Page 2386 of 5267

OPERATION
High-pressure fuel is supplied from the injection pump, through a high-pressure fuel line, into a fuel rail, through
high-pressure lines, through steel connectors and into the solenoid actuated fuel injector. The ECM actuates the
solenoid causing the needle valve to rise and fuel flows through the spray holes in the nozzle tip into the combus-
tion chamber.
Each fuel injector is connected to the fuel rail by a high-pressure fuel line and a steel connector. This steel con-
nector is positioned into the cylinder head and sealed with an O-ring. The connector is retained in the cylinder head
by a nut (fitting) that is threaded into the cylinder head.
The torquing force of this threaded nut (fitting) provides a sealing pressure between the fuel line connector and the
fuel injector.Retaining nut torque is very critical.If the nut (fitting) is under torqued, the mating surfaces will not
seal and a high-pressure fuel leak will result. If the fitting is over torqued, the connector and injector will deform and
also cause a high-pressure fuel leak. This leak will be inside the cylinderhead and will not be visible. The result will
be a possible fuel injector miss-fire and low power, or a no-start condition.
The fuel injectors use hole type nozzles. High-pressure flows into the side of the injector, the ECM activates the
solenoid causing the injector needle to lift and fuel to be injected. The clearances in the nozzle bore are extremely
small and any dirt or contaminants will cause the injector to stick. Because of this, it is very important to do a
thorough cleaning of any lines before opening up any fuel system component. Always cover or cap any open fuel
connections before a fuel system repair is performed.
Each fuel injector connector tube contains an edge filter that is designedto break up small contaminants before
entering the fuel injector.The edge filters are not a substitute for proper cleaning and covering of allfuel
system components during repair.
The bottom of each fuel injector is sealed to the cylinder head with a1.5mmthick copper shim (gasket). The correct
thickness shim must always be re-installed after removing an injector.
Fuel pressure in the injector circuit decreases after injection. The injector needle valve is immediately closed and
fuel flow into the combustion chamber is stopped. Exhaust gases are prevented from entering the injector nozzle by
the needle valve.
REMOVAL
CAUTION: Refer to Cleaning Fuel System Parts.
Six individual, solenoid actuated high-pressure fuel
injectors (7) are used. The injectors are vertically
mounted into a bored hole in the top of the cylinder
head. This bored hole is located between the intake/
exhaust valves. High-pressure connectors, mounted
into the side of the cylinder head, connect each fuel
injector to each high-pressure fuel line.
1. Disconnect both negative battery cables from both batteries. Cover andisolate ends of cables.
2. Remove vanity cover.
3. Remove breather assembly and tubes.
Page 2391 of 5267

3. The bottom of fuel injector is sealed to cylinder
head bore with a copper sealing washer (shim) (1)
of a certain thickness. A new shim (1) with correct
thickness must always be re-installed after remov-
ing injector. Measure thickness of injector shim (1).
Shim Thickness: 1.5 mm (.060”)
4. Install new shim (1) (washer) to bottom of injector.
Apply light coating of clean engine oil to washer.
This will keep washer in place during installation.
5. Install new o-ring to fuel injector. Apply small
amount of clean engine oil to O-ring and injector
bore.
6. Install injector into cylinder head with male (high-
pressure) connector port facing the intake manifold.
Push down on fuel injector mounting flange to
engage O-ring and seat injector.
7. Tightening Sequence:
a. Install fuel injector holdown clamp (mounting
flange) bolts. Be sure the clamp is perpendicular to the injector body.Do a preliminary tightening of these
bolts to 5 Nꞏm (44 in. lbs.) torque. This preliminary tightening insures the fuel injector is seated and
centered.
b. After tightening, relieve bolt torque, but leave both bolts threaded inplace.
c. Install high-pressure connector and retaining nut. Do a preliminary tightening to 15 Nꞏm (11 ft. lbs.) torque.
d. Alternately tighten injector holdown bolts to 10 Nꞏm (89 in. lbs.) torque.
e. Do a final tightening of the high-pressure connector and retaining nut.Tighten to 50 Nꞏm (37 ft. lbs.) torque.
8. Install integrated gasket
9. Connect injector solenoid wires and nuts to top of injectors. Tighten connector nuts to 1.25 Nꞏm (11 in. lbs.)
torque.Be very careful not to overtighten these nuts as damage to fuel injector willoccur.
10. Install exhaust rocker arm assembly. Refer to the Diesel Engine section.
11. Set exhaust valve lash. Refer to the Diesel Engine section.
12. Install fuel connector tube nut at cylinder head and tighten to 50 Nꞏm (37ft.lbs.).Be sure to use a secondary
back-up wrench on the connector nut (fitting) while torquing fuel line fitting.Refer to Fuel Line Installation
for additional information.
13. Install valve cover (Refer to 9 - ENGINE/CYLINDER HEAD/CYLINDER HEAD COVER(S) - INSTALLATION).
14. Install breather assembly.
15. Connect negative battery cables to both batteries.
Page 2392 of 5267

FUEL INJECTOR RAIL
DESCRIPTION
The fuel injector rail is bolted to the top of the intake manifold.
OPERATION
The fuel rail is used as a distribution device to supply high-pressure fuelto the high-pressure fuel lines.
REMOVAL
CAUTION: Cleanliness cannot be overemphasized when handling or replacingdieselfuelsystemcompo-
nents. This especially includes the fuel injectors, high-pressure fuel lines and fuel injection pump. Very tight
tolerances are used with these parts. Dirt contamination could cause rapid part wear and possible plugging
of fuel injector nozzle tip holes. This in turn could lead to possible engine misfire. Always wash/clean any
fuel system component thoroughly before disassembly and then air dry. Capor cover any open part after
disassembly. Before assembly, examine each part for dirt, grease or othercontaminants and clean if nec-
essary. When installing new parts, lubricate them with clean engine oil orclean diesel fuel only.
1. Disconnect both negative battery cables at both
batteries. Isolate ends of both cables.
2. Disconnect electrical connector at fuel pressure
sensor.
3. Remove banjo bolt at fuel limiting valve.
4. Disconnect necessary wiring harness retention
clips from intake manifold.
5. Lift 2 rubber covers to gain access to positive (+),
intake heater cable nuts. Remove 2 nuts and
remove 2 cables from studs.
6. Carefully remove 4 high-pressure fuel lines from
top of fuel rail. Note position of each line while
removing.Do not bend lines while removing.
CAUTION: WHEN LOOSENING OR TIGHTENING
HIGH-PRESSURE LINES ATTACHED TO A SEPA-
RATE FITTING, USE A BACK-UP WRENCH ON FIT-
TING. DO NOT ALLOW FITTING TO ROTATE.
DAMAGE TO BOTH FUEL LINE AND FITTING WILL
RESULT.
7. Carefully remove 2 high-pressure fuel lines at each end of fuel rail. Note position of each line while removing.Do
not bend lines while removing.(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY/FUEL LINES - REMOVAL).
8. Remove fuel line connectinginjection pump to fuel rail.
9. Remove three injection rail mounting bolts.
10. Remove rail from top of intake manifold.
Page 2393 of 5267
INSTALLATION
1. Clean any dirt/debris from top of intake manifold
and bottom of fuel rail.
2. Position fuel rail to top of manifold and install 3
mounting bolts (1) finger tight.
3. Install all high-pressure lines to rail (Refer to 14 -
FUEL SYSTEM/FUEL DELIVERY/FUEL LINES -
REMOVAL) (Refer to 14 - FUEL SYSTEM/FUEL
DELIVERY/FUEL LINES - INSTALLATION). Torque
to 30 Nꞏm (22 ft. lbs.).
4. Tighten 3 mounting bolts at fuel rail. Torque bolts to
24 Nꞏm (18 ft. lbs.).
5. Reposition wiring harness to intake elbow and
install nut.
6. Install and tighten fuel limiting valve banjo bolt.
Copper washer against fuel limiting valve, rubber
seal against banjo bolt. Torque to 24 Nꞏm (18 ft.
lbs.).
7. Connect electrical connector to fuel pressure sen-
sor.
8. Position 2 positive (+) cables to intake heater
studs. Install 2 nuts.
9. Connect battery cables to both batteries.
10. Start engine and check for leaks.
Page 2397 of 5267

HEATER - INTAKE AIR
DESCRIPTION
The intake manifold air heater element assembly is located in the top of theintake manifold.
OPERATION
The air heater element is used to heat incoming air to the intake manifold. This is done to help engine starting and
improve driveability with cool or cold outside temperatures.
Electrical supply for the air heater element is controlled by the Engine Control Module (ECM) through the air heater
relay. Refer to Intake Manifold Air Heater Relay for more information.
One heavy-duty cable connects the air heater element to the air heater relay. This cable will supply 12 volts to an
individual heating element within the heater block assembly.
CAUTION: The heater elements are no longer grounded using an external ground strap. Grounding is now
accomplished using two electrically conductive gaskets. Failure to use these gaskets will result in faulty
heater element operation.
Refer to the Powertrain Diagnostic Procedures manual for electrical operation and complete description of the intake
heaters, including pre-heat and post-heat cycles.
REMOVAL
If servicing the heater element, the entire block/ele-
ment assembly must be replaced.
1. Disconnect both negative battery cables at both
batteries. Cover and isolate ends of both cables.
2. Remove both the intake manifold air intake tube
(above injection pump), and its rubber connector
hose (2).
Page 2399 of 5267
INSTALLATION
If servicing the heater element, the entire block/ele-
ment assembly must be replaced.
CAUTION: The heater elements are no longer
grounded using an external ground strap. Ground-
ing is now accomplished using two electrically
conductive gaskets. Failure to use these gaskets
will result in faulty heater element operation.
1. Using 2 new gaskets, position element assembly
and air housing to intake manifold (2).
2. Install wire harness clips to intake connection stud.
3. Install 4 housing bolts (1) and tighten to 24 Nꞏm
(18 ft. lbs.) torque.
4. Connect 2 positive (+) heater cables (6) at cable
mounting studs.Do not allow either of the cable
eyelets to contact any other metal source other
than the cable nuts/studs.
5. Install engine oil dipstick tube and mounting bolt
(5).
6. Connect rubber connector hose and intake tube to
air intake housing. Tighten clamp bolts to 11 Nꞏm
(100 in. lbs.) torque.
7. Connect both negative battery cables at both
batteries.
Page 2400 of 5267

RELAY - INTAKE AIR HEATER
DESCRIPTION
The intake manifold air heater relay (4) is located in
the engine compartment.
OPERATION
The Engine Control Module (ECM) operates the heating element through the intake manifold air heater relay. Refer
to Powertrain Diagnostic Procedures for an electrical operation and complete description of the intake heater, includ-
ing pre-heat and post-heat cycles.
REMOVAL
The two intake manifold air heater relays (4) are
located in the engine compartment. They are attached
to a common bracket. This bracket is attached to the
right battery tray.
The mounting bracket and both relays are replaced as
an assembly.
1. Disconnect both negative battery cables at both
batteries.
2. Disconnect four relay trigger wires at both relays.
Note position of wiring before removing.
3. Lift four rubber shields from all 4 cables.
4. Remove four nuts at cable connectors. Note posi-
tion of wiring before removing.
5. Remove relay mounting bracket bolts and remove
relay assembly.
Page 2401 of 5267
INSTALLATION
1. Install relay assembly (4) to battery tray. Tighten
mounting bolts to 4.5 Nꞏm (40 in. lbs.) torque.
2. Connect eight electrical connectors to relays.
3. Connect battery cables to both batteries.