Page 1385 of 2255

(7) Because fuel pump relay was removed, a Diag-
nostic Trouble Code (DTC) may have been set. After
testing is completed, and relay has been installed,
use DRB scan tool to remove DTC.
Fuel Supply Restriction Test:
Due to very small vacuum specifications, the DRB
scan tool along with the Periphal Expansion Port
(PEP) Module and 0±15 psi transducer must be used.
(8) Verify transfer pump pressure is OK before
performing restriction test.
(9) Locate and disconnect fuel supply line quick-
connect fitting at left-rear of engine (Fig. 63). After
disconnecting line, plastic clip will remain attached
to metal fuel line at engine. Carefully remove clip
from metal line. Snap same clip into fuel supply
hose.
(10) Install Special Rubber Adapter Hose Tool
6631 (3/8º) into ends of disconnected fuel supply line.
(11) Install transducer from PEP module to brass
ªTº fitting on tool 6631.
(12) Hook up DRB scan tool to transducer.
WARNING: DO NOT STAND IN LINE WITH THE
COOLING FAN FOR THE FOLLOWING STEPS.
(13) Start engine and record vacuum reading with
engine speed at high-idle (high-idle means engine
speed is at 100 percent throttle and no load). The
fuel restriction testMUSTbe done with engine speed
at high-idle.
(14) If vacuum reading islessthan 6 in/hg. (0±152
mm hg.), test is OK. If vacuum reading ishigher
than 6 in/hg. (152 mm hg.), restriction exists in fuel
supply line or in fuel tank module. Check fuel supply
line for damage, dents or kinking. If OK, remove
module and check module and lines for blockage.
Also check fuel pump inlet filter at bottom of module
for obstructions.
Testing For Air Leaks in Fuel Supply Side:
(15) A 3±foot section of 3/8º I.D. clear tubing is
required for this test.
(16) Using a tire core valve removal tool, carefully
remove core valve from inlet fitting test port.
(17) Attach and clamp the 3/8ºclear hose to fitting
nipple.
(18) Place other end of hose into a large clear con-
tainer. Allow hose to loop as high as possibleabove
test port.
(19) The fuel transfer pump can be put into a 25
second run (test) mode if key is quickly turned to
crank position and released back to run position
without starting engine.
To prevent engine from starting in this test, first
remove fuel system relay (fuel injection pump relay).
Relay is located in Power Distribution Center (PDC).
Refer to label under PDC cover for relay location.
Because fuel pump relay was removed, a DiagnosticTrouble Code (DTC) may have been set. After testing
is completed, and relay has been installed, use DRB
scan tool to remove DTC.
(20) Allow air to purge from empty hose before
examining for air bubbles. Air bubbles should not be
present.
(21) If bubbles are present, check for leaks in sup-
ply line to fuel tank.
(22) If supply line is not leaking, remove fuel tank
module and remove filter at bottom of module (filter
snaps to module). Check for leaks between supply
nipple at top of module, and filter opening at bottom
of module. Replace module if necessary.
(23) After performing test, install core back into
test fitting. Before installing protective cap, be sure
fitting is not leaking.
REMOVAL
The fuel transfer pump (fuel lift pump) is located
on left side of engine, below and rearward of fuel fil-
ter (Fig. 64).
(1) Disconnect both negative battery cables at both
batteries.
Fig. 64 Fuel Transfer Pump Location
1 - OIL PRESSURE SENSOR
2 - PUMP BRACKET NUTS (3)
3 - SUPPORT BRACKET BOLT
4 - BANJO BOLT (REAR)
5 - FUEL SUPPLY LINE
6 - ELECTRICAL CONNECTOR
7 - BANJO BOLT (FRONT)
8 - FUEL TRANSFER PUMP
14 - 86 FUEL DELIVERY - DIESELBR/BE
FUEL TRANSFER PUMP (Continued)
Page 1386 of 2255

(2) Thoroughly clean area around transfer pump
and fuel lines of any contamination.
(3) Remove starter motor. Refer to Starter Remov-
al/Installation in 8, Starting System for procedures.
(4) Place a drain pan below the pump.
(5) Disconnect fuel line quick-connect fitting at
fuel supply line (Fig. 64) at rear of pump.
(6) Remove support bracket bolt at top of pump
(Fig. 64).
(7) Remove front and rear banjo bolts at pump
(Fig. 64).
(8) Disconnect electrical connector at side of pump
(Fig. 64).
(9) Remove three pump bracket nuts (Fig. 64) and
remove pump from vehicle.
INSTALLATION
The fuel transfer pump (fuel lift pump) is located
on left side of engine, below and rearward of fuel fil-
ter (Fig. 64).
(1) Install new gaskets to fuel supply line/support
bracket and banjo bolt at rear of pump. Install line
and banjo bolt to pump.Do nottighten banjo bolt at
this time.
(2) Install new gaskets to fuel line and banjo bolt
at front of pump.
(3) Position 3 pump studs into pump mounting
bracket and install 3 nuts.Do nottighten nuts at
this time.
(4) Install support bracket bolt (Fig. 64).Do not
tighten bolt at this time.
(5) Tighten 3 pump nuts to 12 N´m (9 ft. lbs.)
torque.
(6) Tighten both banjo bolts to 24 N´m (18 ft. lbs.)
torque.
(7) Tighten support bracket bolt 12 N´m (9 ft. lbs.)
torque.
(8) Connect electrical connector to pump (Fig. 64).
(9) Connect fuel line quick-connect fitting to fuel
supply line at rear of pump.
(10) Install starter motor. Refer to Starter Remov-
al/Installation in 8, Starting for procedures.
(11) Connect both negative battery cables at both
batteries.
(12) Bleed air at fuel supply line at side of fuel
injection pump. Refer to the Air Bleed Procedure.
(13) Start engine and check for leaks.
OVERFLOW VALVE
DESCRIPTION
The overflow valve is located on the side of the
injection pump (Fig. 65). It is also used to connect
the fuel return line (banjo fitting) to the fuel injection
pump.
OPERATION
Fuel volume from the fuel transfer (lift) pump will
always provide more fuel than the fuel injection
pump requires. The overflow valve (a check valve) is
used to route excess fuel through the fuel return line
and back to the fuel tank. Approximately 70% of sup-
plied fuel is returned to the fuel tank. The valve
opens at approximately 97 kPa (14 psi). If the check
valve within the assembly is sticking open, fuel
drainage of the injection pump could cause hard
starting.
If a Diagnostic Trouble Code (DTC) has been stored
for ªdecreased engine performance due to high injec-
tion pump fuel temperatureº, the overflow valve may
be stuck in closed position.
DIAGNOSIS AND TESTING - OVERFLOW VALVE
Fuel volume from the fuel transfer (lift) pump will
always provide more fuel than the fuel injection
pump requires. The overflow valve (a check valve) is
used to route excess fuel through the fuel return line
and back to the fuel tank. Approximately 70% of sup-
plied fuel is returned to the fuel tank. The valve is
located on the side of the injection pump (Fig. 66). It
is also used to connect the fuel return line (banjo fit-
ting) to the fuel injection pump. The valve opens at
approximately 97 kPa (14 psi). If the check valve
Fig. 65 Overflow Valve Location
1 - FUEL SUPPLY LINE
2 - FUEL RETURN LINE
3 - BANJO BOLT (TEST PORT FITTING)
4 - OVERFLOW VALVE
5 - BANJO FITTING
BR/BEFUEL DELIVERY - DIESEL 14 - 87
FUEL TRANSFER PUMP (Continued)
Page 1387 of 2255

within the assembly is sticking, low engine power or
hard starting may result.
If a Diagnostic Trouble Code (DTC) has been stored
for ªdecreased engine performance due to high injec-
tion pump fuel temperatureº, the overflow valve may
be stuck in closed position.
A rubber tipped blow gun with regulated air line
pressure is needed for this test.
(1) Clean area around overflow valve and fuel
return line at injection pump before removal.
(2) Remove valve from pump and banjo fitting.
(3) Discard old sealing gaskets.
(4) Set regulated air pressure to approximately 97
kPa (14±16 psi).
(5) Using blow gun, apply pressure to overflow
valve inlet end (end that goes into injection pump).
(6) Internal check valve should release, and air
should pass through valve at 97 kPa (14±16 psi). If
not, replace valve.
(7) Reduce regulated air pressure to 10 psi and
observe valve. Valve should stay shut. If not, replace
valve.
(8) Install new sealing gaskets to valve.
(9) Install valve through banjo fitting and into
pump.
(10) Tighten to 30 N´m (24 ft. lbs.) torque.REMOVAL
The overflow valve (pressure relief valve) is located
at the outside of fuel injection pump (Fig. 67). It con-
nects the fuel return line (banjo fitting) to the pump.
The valve has no internal serviceable parts and must
be replaced as an assembly. Two sealing gaskets are
used. One gasket is located between pump and banjo
fitting. The other is located between the banjo fitting
and end of valve.
(1) Clean area around overflow valve and fuel
return line at injection pump before removal.
(2) Remove valve from pump and banjo fitting.
(3) Discard old sealing gaskets.
INSTALLATION
The overflow valve (pressure relief valve) is located
at the outside of fuel injection pump (Fig. 67). It con-
nects the fuel return line (banjo fitting) to the pump.
The valve has no internal serviceable parts and must
be replaced as an assembly. Two sealing gaskets are
used. One gasket is located between pump and banjo
fitting. The other is located between the banjo fitting
and end of valve.
(1) Install new sealing gaskets to valve.
(2) Install valve through banjo fitting and into
pump.
(3) Tighten to 30 N´m (24 ft. lbs.) torque.
Fig. 66 Overflow Valve Location
1 - FUEL SUPPLY LINE
2 - FUEL RETURN LINE
3 - BANJO BOLT (TEST PORT FITTING)
4 - OVERFLOW VALVE
5 - BANJO FITTING
Fig. 67 Overflow Valve Location
1 - FUEL SUPPLY LINE
2 - FUEL RETURN LINE
3 - BANJO BOLT (TEST PORT FITTING)
4 - OVERFLOW VALVE
5 - BANJO FITTING
14 - 88 FUEL DELIVERY - DIESELBR/BE
OVERFLOW VALVE (Continued)
Page 1388 of 2255

WATER IN FUEL SENSOR
DESCRIPTION
The WIF sensor is located on the side of the fuel
filter/water separator canister (Fig. 68).
OPERATION
The sensor sends an input to the Engine Control
Module (ECM) when it senses water in the fuel filter/
water separator. As the water level in the filter/sep-
arator increases, the resistance across the WIF
sensor decreases. This decrease in resistance is sent
as a signal to the ECM and compared to a high
water standard value. Once the value reaches 30 to
40 kilohms, the ECM will activate the water-in-fuel
warning lamp through CCD bus circuits. This all
takes place when the ignition key is initially put in
the ON position. The ECM continues to monitor the
input at the end of the intake manifold air heater
post-heat cycle.
REMOVAL
The Water-In-Fuel (WIF) sensor is located at the
side of fuel filter/water separator canister. Refer to
Fuel Filter/Water Separator Removal/Installation for
WIF sensor removal/installation procedures.
FUEL DRAIN MANIFOLD
DESCRIPTION
The fuel drain manifold is actually a rifled passage
within the cylinder head (Fig. 69).
OPERATION
When the engine is running, and during injection,
a small amount of fuel flows past the injector nozzle
and is not injected into the combustion chamber. This
fuel is used to lubricate the fuel injectors. Excess fuel
drains into the fuel drain manifold (or passage). Fuel
is drained from this passage into a line at the rear of
the cylinder head (Fig. 69). After exiting the cylinder
head, fuel is routed (returned) back to the fuel tank.
A ªTº is installed into the fuel return line (Fig. 69).
This ªTº is used to allow excess fuel from the injec-
tion pump to be returned into the fuel tank. A one-
way check valve within the overflow valve prevents
fuel (from the fuel drain manifold) from entering the
fuel injection pump.
Asmallamount of fuel is returned from the fuel
injectors, while alargeamount (about 70% of sup-
plied fuel) is returned from the fuel injection pump.
Fig. 68 Water-in-Fuel Sensor Location
1 - WATER-IN-FUEL (WIF) SENSOR
2 - FUEL FILTER/WATER SEPARATOR
3 - WIF SENSOR CONNECTOR
Fig. 69 Fuel Drain Manifold Passage
1 - REAR OF CYLINDER HEAD
2 - BANJO FITTING/BOLT
3 - FUEL RETURN TO TANK
4 - FUEL RETURN LINES
5 - FUEL RETURN LINE FROM PUMP OVERFLOW VALVE
6 - FUEL DRAIN MANIFOLD PASSAGE
7 - ªTº
BR/BEFUEL DELIVERY - DIESEL 14 - 89
Page 1389 of 2255

REMOVAL
The fuel drain manifold (line) connects a fuel
return passage within the cylinder head to a ªTº fit-
ting on the fuel return line. It is located at the rear
of the cylinder head.
(1) Disconnect both negative battery cables at both
batteries.
(2) Remove starter motor. Refer to Group 8B for
procedures.
(3) Disconnect fitting at ªTº (Fig. 70).(4) Remove banjo bolt at rear of cylinder head.
Discard old sealing washers.
(5) Remove fuel line from vehicle.
(6) Clean connection at rear of cylinder head
before line installation.
INSTALLATION
The fuel drain manifold (line) connects a fuel
return passage within the cylinder head to a ªTº fit-
ting on the fuel return line. It is located at the rear
of the cylinder head.
Servicing fuel return components will not require
air bleeding.
(1) Using new sealing washers, assemble banjo
bolt to fuel line.
(2) Position line to engine and loosely tighten fas-
teners.
(3) Tighten banjo bolt to 24 N´m (18 ft. lbs.)
torque.
(4) Tighten fitting at ªTº to 12 N´m (106 in. lbs.)
torque.
(5) Install starter motor. Refer to 8, Starter for
procedures.
(6) Connect both negative battery cables at both
batteries.
Fig. 70 Fuel Return Line at Rear of Cylinder Head
1 - REAR OF CYLINDER HEAD
2 - BANJO FITTING/BOLT
3 - FUEL RETURN TO TANK
4 - FUEL RETURN LINES
5 - FUEL RETURN LINE FROM PUMP OVERFLOW VALVE
6 - FUEL DRAIN MANIFOLD PASSAGE
7 - ªTº
14 - 90 FUEL DELIVERY - DIESELBR/BE
FUEL DRAIN MANIFOLD (Continued)
Page 1390 of 2255

FUEL INJECTION - DIESEL
TABLE OF CONTENTS
page page
FUEL INJECTION - DIESEL
DESCRIPTION - DIESEL FUEL INJECTION
SYSTEM............................91
DIAGNOSIS AND TESTING - BOOST
PRESSURE..........................93
SPECIFICATIONS
TORQUE - DIESEL ENGINE.............94
ACCELERATOR PEDAL POSITION SENSOR
DESCRIPTION.........................95
OPERATION...........................95
REMOVAL.............................95
INSTALLATION.........................97
FUEL INJECTOR
DESCRIPTION.........................97
OPERATION...........................98
DIAGNOSIS AND TESTINGÐFUEL INJECTOR
TEST...............................99
REMOVAL............................101
INSTALLATION........................102
FUEL INJECTION PUMP RELAY
DESCRIPTION........................103
OPERATION..........................103
FUEL TEMPERATURE SENSOR
DESCRIPTION........................104
OPERATION..........................104
INTAKE AIR HEATER
DESCRIPTION........................104OPERATION..........................104
REMOVAL............................104
INSTALLATION........................105
INTAKE AIR HEATER RELAY
DESCRIPTION........................105
OPERATION..........................105
REMOVAL............................106
INSTALLATION........................106
INTAKE AIR TEMPERATURE SENSOR
DESCRIPTION - DIESEL.................106
OPERATION - DIESEL..................106
REMOVAL - DIESEL....................107
INSTALLATION - DIESEL................107
MAP SENSOR
DESCRIPTION - DIESEL.................108
OPERATION - DIESEL..................108
REMOVAL - DIESEL....................108
INSTALLATION........................108
PTO SWITCH
DESCRIPTION
OPERATION........................108
THROTTLE CONTROL CABLE
REMOVAL............................109
INSTALLATION........................110
FUEL INJECTION - DIESEL
DESCRIPTION - DIESEL FUEL INJECTION
SYSTEM
The Engine Control Module (ECM) and Fuel Injec-
tion Pump Control Module (FPCM) are used prima-
rily for fuel system control. The ECM is a separate
replaceable component, while the FPCM is internal
to the fuel injection pump and is a non-serviceable
part. The ECM and FPCM are interconnected (wired
together) for fuel injection control.The Powertrain Control Module (PCM) is used to
regulate or control the A/C, charging and speed con-
trol systems. It is also used to partially control cer-
tain electronic automatic transmission components.
The PCM also has control over certain instrument
panel components.
Refer to either Powertrain Control Module (PCM)
or Engine Control Module (ECM) for additional infor-
mation. Refer to (Fig. 1) for a partial list of fuel sys-
tem components.
BR/BEFUEL INJECTION - DIESEL 14 - 91
Page 1391 of 2255
Fig. 1 FUEL SYSTEM COMPONENTS - DIESEL
1 - ENGINE COOLANT TEMPERATURE (ECT) SENSOR 14 - FUEL SUPPLY LINE (LOW-PRESSURE, TO ENGINE)
2 - THROTTLE LEVER BELLCRANK AND APPS (ACCELERATOR
PEDAL POSITION SENSOR)15 - FUEL TRANSFER (LIFT) PUMP
3 - INTAKE MANIFOLD AIR HEATER/ELEMENTS 16 - OIL PRESSURE SENSOR
4 - HIGH-PRESSURE FUEL LINES 17 - FUEL FILTER/WATER SEPARATOR
5 - FUEL HEATER 18 - DRAIN TUBE
6 - FUEL PRESSURE TEST PORT 19 - WATER-IN-FUEL (WIF) SENSOR
7 - MAP (BOOST) SENSOR 20 - ENGINE CONTROL MODULE (ECM)
8 - FUEL INJECTORS 21 - FUEL PRESSURE TEST PORT
9 - FUEL INJECTOR CONNECTOR 22 - CAMSHAFT POSITION SENSOR (CMP)
10 - INTAKE AIR TEMPERATURE (IAT) SENSOR 23 - OVERFLOW VALVE
11 - FUEL DRAIN MANIFOLD 24 - FUEL INJECTION PUMP
12 - DRAIN VALVE 25 - FUEL HEATER TEMPERATURE SENSOR (THERMOSTAT)
13 - FUEL RETURN LINE (TO FUEL TANK)
14 - 92 FUEL INJECTION - DIESELBR/BE
FUEL INJECTION - DIESEL (Continued)
Page 1392 of 2255

DIAGNOSIS AND TESTING - BOOST PRESSURE
Two pressure gauges attached at two different
points are required for this test.(1) Obtain two 6828 fuel pressure test gauges
(equivalent gauges are OK).Gauge Consistency
Test:Connect the gauges together to a common pres-
sure source and verify pressure consistency of both
gauges. Do this consistency test at approximately 206
kPa (30 psi). If pressures are different, they can still
be used for test. Note and record differences in pres-
sures before testing. Make adjustments as necessary.
(2) Remove 3/4º pipe plug fitting at rear of intake
manifold (Fig. 2). Temporarily replace this fitting
with fitting reducer to adapt to pressure gauge.
Note: This pipe plug is located to front of MAP
sensor. Do not remove plug to rear of MAP sen-
sor. This is a COOLANT passage plug.
(3) Loosen hose clamp and disconnect rubber sig-
nal line (Fig. 3) from 1/8º brass fitting at front of tur-
bocharger.
(4) Remove 1/8º brass fitting (Fig. 3) from turbo-
charger. Temporarily replace this fitting with a 1/8º
ªTº fitting to adapt to pressure gauge.
(5) Reattach signal line to temporary ªTº.
(6) Attach first pressure gauge to intake manifold
fitting.
(7) Attach second pressure gauge to ªTº fitting at
turbocharger.
Engine must be at rated RPM and full load for the
test.
If gauge pressure differential is greater than 3 psi
(6 in. Hg), check intercooler and associated piping for
restrictions, plugging or damage.
Maximum pressure at intake manifold (rated rpm
and load) is 36±37 in/hg 3 in/hg (17.7±18.2 psi
1.5 psi).
Wastegate should open at no higher than 38.7
in/hg (19 psi) at wide open throttle, full load. If
wastegate is out of adjustment, a DTC may have
been set. Refer to Wastegate Adjustment in Engines
for adjustment procedures.
Fig. 2 Boost Pressure Test at Intake Manifold
1 - REAR OF INTAKE MANIFOLD
2 - 3/49PIPE PLUG
Fig. 3 Boost Pressure Test at Turbocharger
1 - TURBOCHARGER
2 - 1/89FITTING
3 - SIGNAL LINE
4 - WASTEGATE ACTUATOR
5 - CONTROL ROD
6 - OIL SUPPLY LINE
BR/BEFUEL INJECTION - DIESEL 14 - 93
FUEL INJECTION - DIESEL (Continued)