check engine DODGE RAM 2003 Service Repair Manual

(5) Remove four throttle body mounting bolts (Fig.
47).
(6) Remove throttle body from intake manifold.
(7) Discard old throttle body-to-intake manifold
gasket.8.0L V-10
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the powertrain control module (PCM).
(1) Remove air plenum resonator.
(2) Disconnect throttle body electrical connectors
at the IAC motor and TPS.
(3) Remove all control cables from throttle body
(lever) arm. Refer to the Accelerator Pedal and Throt-
tle Cable section of this group for additional informa-
tion.
(4) Remove four throttle body mounting nuts (Fig.
48).
(5) Remove throttle body from intake manifold.
(6) Discard old throttle body-to-intake manifold
gasket.
INSTALLATION
3.7L V-6
(1) Check condition of throttle body-to-intake man-
ifold o-ring. Replace as necessary.
(2) Clean mating surfaces of throttle body and
intake manifold.
(3) Install throttle body-to-intake manifold o-ring.
(4) Install throttle body to intake manifold.
(5) Install 3 mounting bolts. Tighten bolts to 12
N´m (105 in. lbs.) torque.
Fig. 45 5.7L V-8 THROTTLE BODY O-RING
1 - INTAKE MANIFOLD
2 - THROTTLE BODY O-RING
Fig. 46 SENSOR ELECTRICAL CONNECTORS - 5.9L
V-8
1 - MAP SENSOR
2 - IDLE AIR CONTROL MOTOR
3 - THROTTLE POSITION SENSOR
Fig. 47 THROTTLE BODY MOUNTING BOLTS - 5.9L
V-8
1 - THROTTLE BODY MOUNTING BOLTS (4)
2 - THROTTLE BODY
DRFUEL INJECTION - GAS 14 - 47
THROTTLE BODY (Continued)

(6) Install control cables.
(7) Install electrical connectors.
(8) Install necessary vacuum lines.
(9) Install air plenum.
4.7L V-8
(1) Clean throttle body-to-intake manifold o-ring.
(2) Clean mating surfaces of throttle body and
intake manifold.
(3) Install throttle body to intake manifold by posi-
tioning throttle body to manifold alignment pins.
(4) Install three mounting bolts. Tighten bolts to
12 N´m (105 in. lbs.) torque.
(5) Install control cables.
(6) Install vacuum line to throttle body.
(7) Install electrical connectors.
(8) Install air plenum.
5.7L V-8
CAUTION: Do not use spray (carb) cleaners on any
part of the throttle body. Do not apply silicone lubri-
cants to any part of the throttle body.
(1) Clean and check condition of throttle body-to-
intake manifold o-ring.
(2) Clean mating surfaces of throttle body and
intake manifold.(3) Install throttle body to intake manifold by posi-
tioning throttle body to manifold alignment pins.
(4) Install 4 mounting bolts. Refer to Torque Spec-
ifications.
(5) Install electrical connector.
(6) Install air plenum.
(7)If the throttle body has been changed, the
following procedure must be performed:
(a) Disconnect negative battery cable from bat-
tery. Leave cable disconnected for approximately 90
seconds.
(b) Reconnect cable to battery.
(c) Turn ignition switch ON, but do not crank
engine.
(d) Leave ignition switch ON for a minimum of
10 seconds. This will allow PCM to learn throttle
body electrical parameters.
5.9L V-8
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the powertrain control module (PCM).
(1) Clean the mating surfaces of the throttle body
and the intake manifold.
(2) Install new throttle body-to-intake manifold
gasket.
(3) Install throttle body to intake manifold.
(4) Install four mounting bolts. Tighten bolts to 23
N´m (200 in. lbs.) torque.
(5) Install control cables.
(6) Install vacuum line to throttle body.
(7) Install electrical connectors.
(8) Install air plenum.
8.0L V-10
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the powertrain control module (PCM).
(1) Clean mating surfaces of throttle body and
intake manifold.
(2) Install new throttle body-to-intake manifold
gasket.
(3) Install throttle body to intake manifold.
(4) Install four mounting nuts (Fig. 48). Refer to
Torque Specifications.
(5) Install control cables.
(6) Install electrical connectors.
(7) Install air plenum and hoses.
Fig. 48 THROTTLE BODY MOUNTING NUTS - 8.0L
V-10
1 - INTAKE MANIFOLD UPPER HALF
2 - GASKET
3 - THROTTLE BODY
4 - MOUNTING NUTS (4)
14 - 48 FUEL INJECTION - GASDR
THROTTLE BODY (Continued)

(4) From inside vehicle, install metal clip holding
cable to dashpanel (Fig. 1).
(5) From inside vehicle, slide throttle cable core
wire into opening (slot) in top of pedal arm.
(6) Push plastic cable retainer (clip) into pedal arm
opening until it snaps in place.
(7) Install air resonator tube to throttle body.
(8) Before starting engine, operate accelerator
pedal to check for any binding.
4.7L V-8
(1) Slide accelerator cable plastic mount into
bracket. Continue sliding until tab (Fig. 52) is
aligned to hole in mounting bracket.
(2) Route accelerator cable over top of cable cam.
(3) Connect cable end to throttle body bellcrank
pin (snaps on rearward).
(4) Slide rubber grommet away from plastic cable
housing.
(5) Install rubber grommet into dash panel until
seated.
(6) Push cable housing into rubber grommet and
through opening in dash panel.
(7) From inside vehicle, install clip holding cable
to dashpanel (Fig. 1).
(8) From inside vehicle, slide throttle cable core
wire into opening in top of pedal arm.
(9) Push cable retainer (clip) into pedal arm open-
ing until it snaps in place.
(10) Snap cable into dashpanel routing clip.
(11) Install air resonator tube to throttle body.
(12) Before starting engine, operate accelerator
pedal to check for any binding.
5.7L V-8
(1) Attach cable to Accelerator Pedal Position Sen-
sor (APPS). Refer to APPS Removal / Installation.
(2) Push cable housing into rubber grommet and
through opening in dash panel.
(3) From inside vehicle, install clip holding cable
to dashpanel (Fig. 1).
(4) From inside vehicle, slide throttle cable core
wire into opening in top of pedal arm.
(5) Push cable retainer (clip) into pedal arm open-
ing until it snaps in place.
(6) Before starting engine, operate accelerator
pedal to check for any binding.
(7) If necessary, use DRB IIItScan Tool to erase
any APPS Diagnostic Trouble Codes (DTC's) from
PCM.
5.9L V-8
(1) Slide accelerator cable plastic mount into throt-
tle body mounting bracket. Continue sliding until
release tab (Fig. 54) is aligned to hole in mounting
bracket.(2) Hold throttle in wide open position. While held
in this position, slide throttle cable pin into throttle
body bellcrank.
(3) Push cable housing into rubber grommet and
through opening in dash panel.
(4) From inside vehicle, install metal clip holding
cable to dashpanel (Fig. 1).
(5) From inside vehicle, slide throttle cable core
wire into opening (slot) in top of pedal arm.
(6) Push plastic cable retainer (clip) into pedal arm
opening until it snaps in place.
(7) Install air resonator tube to throttle body.
(8) Before starting engine, operate accelerator
pedal to check for any binding.
8.0L V-10
(1) Connect cable end socket to throttle body lever
ball (snaps on) (Fig. 55).
(2) Connect cable to throttle body mounting
bracket (push down and lock)
(3) Install the remaining cable housing end into
and through the dash panel opening (snaps into posi-
tion). The two plastic pinch tabs (Fig. 1) should lock
the cable to dash panel.
(4) From inside the vehicle, hold up the accelera-
tor pedal. Install the throttle cable core wire and
plastic cable retainer into and through the upper end
of the pedal arm (the plastic retainer is snapped into
the pedal arm). When installing the plastic retainer
to the accelerator pedal arm, note the index tab on
the pedal arm (Fig. 1). Align the index slot on the
plastic cable retainer to this index tab.
(5) Install air resonator tube to throttle body.
(6) Before starting engine, operate accelerator
pedal to check for any binding.
THROTTLE POSITION SENSOR
DESCRIPTION
The 3-wire Throttle Position Sensor (TPS) is
mounted on the throttle body and is connected to the
throttle blade shaft.
The 5.7L V-8 engine does not use a separate TPS
on the throttle body.
OPERATION
The 5.7L V-8 engine does not use a separate Throt-
tle Position Sensor (TPS) on the throttle body.
The 3±wire TPS provides the Powertrain Control
Module (PCM) with an input signal (voltage) that
represents the throttle blade position of the throttle
body. The sensor is connected to the throttle blade
shaft. As the position of the throttle blade changes,
the output voltage of the TPS changes.
14 - 52 FUEL INJECTION - GASDR
THROTTLE CONTROL CABLE (Continued)

(3) Remove two TPS mounting bolts (Fig. 60).
(4) Remove TPS from throttle body.
INSTALLATION
3.7L V-6
The Throttle Position Sensor (TPS) is mounted to
the throttle body (Fig. 56).
The throttle shaft end of throttle body slides into a
socket in TPS (Fig. 61). The TPS must be installed so
that it can be rotated a few degrees. (If sensor will
not rotate, install sensor with throttle shaft on other
side of socket tangs). The TPS will be under slight
tension when rotated.
(1) Install TPS and retaining screws.
(2) Tighten screws to 7 N´m (60 in. lbs.) torque.
(3) Connect TPS electrical connector to TPS.
(4) Manually operate throttle (by hand) to check
for any TPS binding before starting engine.
(5) Install air cleaner tube to throttle body.
4.7L V-8
The throttle shaft end of throttle body slides into a
socket in TPS (Fig. 62). The TPS must be installed so
that it can be rotated a few degrees. If sensor will
not rotate, install sensor with throttle shaft on other
side of socket tangs. The TPS will be under slight
tension when rotated.
(1) Install TPS and two retaining bolts.
(2) Tighten bolts to 7 N´m (60 in. lbs.) torque.
(3) Manually operate throttle control lever by hand
to check for any binding of TPS.
(4) Connect TPS electrical connector to TPS.
Fig. 58 TPS LOCATION - 4.7L
1 - THROTTLE BODY
2 - TPS
3 - IAC MOTOR
4 - IAT SENSOR
5 - MOUNTING SCREWS
Fig. 59 TPS LOCATION - 5.9L V-8
1 - THROTTLE POSITION SENSOR
2 - MOUNTING SCREWS
Fig. 60 TPS MOUNTING BOLTS - 8.0L V-10
1 - MOUNTING BOLTS (2)
2 - IDLE AIR CONTROL MOTOR
3 - THROTTLE POSITION SENSOR
4 - THROTTLE BODY
14 - 54 FUEL INJECTION - GASDR
THROTTLE POSITION SENSOR (Continued)

FUEL FILTER / WATER
SEPARATOR
DESCRIPTION
The fuel filter/water separator assembly is located
on left side of engine above starter motor. The assem-
bly also includes the fuel heater and Water-In-Fuel
(WIF) sensor, and fuel transfer pump.
OPERATION
The fuel filter/water separator protects the fuel
injection pump by removing water and contaminants
from the fuel. The construction of the filter/separator
allows fuel to pass through it, but helps prevent
moisture (water) from doing so. Moisture collects at
the bottom of the canister.
Refer to the maintenance schedules for the recom-
mended fuel filter replacement intervals.
For draining of water from canister, refer to Fuel
Filter/Water Separator Removal/Installation section.A Water-In-Fuel (WIF) sensor is attached to side of
canister. Refer to Water-In-Fuel Sensor Description/
Operation.
The fuel heater is installed into the top of the fil-
ter/separator housing. Refer to Fuel Heater Descrip-
tion/Operation.
REMOVAL
Refer to maintenance schedules in this manual for
recommended fuel filter replacement intervals.
Draining water from fuel filter/water separa-
tor housing:
The housing drain valve (Fig. 3) or (Fig. 4) serves
two purposes. One is topartiallydrain filter hous-
ing of excess water. The other is tocompletelydrain
housing for fuel filter, drain valve, heater element, ,
water-in-fuel sensor replacement or transfer pump
replacement.
The filter housing should be partially drained
whenever water-in-fuel warning lamp remains illumi-
nated. (Note that lamp will be illuminated for
approximately two seconds when ignition key is ini-
tially placed in ON position for a bulb check).
(1) A drain hose (Fig. 3) or (Fig. 4) is located at
bottom of drain valve. Place drain pan under drain.
(2)With engine not running,rotate drain valve
handle rearward to OPEN (DRAIN) position. Hold
drain valve open until all water and contaminants
have been removed and clean fuel exits.
(3) If drain valve, fuel heater element or Water-In-
Fuel (WIF) sensor is being replaced, drain housing
completely. Dispose of mixture in drain pan according
to applicable regulations.
(4) After draining operation, push valve handle
forward to CLOSE position.
(5)Fuel Filter Replacement:The fuel filter is
located inside of the fuel filter housing.
(a) Clean all debris from around canister.
(b) Remove filter lid (Fig. 5) using a socket.
Attach socket to large hex on top of lid (Fig. 5).
Rotate counter-clockwise for removal. Remove
o-ring.
(c) Remove filter element by twisting element
sideways from filter lid.
(6)Water-In-Fuel (WIF) Sensor Replacement:
The WIF sensor is located on the side of the fuel fil-
ter housing (Fig. 3) or (Fig. 4).
(a) Disconnect electrical connector at sensor.
(b) Clean area around sensor.
(c) Remove sensor by rotating counter-clockwise.
(d) Check condition of sensor o-ring. Replace if
damaged.
(7)Fuel Heater Element Replacement:The
heater element is located in the fuel filter housing
(Fig. 3) or (Fig. 4).
(a) Remove fuel filter. See previous steps.
FUEL INJECTOR TUBE (CONNECTOR) REMOVER -
#9015
SPANNER WRENCH (FUEL TANK MODULE
REMOVAL/INSTALLATION) - #6856
ENGINE ROTATING (BARRING) TOOL - #7471B
(ALSO PART OF KIT #6860)
DRFUEL DELIVERY - DIESEL 14 - 61
FUEL DELIVERY - DIESEL (Continued)

(c) Position new element to canister lid. Place
this assembly into canister by rotating clockwise.
(d) Tighten cap to 34 N´m (25 ft. lbs.) torque. Do
not overtighten cap.
(3)Water-In-Fuel (WIF) Sensor:
(a) Install new o-ring seal to WIF sensor.
(b) Apply a light film of clean diesel oil to o-ring
seal.
(c) Install sensor into housing.
(d) Tighten sensor to 4.5 N´m (39 in. lbs.) torque.
(e) Connect electrical connector to WIF sensor.
(4)Fuel Heater Element:
(a) Install fuel heater into fuel filter housing.
(b) Install fuel heater thermostat into fuel filter
housing.
(c) Install fuel heater mounting screws and
tighten to 1-1.5 N´m torque.
(d) Connect electrical connector to fuel heater
thermostat.
(e) Install new filter cover O-ring onto fuel filter
housing cover and lubricate with 30W oil.
(f) Tighten fuel filter housing cover (lid) to 34
N´m (25 ft. lbs.).
(5)Drain Valve:
(a) Install 2 new o-rings to valve and filter hous-
ing.
(b) Lubricate with silicon grease.
(c) Install fuel drain valve.
(d) Install 4 mounting screws and tighten to
1±1.5 N´m (8±13 in. lbs.) torque.
(e) Connect drain hose to drain valve.
(6) Start engine and check for leaks.
FUEL HEATER
DESCRIPTION
The fuel heater assembly is located on the side of
the fuel filter housing (Fig. 3) or (Fig. 4).
The heater/element assembly is equipped with a
temperature sensor (thermostat) that senses fuel
temperature. This sensor is attached to the fuel heat-
er/element assembly.
OPERATION
The fuel heater is used to prevent diesel fuel from
waxing during cold weather operation.
When the temperature is below 45  8 degrees F,
the temperature sensor allows current to flow to the
heater element warming the fuel. When the temper-
ature is above 75  8 degrees F, the sensor stops cur-
rent flow to the heater element.
Battery voltage to operate the fuel heater element
is supplied from the ignition switch and through the
fuel heater relay. Also refer to Fuel Heater Relay.The fuel heater element and fuel heater relay
are not computer controlled.
The heater element operates on 12 volts, 300 watts
at 0 degrees F.
DIAGNOSIS AND TESTING - FUEL HEATER
The fuel heater is used to prevent diesel fuel from
waxing during cold weather operation.
NOTE: The fuel heater element, fuel heater relay
and fuel heater temperature sensor are not con-
trolled by the Engine Control Module (ECM), or the
Powertrain Control Module (PCM).
A malfunctioning fuel heater can cause a wax
build-up in the fuel filter/water separator. Wax
build-up in the filter/separator can cause engine
starting problems and prevent the engine from rev-
ving up. It can also cause blue or white fog-like
exhaust. If the heater is not operating in cold tem-
peratures, the engine may not operate due to fuel
waxing.
The fuel heater assembly is located on the side of
fuel filter housing.
The heater assembly is equipped with a built-in
fuel temperature sensor (thermostat) that senses fuel
temperature. When fuel temperature drops below 45
degrees   8 degrees F, the sensor allows current to
flow to built-in heater element to warm fuel. When
fuel temperature rises above 75 degrees   8 degrees
F, the sensor stops current flow to heater element
(circuit is open).
Voltage to operate fuel heater element is supplied
from ignition switch, through fuel heater relay (also
refer to Fuel Heater Relay), to fuel temperature sen-
sor and on to fuel heater element.
The heater element operates on 12 volts, 300 watts
at 0 degrees F. As temperature increases, power
requirements decrease.
A minimum of 7 volts is required to operate fuel
heater. The resistance value of heater element is less
than 1 ohm (cold) and up to 1000 ohms warm.
TESTING
(1) Disconnect electrical connector from thermostat
(Fig. 3) or (Fig. 4).
Ambient temperature must be below circuit close
temperature, If necessary, induce this ambient tem-
perature by placing ice packs on thermostat to pro-
duce an effective ambient temperature below circuit
close temperature. For first check of thermostat you
can hear click of thermostat when circuit closes.
Measure resistance across two pins. Operating
range is 0.3 Ð 0.45 Ohms.
(2) If resistance is out of range, remove thermostat
and check resistance across terminal connections of
DRFUEL DELIVERY - DIESEL 14 - 63
FUEL FILTER / WATER SEPARATOR (Continued)

heater. The heater can be check at room tempera-
ture. Operating range is 0.3 Ð 0.45 Ohms.
(3) Replace heater if resistance is not within oper-
ating range.
(4) If heater is within operating range, replace
heater thermostat.
REMOVAL
REMOVAL/INSTALLATION
The fuel heater/element/sensor assembly is located
inside of the fuel filter housing. Refer to Fuel Filter/
Water Separator Removal/Installation for procedures.
FUEL HEATER RELAY
DESCRIPTION
The fuel heater relay is located in Power Distribu-
tion Center (PDC) (Fig. 6). Refer to label on inside of
PDC cover for relay location.
OPERATION
Battery voltage to operate the fuel heater element
is supplied from the ignition switch through the fuel
heater relay.The fuel heater element and fuel
heater relay are not computer controlled.
REMOVAL
The fuel heater relay is located in the Power Dis-
tribution Center (PDC) (Fig. 7). Refer to label under
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 heater relay is located in the Power Dis-
tribution Center (PDC) (Fig. 7). Refer to label under
PDC cover for relay location.
(1) Install relay to PDC.
(2) Install cover to PDC.
FUEL INJECTION PUMP
DESCRIPTION
A Robert Bosch high-pressure fuel injection pump
is used. The pump is attached to the back of the tim-
ing gear cover at the left / rear side of the engine.
OPERATION
The fuel injection pump supplies high pressure to
the fuel rail independent of engine speed. This high
pressure is then accumulated in the fuel rail. High
pressure fuel is constantly supplied to the injectors
by the fuel rail. The Engine Control Module (ECM)
controls the fueling and timing of the engine by actu-
ating the injectors.
Fuel enters the system from the electric fuel trans-
fer (lift) pump, which is attached to the fuel filter
assembly. Fuel is forced through the fuel filter ele-
ment and then enters the Fuel Pump/Gear Pump,
which is attached to the rear of the fuel injection
Fig. 6 POWER DISTRIBUTION CENTER LOCATION
1 - CLIP
2 - BATTERY
3 - TRAY
4 - NEGATIVE CABLE
5 - POSITIVE CABLE
6 - CLIP
7 - FENDER INNER SHIELD
8 - POWER DISTRIBUTION CENTER
Fig. 7 POWER DISTRIBUTION CENTER LOCATION
1 - CLIP
2 - BATTERY
3 - TRAY
4 - NEGATIVE CABLE
5 - POSITIVE CABLE
6 - CLIP
7 - FENDER INNER SHIELD
8 - POWER DISTRIBUTION CENTER
14 - 64 FUEL DELIVERY - DIESELDR
FUEL HEATER (Continued)

(4) Apply clean engine oilto injection pump
o-ring only.
The machined tapers on both injection pump
shaft and injection pump gear must be abso-
lutely dry, clean and free of any dirt or oil film.
This will ensure proper gear-to-shaft tighten-
ing.
(5) Clean pump gear and pump shaft at machined
tapers with an evaporative type cleaner such as
brake cleaner.
(6) Position injection pump to mounting flange on
gear cover while aligning injection pump shaft
through back of injection pump gear.
(7) After pump is positioned flat to mounting
flange, install 3 pump mounting nuts and tighten
finger tight only.Do not attempt a final tightening
at this time.Do not attempt to tighten (pull)
pump to gear cover using mounting nuts. Dam-
age to pump or gear cover may occur. The
pump must be positioned flat to its mounting
flange before attempting to tighten 3 mounting
nuts.
(8) To prevent damage or cracking of components,
install and tighten nuts in the following sequence:
(a) Install injection pump shaft washer and nut
to pump shaft. Tighten nutfinger tight only.
(b) Do preliminary (light) tightening of injection
pump shaft nut.
(c) Tighten 3 injection pump mounting nuts to 8
N´m (70.8 in. lbs.).
(d) Do a final tightening of pump shaft nut to
105 N´m (77 ft. lbs.).
(9) Install drive gear access cover (plate) using a
1/2 inch drive ratchet. Plate is threaded to timing
gear cover.
(10) Install Engine Control Module (ECM) to left
side of engine.
(11) Install fuel line (injection pump-to-overflow
valve). Tighten bolts to 24 N´m (17 ft. lbs.) torque.
(12) Install fuel line (injection pump-to-fuel rail).
Tighten to 24 N´m (17 ft. lbs.) torque.
(13) Install fuel line (injection pump-to-fuel filter
housing). Tighten to 24 N´m (17 ft. lbs.) torque.
(14) Connect Fuel Control Actuator (FCA) electri-
cal connector to rear of injection pump.
(15) Install intake manifold air intake tube (above
injection pump). Tighten clamps.
(16) Install accessory drive belt.
(17) Install cooling fan shroud.
(18) Install cooling fan assembly.
(19) Connect both negative battery cables to both
batteries.
(20) Check system for fuel or engine oil leaks.FUEL LEVEL SENDING UNIT /
SENSOR
DESCRIPTION
The fuel gauge sending unit (fuel level sensor) is
attached to the side of the fuel tank module. The
sending unit consists of a float, an arm, and a vari-
able resistor track (card).
OPERATION
The fuel tank module on diesel powered models
has 3 different circuits (wires). Two of these circuits
are used at the fuel gauge sending unit for fuel
gauge operation. The other wire is used for a ground.
The diesel engine does not have a fuel tank module
mounted electric fuel pump. The electric fuel pump
(fuel transfer pump) is mounted to the engine.
For Fuel Gauge Operation:A constant input
voltage source of about 12 volts (battery voltage) is
supplied to the resistor track on the fuel gauge send-
ing unit. This is fed directly from the Powertrain
Control Module (PCM).NOTE: For diagnostic pur-
poses, this 12V power source can only be veri-
fied with the circuit opened (fuel tank module
electrical connector unplugged). With the con-
nectors plugged, output voltages will vary from
about .6 volts at FULL, to about 7.0 volts at
EMPTY.The resistor track is used to vary the volt-
age (resistance) depending on fuel tank float level. As
fuel level increases, the float and arm move up,
which decreases voltage. As fuel level decreases, the
float and arm move down, which increases voltage.
The varied voltage signal is returned back to the
ECM through the sensor return circuit.
Both of the electrical circuits between the fuel
gauge sending unit and the ECM are hard-wired (not
multi-plexed). After the voltage signal is sent from
the resistor track, and back to the ECM, the ECM
will interpret the resistance (voltage) data and send
a message across the multi-plex bus circuits to the
instrument panel cluster. Here it is translated into
the appropriate fuel gauge level reading. Refer to
Instrument Panel for additional information.
REMOVAL
REMOVAL/INSTALLATION
For diesel removal and installation procedures,
refer to the gas section of Fuel System/Fuel Delivery.
See Fuel Level Sending Unit/Sensor Removal/Instal-
lation.
14 - 68 FUEL DELIVERY - DIESELDR
FUEL INJECTION PUMP (Continued)

FUEL LINES
DESCRIPTION
Low-Pressure Lines
²the fuel supply line from fuel tank to fuel trans-
fer (lift) pump.
²the fuel return line back to fuel tank.
²the fuel drain manifold line at rear of cylinder
head.
²the fuel supply line from fuel filter to fuel injec-
tion pump.
High-Pressure Lines
²the fuel line from fuel injection pump to overflow
valve.
²the fuel line from fuel injection pump to fuel
rail.
²the 6 fuel lines from fuel rail up to injector con-
nector tubes
WARNING: HIGH-PRESSURE FUEL LINES DELIVER
DIESEL FUEL UNDER EXTREME PRESSURE FROM
THE INJECTION PUMP TO THE FUEL INJECTORS.
THIS MAY BE AS HIGH AS 160,000 KPA (23,206
PSI). USE EXTREME CAUTION WHEN INSPECTING
FOR HIGH-PRESSURE FUEL LEAKS. INSPECT FOR
HIGH-PRESSURE FUEL LEAKS WITH A SHEET OF
CARDBOARD. HIGH FUEL INJECTION PRESSURE
CAN CAUSE PERSONAL INJURY IF CONTACT IS
MADE WITH THE SKIN.
OPERATION
High-Pressure Lines
CAUTION: The high-pressure fuel lines must be
held securely in place in their holders. The lines
cannot contact each other or other components. Do
not attempt to weld high-pressure fuel lines or to
repair lines that are damaged. If lines are ever
kinked or bent, they must be replaced. Use only the
recommended lines when replacement of high-pres-
sure fuel line is necessary.
High-pressure fuel lines deliver fuel (under pres-
sure) of up to approximately 160,000 kPa (23,206
PSI) from the injection pump to the fuel injectors.
The lines expand and contract from the high-pres-
sure fuel pulses generated during the injection pro-
cess. All high-pressure fuel lines are of the same
length and inside diameter. Correct high-pressure
fuel line usage and installation is critical to smooth
engine operation.WARNING: USE EXTREME CAUTION WHEN
INSPECTING FOR HIGH-PRESSURE FUEL LEAKS.
INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH
A SHEET OF CARDBOARD. HIGH FUEL INJECTION
PRESSURE CAN CAUSE PERSONAL INJURY IF
CONTACT IS MADE WITH THE SKIN.
DIAGNOSIS AND TESTING - HIGH-PRESSURE
FUEL LINE LEAKS
High-pressure fuel line leaks can cause starting
problems and poor engine performance.
WARNING: DUE TO EXTREME FUEL PRESSURES
OF UP TO 160,000 kPa (23,206 PSI), USE EXTREME
CAUTION WHEN INSPECTING FOR HIGH-PRES-
SURE FUEL LEAKS. DO NOT GET YOUR HAND OR
A FINGER NEAR A SUSPECTED LEAK. INSPECT
FOR HIGH-PRESSURE FUEL LEAKS WITH A SHEET
OF CARDBOARD. HIGH FUEL INJECTION PRES-
SURE CAN CAUSE PERSONAL INJURY IF CON-
TACT IS MADE WITH THE SKIN.
Start the engine. Move the cardboard (Fig. 15) over
the suspected high-pressure fuel line leak, and check
for fuel spray onto the cardboard. If line is leaking,
retorque line. Replace damaged, restricted or leaking
high-pressure fuel lines with the correct replacement
line.
CAUTION: The high-pressure fuel lines must be
clamped securely in place in the holders. The lines
cannot contact each other or other components. Do
not attempt to weld high-pressure fuel lines or to
repair lines that are damaged. Only use the recom-
mended lines when replacement of high-pressure
fuel line is necessary.
REMOVAL
CAUTION: Cleanliness cannot be overemphasized
when handling or replacing diesel fuel system com-
ponents. 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 pos-
sible 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.
Cap or cover any open part after disassembly.
Before assembly, examine each part for dirt, grease
or other contaminants and clean if necessary. When
installing new parts, lubricate them with clean
engine oil or clean diesel fuel only.
DRFUEL DELIVERY - DIESEL 14 - 69

INSTALLATION
All high-pressure fuel lines are of the same length
and inside diameter. Correct high-pressure fuel line
usage and installation is critical to smooth engine
operation.
(1) Position fuel line support clamp to fuel line.
Install clamp nuts/bolts and tighten finger tight.
(2) Position proper fuel line to proper injector on
engine. Tighten fittings hand tight at both ends of
line.
(3) Tighten fuel lines at high pressure injector con-
nector to 30 N´m (22 lb. ft.).
(4) Tighten fuel lines at fuel rail to 30 N´m (22 lb.
ft.).
(5) Tighten clamp/support nuts and bolts.
(6) Install engine lifting bracket and bolt. Tighten
bolt to 77 N´m (56 lb.ft.).(7) If fuel line at either #1 or #2 cylinder has been
replaced, install intake manifold air heater elements
to top of intake manifold. Refer to Intake Air Heater
Removal / Installation for procedures.
(8) If fuel line at #6 cylinder has been replaced, tilt
metal bracket upward and tighten 2 bolts at rear of
cylinder head.
(9) Install remaining fuel line support clamps and
bracket bolts at intake manifold.
(10) Connect both negative battery cables to both
batteries.
(11) Prime fuel system. Refer to Fuel System
Priming.
(12) Check lines/fittings for leaks.
Fig. 18 HIGH PRESSURE FUEL LINES
1 - FUEL INJECTOR
2 - HIGH-PRESSURE LINE
3 - INJECTOR MOUNTING BOLTS
4 - FUEL INJECTOR RAIL5 - SEPARATE FITTING (TYPICAL)
6 - CONNECTOR TUBE RETAINER (FITTING)
7 - CONNECTOR TUBE
DRFUEL DELIVERY - DIESEL 14 - 71
FUEL LINES (Continued)