fig DODGE RAM 1500 1998 2.G Workshop Manual

(3) Remove APPS. Refer to Accelerator Pedal Posi-
tion Sensor (APPS) Removal / Installation.
(4) From inside vehicle, remove cable clip (Fig. 1).
(5) Remove cable housing from dash panel and
pull cable into engine compartment.
(6) Remove cable housing at APPS bracket by
pressing on release tab with a small screwdriver.To
prevent cable housing breakage, press on tab
only enough to release cable from APPS
bracket.
INSTALLATION
3.7L V-6
(1) Slide accelerator cable plastic mount into throt-
tle body mounting bracket. Continue sliding until
release tab (Fig. 34) is aligned to hole in mounting
bracket.
(2) Hold throttle in wide open position. While held
in this position, slide throttle cable pin (Fig. 33) 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.
4.7L V-8
(1) Slide accelerator cable plastic mount into
bracket. Continue sliding until tab (Fig. 36) 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.
Fig. 35 ACCELERATOR CABLE AT BELL CRANK -
4.7L V-8
1 - THROTTLE BODY
2 - SPEED CONTROL CABLE CONNECTOR
3 - OFF
4 - OFF
5 - ACCELERATOR CABLE CONNECTOR
6 - CABLE CAM
7 - BELLCRANK
Fig. 36 ACCELERATOR CABLE RELEASE TAB -
4.7L V-8
1 - ACCELERATOR CABLE
2 - PLASTIC CABLE MOUNT
3 - PRESS TAB FOR REMOVAL
4 - CABLE BRACKET
5 - SLIDE FOR REMOVAL
14 - 40 FUEL INJECTION - GASDR
THROTTLE CONTROL CABLE (Continued)

(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.
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.
The PCM supplies approximately 5 volts to the
TPS. The TPS output voltage (input signal to the
PCM) represents the throttle blade position. The
PCM receives an input signal voltage from the TPS.
This will vary in an approximate range of from .26
volts at minimum throttle opening (idle), to 4.49 volts
at wide open throttle. Along with inputs from other
sensors, the PCM uses the TPS input to determine
current engine operating conditions. In response to
engine operating conditions, the PCM will adjust fuel
injector pulse width and ignition timing.The PCM needs to identify the actions and position
of the throttle blade at all times. This information is
needed to assist in performing the following calcula-
tions:
²Ignition timing advance
²Fuel injection pulse-width
²Idle (learned value or minimum TPS)
²Off-idle (0.06 volt)
²Wide Open Throttle (WOT) open loop (2.608
volts above learned idle voltage)
²Deceleration fuel lean out
²Fuel cutoff during cranking at WOT (2.608 volts
above learned idle voltage)
²A/C WOT cutoff (certain automatic transmis-
sions only)
REMOVAL
3.7L V6
The Throttle Position Sensor (TPS) is mounted to
the throttle body (Fig. 37), or (Fig. 38).
(1) Remove air resonator tube at throttle body.
(2) Disconnect TPS electrical connector.
(3) Remove 2 TPS mounting screws.
(4) Remove TPS.
Fig. 37 TPS LOCATION - 3.7L V-6
1 - THROTTLE POSITION SENSOR (TPS)
2 - MOUNTING SCREWS
3 - IDLE AIR CONTROL MOTOR (IAC)
4 - MOUNTING SCREWS
DRFUEL INJECTION - GAS 14 - 41
THROTTLE CONTROL CABLE (Continued)

4.7L V-8
The TPS is located on the throttle body (Fig. 39).
(1) Remove air duct and tube at throttle body.
(2) Disconnect TPS electrical connector.
(3) Remove two TPS mounting bolts (screws) (Fig.
39).
(4) Remove TPS from throttle body.
5.7L V-8
The 5.7L V-8 engine does not use a separate Throt-
tle Position Sensor (TPS) on the throttle body.
Fig. 38 TPS INSTALLATION - 3.7 V-6
1 - THROTTLE BODY
2 - TPS
3 - THROTTLE BODY SHAFT
4 - SOCKET LOCATING TANGS
Fig. 39 TPS LOCATION - 4.7L
1 - THROTTLE BODY
2 - TPS
3 - IAC MOTOR
4 - IAT SENSOR
5 - MOUNTING SCREWS
14 - 42 FUEL INJECTION - GASDR
THROTTLE POSITION SENSOR (Continued)

INSTALLATION
3.7L V-6
The Throttle Position Sensor (TPS) is mounted to
the throttle body (Fig. 37).
The throttle shaft end of throttle body slides into a
socket in TPS (Fig. 40). 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. 41). 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.
(5) Install air duct/air box to throttle body.
Fig. 40 TPS INSTALLATION - 3.7L
1 - THROTTLE BODY
2 - TPS
3 - THROTTLE BODY SHAFT
4 - SOCKET LOCATING TANGS
Fig. 41 TPS INSTALLATION - 4.7L
1 - THROTTLE BODY
2 - LOCATING TANGS
3 - THROTTLE POSITION SENSOR
4 - SOCKET
5 - THROTTLE SHAFT
DRFUEL INJECTION - GAS 14 - 43
THROTTLE POSITION SENSOR (Continued)

FUEL DELIVERY - DIESEL
DESCRIPTION - DIESEL FUEL SYSTEM
The fuel system used on the Cummins engine is an
electronically controlled, Bosch HPCR (High-Pressure
Common Rail) system. The HPCR system consists of
five main components:
²Electric Fuel Transfer (lift) Pump
²Fuel Pump/Gear Pump (attached to fuel injec-
tion pump)
²High-Pressure Fuel Injection Pump
²Fuel Injection Rail
²Fuel Injectors
Also to be considered as part of the overall fuel
system are:
²Accelerator Pedal
²Air Cleaner Housing/Element
²Fuel Drain Manifold (passage)
²Fuel Drain Valve (at filter)
²Fuel Filter/Water Separator
²Fuel Heater
²Fuel Heater Relay
²Fuel Level (gauge) Sending Unit
²Fuel Pressure Limiting Valve
²Fuel Tank
²Fuel Tank Module (containing fuel gauge send-
ing unit and separate fuel filter located at bottom of
tank module)
²Fuel Tank Filler/Vent Tube Assembly
²Fuel Tank Filler Tube Cap
²Fuel Tubes/Lines/Hoses
²High-Pressure Fuel Injector Lines
²In-Tank Fuel Filter (at bottom of fuel tank mod-
ule)
²Low-Pressure Fuel Supply Lines
²Low-Pressure Fuel Return Line
²Overflow Valve
²Quick-Connect Fuel Line Fittings
²Throttle Cable
²Water Draining (maintenance)
²Water-In-Fuel (WIF) Sensor
The fuel injection pump supplies high pressure to
the fuel rail independent of engine speed. This high
pressure fuel is then accumulated in the fuel rail.
High pressure fuel is constantly supplied to the injec-
tors by the fuel rail. The Engine Control Module
(ECM) controls the fueling and timing of the engine
by actuating 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
pump. The Fuel Pump/Gear Pump is a low-pressure
pump and produce pressures ranging from 551.5 kpa
(80 psi) to 1241 kpa (180) psi. Fuel then enters the
fuel injection pump. Low pressure fuel is then sup-
plied to the FCA (Fuel Control Actuator).
The FCA is an electronically controlled solenoid
valve. The ECM controls the amount of fuel that
enters the high-pressure pumping chambers by open-
ing and closing the FCA based on a demanded fuel
pressure. The FPS (Fuel Pressure Sensor) on the fuel
rail monitors the actual fuel pressure and provides it
as an input to the ECM. When the actuator is
opened, the maximum amount of fuel is being sup-
plied to the fuel injection pump. Any fuel that does
not enter the injection pump is directed to the over-
flow valve. The overflow valve regulates how much
excess fuel is used for lubrication of the pump and
how much is returned to the tank through the drain
manifold.
Fuel entering the injection pump is pressurized to
between 300-1600 bar (4351-23,206 psi) by three
radial pumping chambers. The pressurized fuel is
then supplied to the fuel rail.
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.
Certain fuel system components can be found in
(Fig. 1), or (Fig. 2).
DRFUEL DELIVERY - DIESEL 14 - 45

Fig. 1 DIESEL FUEL SYSTEM COMPONENTS
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 RETURN LINE CONNECTION (TO FUEL TANK)
3 - INTAKE MANIFOLD AIR HEATER/ELEMENTS 16 - FUEL DRAIN TUBE
4 - FUEL PRESSURE SENSOR 17 - OIL PRESSURE SWITCH
5 - FUEL PRESSURE LIMITING VALVE 18 - ENGINE CONTROL MODULE (ECM)
6 - HIGH-PRESSURE FUEL LINES 19 - FUEL INJECTION PUMP
7 - FUEL HEATER 20 - CRANKSHAFT POSITION (ENGINE SPEED) SENSOR
8 - HIGH-PRESSURE FUEL RAIL 21 - CAMSHAFT POSITION SENSOR (CMP)
9 - FUEL HEATER TEMPERATURE SENSOR (THERMOSTAT) 22 - FUEL CONTROL ACTUATOR (FCA)
10 - FUEL FILTER/WATER SEPARATOR 23 - CASCADE OVERFLOW VALVE
11 - FUEL TRANSFER (LIFT) PUMP
12 - FUEL DRAIN MANIFOLD (CYLINDER HEAD FUEL RETURN
LINE)
13 - DRAIN VALVE
14 - 46 FUEL DELIVERY - DIESELDR
FUEL DELIVERY - DIESEL (Continued)

STANDARD PROCEDURE
STANDARD PROCEDURES - WATER DRAINING
AT FUEL FILTER
Refer to Fuel Filter/Water Separator removal/in-
stallation for procedures.
STANDARD PROCEDURES - CLEANING FUEL
SYSTEM PARTS
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.
STANDARD PROCEDURE - FUEL SYSTEM
PRIMING
A certain amount of air becomes trapped in the
fuel system when fuel system components on the
supply and/or high-pressure side are serviced or
replaced. Fuel system priming is accomplished using
the electric fuel transfer (lift) pump.
Servicing or replacing fuel system components will
not require fuel system priming.
The fuel transfer (lift) pump is self-priming: When
the key is first turned on (without cranking engine),
the pump operates for approximately 1 to 2 second
and then shuts off. The pump will also operate for up
to 25 seconds after the starter is quickly engaged,
and then disengaged without allowing the engine to
start. The pump shuts off immediately if the key is
on and the engine stops running.
(1) Turn key to CRANK position and quickly
release key to ON position before engine starts. This
will operate fuel transfer pump for approximately 25
seconds.
(2) Crank engine. If the engine does not start after
25 seconds, turn key OFF. Repeat previous step until
engine starts.
(3) Fuel system priming is now completed.
(4) Attempt to start engine. If engine will not
start, proceed to following steps.When engine does
start, it may run erratically and be noisy for a
few minutes. This is a normal condition.
CAUTION: Do not engage the starter motor for more
than 30 seconds at a time. Allow two minutes
between cranking intervals.
(5) Perform previous fuel priming procedure steps
using fuel transfer pump. Be sure fuel is present at
fuel tank.
(6) Crank the engine for 30 seconds at a time to
allow fuel system to prime.
WARNING: THE FUEL INJECTION PUMP SUPPLIES
EXTREMELY HIGH FUEL PRESSURE TO EACH INDI-
VIDUAL INJECTOR THROUGH THE HIGH-PRES-
SURE LINES. FUEL UNDER THIS AMOUNT OF
PRESSURE CAN PENETRATE THE SKIN AND
CAUSE PERSONAL INJURY. WEAR SAFETY GOG-
GLES AND ADEQUATE PROTECTIVE CLOTHING.
DO NOT LOOSEN FUEL FITTINGS WHILE ENGINE
IS RUNNING.
WARNING: ENGINE MAY START WHILE CRANKING
STARTER MOTOR.
Fig. 2 FUEL INJECTORS
1 - SOLENOID CONNECTIONS
2 - ROCKER HOUSING
3 - FUEL INJECTOR
4 - PASSTHROUGH CONNECTOR
DRFUEL DELIVERY - DIESEL 14 - 47
FUEL DELIVERY - DIESEL (Continued)

FUEL FILTER / WATER
SEPARATOR
DESCRIPTION
The fuel filter/water separator assembly is located
on left side of engine above the starter motor. The
assembly also includes the fuel heater, 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 in the owners
manual for the recommended 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 the
side of fuel filter housing. 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, or
the owners manual for recommended fuel filter
replacement intervals.
Draining water from fuel filter/water separa-
tor housing:
The housing drain valve (Fig. 3) serves two pur-
poses. One is topartiallythe drain filter housing of
excess water. The other is tocompletelythe drain
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 the water-in-fuel warning lamp remains
illuminated. (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) is located at the bottom of
drain valve. Place drain pan under drain hose.
(2)With engine not running,rotate drain valve
handle counter-clockwise (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, rotate valve handle
clockwise (forward) to the 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. 4) using a socket.
Attach socket to large hex on top of lid (Fig. 4).
Rotate counter-clockwise for removal. Remove
o-ring. Discard 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).
(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).
(a) Remove fuel filter. See previous steps.
(b) Disconnect electrical connector.
(c) Remove two T-15 Torx head mounting screws
from fuel heater element.
(d) Remove fuel heater.
(8)Drain Valve Replacement:The drain valve
assembly is located on the side of the fuel filter hous-
ing (Fig. 3).
(a) Disconnect drain hose from the fuel drain
valve.
(b) Remove 4 drain valve mounting screws (T-15
Torx head).
(c) Remove drain valve from filter housing.
INSTALLATION
Refer to maintenance schedules for recommended
fuel filter replacement intervals.
(1) Thoroughly clean inside of filter housing, filter
cap and all related components.
(2)Fuel Filter:
(a)The engine has a self-priming low-pres-
sure fuel system. Refer to Standard Proce-
dures-Fuel System Priming.
ENGINE ROTATING (BARRING) TOOL - #7471B
(ALSO PART OF KIT #6860)
14 - 50 FUEL DELIVERY - DIESELDR
FUEL DELIVERY - DIESEL (Continued)

(b) Install new o-ring to canister lid and lubri-
cate o-ring with clean engine oil.
(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 oil to o-ring seal.
(c) Install sensor into housing.
(d) Tighten sensor to 2.5 N´m (25 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 (13 in. lbs.) torque.
(d) Connect electrical connector to fuel heater
thermostat.
(e) Install new filter cover O-ring onto fuel filter
housing cover and lubricate with clean engine 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).
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.
Fig. 3 FILTER HOUSING
1 - FILTER HOUSING
2 - FUEL HEATER AND THERMOSTAT
3 - FUEL HEATER MOUNTING SCREWS
4 - FUEL HEATER ELEC. CONNECTOR
5 - WIF SENSOR
6 - WIF SENSOR ELEC. CONNECTOR
7 - DRAIN HOSE
8 - DRAIN VALVE MOUNTING SCREWS
9 - DRAIN VALVE
Fig. 4 FILTER COVER (LID)
1 - FILTER COVER
2 - ATTACH SOCKET HERE
DRFUEL DELIVERY - DIESEL 14 - 51
FUEL FILTER / WATER SEPARATOR (Continued)

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).
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 the
fuel heater. The resistance value of the heater ele-
ment is less than 1 ohm (cold) and up to 1000 ohms
warm.
TESTING
(1) Disconnect electrical connector from thermostat
(Fig. 3).
Ambient temperature must be below the circuit
close temperature. If necessary, induce this ambient
temperature by placing ice packs on thermostat to
produce an effective ambient temperature below cir-
cuit close temperature.
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
heater. The heater can be checked at room tempera-
ture. Operating range is 0.3 - 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. 5). 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. 6). Refer to label under
PDC cover for relay location.
(1) Remove PDC cover.
(2) Remove relay from PDC.
Fig. 5 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 - 52 FUEL DELIVERY - DIESELDR
FUEL HEATER (Continued)