle fuel line and test port ªTº on
Adapter Tool. If pressure now holds at or above 30
psi, a leak may be found at a fuel tube/line. If no
leaks are found at fuel tubes or lines, one of the
check valves in either the electric fuel pump or filter/
regulator may be leaking.
Note: A quick loss of pressure usually indicates a
defective check valve in the filter/regulator. A slow
loss of pressure usually indicates a defective check
valve in the electric fuel pump.
The electric fuel pump is not serviced separately.
Replace the fuel pump module assembly. The filter/
regulator may be replaced separately on certain
applications. Refer to Fuel Filter/Fuel Pressure Reg-
ulator Removal/Installation for additional informa-
tion.STANDARD PROCEDURE - FUEL SYSTEM
PRESSURE RELEASE
Use following procedure if the fuel injector
rail is, or is not equipped with a fuel pressure
test port.
(1) Remove fuel fill cap.
(2) Remove fuel pump relay from Power Distribu-
tion Center (PDC). For location of relay, refer to label
on underside of PDC cover.
(3) Start and run engine until it stalls.
(4) Attempt restarting engine until it will no
longer run.
(5) Turn ignition key to OFF position.
CAUTION: Steps 1, 2, 3 and 4 must be performed to
relieve high pressure fuel from within fuel rail. Do
not attempt to use following steps to relieve this
pressure as excessive fuel will be forced into a cyl-
inder chamber.
(6) Unplug connector from any fuel injector.
(7) Attach one end of a jumper wire with alligator
clips (18 gauge or smaller) to either injector terminal.
(8) Connect other end of jumper wire to positive
side of battery.
(9) Connect one end of a second jumper wire to
remaining injector terminal.
CAUTION: Powering an injector for more than a few
seconds will permanently damage the injector.
(10) Momentarily touch other end of jumper wire
to negative terminal of battery for no more than a
few seconds.
(11) Place a rag or towel below fuel line quick-con-
nect fitting at fuel rail.
(12) Disconnect quick-connect fitting at fuel rail.
Refer to Quick-Connect Fittings.
(13) Return fuel pump relay to PDC.
(14) One or more Diagnostic Trouble Codes (DTC's)
may have been stored in PCM memory due to fuel
pump relay removal. The DRBtscan tool must be
used to erase a DTC.
BR/BEFUEL DELIVERY - GASOLINE 14 - 3
FUEL DELIVERY - GASOLINE (Continued)

(1) Be sure fuel tank contains fuel before starting
test. If tank is empty or near empty, amperage read-
ings will be incorrect.
(2) Obtain LCS adapter.
(3) Plug cable from LCS adapter into DRB scan
tool at SET 1 receptacle.
(4) Plug DRB into vehicle 16±way connector (data
link connector).
(5) Connect (-) and (+) test cable leads into LCS
adapter receptacles. Use10 amp (10A +)receptacle
and common (-) receptacles.
(6) Gain access to MAIN MENU on DRB screen.
(7) Press DVOM button on DRB.
(8) Using left/right arrow keys, highlight CHAN-
NEL 1 function on DRB screen.
(9) Press ENTER three times.
(10) Using up/down arrow keys, highlight RANGE
on DRB screen (screen will default to 2 amp scale).
(11) Press ENTER to change 2 amp scale to 10
amp scale.This step must be done to prevent
damage to DRB scan tool or LCS adapter
(blown fuse).
(12) Remove cover from Power Distribution Center
(PDC).
(13) Remove fuel pump relay from PDC. Refer to
label on PDC cover for relay location.
WARNING: BEFORE PROCEEDING TO NEXT STEP,
NOTE THE FUEL PUMP WILL BE ACTIVATED AND
SYSTEM PRESSURE WILL BE PRESENT. THIS WILL
OCCUR AFTER CONNECTING TEST LEADS FROM
LCS ADAPTER INTO FUEL PUMP RELAY CAVITIES.
THE FUEL PUMP WILL OPERATE EVEN WITH IGNI-
TION KEY IN OFF POSITION. BEFORE ATTACHING
TEST LEADS, BE SURE ALL FUEL LINES AND
FUEL SYSTEM COMPONENTS ARE CONNECTED.
CAUTION: To prevent possible damage to the vehi-
cle electrical system and LCS adapter, the test
leads must be connected into relay cavities exactly
as shown in following steps.
Depending upon vehicle model, year or engine con-
figuration, three different types of relays may be
used: Type-1, type-2 and type±3.
(14) If equipped withtype±1 relay(Fig. 13),
attach test leads from LCS adapter into PDC relay
cavities number 30 and 87. For location of these cav-
ities, refer to numbers stamped to bottom of relay
(Fig. 13).
(15) If equipped withtype±2 relay(Fig. 14),
attach test leads from LCS adapter into PDC relay
cavities number 30 and 87. For location of these cav-
ities, refer to numbers stamped to bottom of relay
(Fig. 14).(16) If equipped withtype±3 relay(Fig. 15),
attach test leads from LCS adapter into PDC relay
cavities number 3 and 5. For location of these cavi-
ties, refer to numbers stamped to bottom of relay
(Fig. 15).
Fig. 13 FUEL PUMP RELAY - TYPE 1
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
Fig. 14 FUEL PUMP RELAY - TYPE 2
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
BR/BEFUEL DELIVERY - GASOLINE 14 - 11
FUEL PUMP (Continued)

(5) Install new plastic tie strap (Fig. 28) to secure
sensor pigtail harness to side of engine block. Thread
tie strap through casting hole on cylinder block.
FUEL PUMP RELAY
DESCRIPTION
The 5±pin, 12±volt, fuel pump relay is located in
the Power Distribution Center (PDC). Refer to the
label on the PDC cover for relay location.
OPERATION
The Powertrain Control Module (PCM) energizes
the electric fuel pump through the fuel pump relay.
The fuel pump relay is energized by first applying
battery voltage to it when the ignition key is turned
ON, and then applying a ground signal to the relay
from the PCM.
Whenever the ignition key is turned ON, the elec-
tric fuel pump will operate. But, the PCM will shut-
down the ground circuit to the fuel pump relay in
approximately 1±3 seconds unless the engine is oper-
ating or the starter motor is engaged.
REMOVAL
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 31). Refer to label on PDC
cover for relay location.
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 31). Refer to label on PDC
cover for relay location.
(1) Install relay to PDC.
(2) Install cover to PDC.
IDLE AIR CONTROL MOTOR
DESCRIPTION
The IAC stepper motor is mounted to the throttle
body, and regulates the amount of air bypassing the
control of the throttle plate. As engine loads and
ambient temperatures change, engine rpm changes.
A pintle on the IAC stepper motor protrudes into a
passage in the throttle body, controlling air flow
through the passage. The IAC is controlled by the
Powertrain Control Module (PCM) to maintain the
target engine idle speed.
OPERATION
At idle, engine speed can be increased by retract-
ing the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by
restricting the passage with the pintle and diminish-
ing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is
moved (rotated) in steps, or increments. Opening the
IAC opens an air passage around the throttle blade
which increases RPM.
The PCM uses the IAC motor to control idle speed
(along with timing) and to reach a desired MAP dur-
ing decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of
the wires are for 12 volts and ground to supply electri-
cal current to the motor windings to operate the step-
per motor in one direction. The other 2 wires are also
for 12 volts and ground to supply electrical current to
operate the stepper motor in the opposite direction.
To make the IAC go in the opposite direction, the
PCM just reverses polarity on both windings. If only
1 wire is open, the IAC can only be moved 1 step
(increment) in either direction. To keep the IAC
motor in position when no movement is needed, the
PCM will energize both windings at the same time.
This locks the IAC motor in place.
In the IAC motor system, the PCM will count
every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the
memory is cleared, the PCM no longer knows the
position of the pintle. So at the first key ON, the
PCM drives the IAC motor closed, regardless of
where it was before. This zeros the counter. From
this point the PCM will back out the IAC motor and
keep track of its position again.
Fig. 31 Power Distribution Center (PDC)
1 - POWER DISTRIBUTION CENTER (PDC)
BR/BEFUEL INJECTION - GASOLINE 14 - 41
CRANKSHAFT POSITION SENSOR (Continued)

(1) Install IAC motor to throttle body.
(2) Install and tighten two mounting bolts (screws)
to 7 N´m (60 in. lbs.) torque.
(3) Install electrical connector.
(4) Install air cleaner assembly.
INSTALLATION - 8.0L
The IAC motor is located on the back of the throt-
tle body (Fig. 33).
(1) Install IAC motor to throttle body.
(2) Install and tighten two mounting bolts (screws)
to 7 N´m (60 in. lbs.) torque.
(3) Install electrical connector.
(4) Install air cleaner housing to throttle body.
(5) Install 4 air cleaner housing mounting nuts.
Tighten nuts to 11 N´m (96 in. lbs.) torque.
(6) Install air cleaner housing cover.
INTAKE AIR TEMPERATURE
SENSOR
DESCRIPTION - 3.9L/5.2L/5.9L/8.0L
The 2±wire Intake Manifold Air Temperature (IAT)
sensor is installed in the intake manifold with the
sensor element extending into the air stream.
The IAT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as intake mani-
fold temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION - 3.9L/5.2L/5.9L/8.0L
The IAT sensor provides an input voltage to the
Powertrain Control Module (PCM) indicating the
density of the air entering the intake manifold based
upon intake manifold temperature. At key-on, a
5±volt power circuit is supplied to the sensor from
the PCM. The sensor is grounded at the PCM
through a low-noise, sensor-return circuit.
The PCM uses this input to calculate the following:
²Injector pulse-width
²Adjustment of spark timing (to help prevent
spark knock with high intake manifold air-charge
temperatures)
The resistance values of the IAT sensor is the same
as for the Engine Coolant Temperature (ECT) sensor.
REMOVAL - 3.9L/5.2L/5.9L
The intake manifold air temperature sensor is
located in the front/side of the intake manifold (Fig.
34).
(1) Remove air cleaner assembly.
(2) Disconnect electrical connector at sensor (Fig.
34).
(3) Remove sensor from intake manifold.
REMOVAL - 8.0L
The intake manifold air temperature sensor is
located in the side of the intake manifold near the
front of throttle body (Fig. 35).
(1) Disconnect electrical connector at sensor.
(2) Remove sensor from intake manifold.
INSTALLATION - 3.9L/5.2L/5.9L
The intake manifold air temperature sensor is
located in the front/side of the intake manifold (Fig.
34).
Fig. 34 Air Temperature SensorÐ3.9L/5.2L/5.9L
1 - INTAKE MANIFOLD AIR TEMPERATURE SENSOR
2 - ELECTRICAL CONNECTOR
Fig. 35 Air Temperature SensorÐ8.0L Engine
1 - INTAKE MANIFOLD AIR TEMP. SENSOR
2 - INTAKE MANIFOLD
BR/BEFUEL INJECTION - GASOLINE 14 - 43
IDLE AIR CONTROL MOTOR (Continued)