pump JEEP GRAND CHEROKEE 2003 WJ / 2.G Workshop Manual
[x] Cancel search | Manufacturer: JEEP, Model Year: 2003, Model line: GRAND CHEROKEE, Model: JEEP GRAND CHEROKEE 2003 WJ / 2.GPages: 2199, PDF Size: 76.01 MB
Page 1434 of 2199
(8) Connect fuel return and pressure lines to fuel
pump module fittings (Fig. 16). Refer to Quick-Con-
nect Fittings.
(9) Install fuel tank. Refer to Fuel Tank Installa-
tion.
FUEL RAIL
DESCRIPTION
DESCRIPTION - 4.7L
The fuel injector rail is used to mount the fuel
injectors to the engine. It is mounted to the intake
manifold (Fig. 20).
DESCRIPTION - 4.0L
The fuel injector rail is used to mount the fuel
injectors to the engine (Fig. 21). On the 4.0L 6±cylin-
der engine, afuel damperis located near the center
of the fuel rail (Fig. 21).
OPERATION
OPERATION - 4.7L
High pressure fuel from the fuel pump is routed to
the fuel rail. The fuel rail then supplies the neces-
sary fuel to each individual fuel injector.
A fuel pressure test port is located on the fuel rail
(Fig. 20). A quick-connect fitting with a safety latch
is used to attach the fuel line to the fuel rail.
The fuel rail is not repairable.
OPERATION - 4.0L
The fuel injector rail supplies the necessary fuel to
each individual fuel injector.
High pressure fuel from the fuel pump is routed to
the fuel rail. The fuel rail then supplies the neces-
sary fuel to each individual fuel injector.
The fuel damper is used only to help control fuel
pressure pulsations. These pulsations are the result
of the firing of the fuel injectors. It isnot usedas a
fuel pressure regulator. The fuel pressure regulator is
not mountedto the fuel rail on any engine. It is
located near the front of the fuel tank above the rear
axle. Refer to Fuel Filter/Fuel Pressure Regulator in
this group for information.
A fuel pressure test port is located on the fuel rail
(Fig. 21). A quick-connect fitting with a safety latch
is used to attach the fuel line to the fuel rail.
The fuel rail is not repairable.
REMOVAL
REMOVAL - 4.7L
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT PRESSURE EVEN WITH ENGINE OFF.
BEFORE SERVICING FUEL RAIL, FUEL SYSTEM
PRESSURE MUST BE RELEASED.
Fig. 20 Fuel Injector RailÐ4.7L V-8 Engine
1 - MOUNTING BOLTS (4)
2 - INJ.#7
3 - INJ.#5
4 - QUICK-CONNECT FITTING
5 - INJ.#3
6 - FUEL INJECTOR RAIL
7 - INJ.#1
8 - CONNECTOR TUBE
9 - INJ.#2
10 - INJ.#4
11 - INJ.#6
12 - INJ.#8
13 - PRESSURE TEST PORT CAP
WJFUEL DELIVERY 14 - 15
FUEL PUMP MODULE (Continued)
Page 1438 of 2199
(14) Install air tube (or duct) at top of throttle
body.
(15) Install fuel tank cap.
(16) Connect negative battery cable to battery.
(17) Start engine and check for fuel leaks.
FUEL TANK
DESCRIPTION
The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for place-
ment of the fuel pump module and certain ORVR
components.
OPERATION
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank con-
nections.
A fuel tank check valve(s) is mounted into the top
of the fuel tank (or pump module). Refer to Fuel
Tank Check Valve for additional information.
An evaporation control system is connected to the
check valve(s) to reduce emissions of fuel vapors into
the atmosphere. When fuel evaporates from the fuel
tank, vapors pass through vent hoses or tubes to a
charcoal canister where they are temporarily held.
When the engine is running, the vapors are drawn
into the intake manifold. Certain models are also
equipped with a self-diagnosing system using a Leak
Detection Pump (LDP). Refer to Emission Control
System for additional information.
Refer to ORVR for On-Board Refueling Vapor
Recovery system information.
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT FUEL PRESSURE EVEN WITH ENGINE OFF.
PRESSURE MUST BE RELEASED BEFORE SERVIC-
ING FUEL TANK.
Two different procedures may be used to drain fuel
tank (through ORVR control valve opening at top of
fuel tank, or using DRB scan tool). The quickest is
draining through ORVR control valve opening at top
of fuel tank (Fig. 26).
As an alternative procedure, the electric fuel pump
may be activated allowing tank to be drained at fuel
rail connection. Refer to DRB scan tool for fuel pump
activation procedures. Before disconnecting fuel line
at fuel rail, release fuel pressure. Refer to the Fuel
System Pressure Release Procedure for procedures.
Attach end of Special Adapter Hose Tool number
6539 at fuel rail disconnection. Position opposite end
of 6539 to an approved gasoline draining station.Activate fuel pump with DRB and drain tank until
empty.
If electric fuel pump is not operating, tankMUST
be drained through ORVR control valve opening at
top of fuel tank (Fig. 26).
(1) Release fuel system pressure. Refer to Fuel
System Pressure Release Procedure.
(2) Disconnect negative battery cable at battery.
(3) Raise and support vehicle.
(4) Remove left rear wheel/tire.
CAUTION: HANDLE EVAP, LDP AND ORVR VAPOR /
VACUUM LINES VERY CAREFULLY. THESE LINES
AND HOSES MUST BE FIRMLY CONNECTED.
CHECK THE VAPOR/VACUUM LINES AT THE LDP,
LDP FILTER, EVAP CANISTER, EVAP CANISTER
PURGE SOLENOID AND ORVR COMPONENTS FOR
DAMAGE OR LEAKS. IF A LEAK IS PRESENT, A
DIAGNOSTIC TROUBLE CODE (DTC) MAY BE SET.
(5) Clean top of fuel tank at ORVR control valve
(Fig. 26) or (Fig. 27).
(6) Press release tab in direction of arrow in (Fig.
27) and remove ORVR control valve lock ring
(counter-clockwise). Lift up ORVR control slightly.
Using an approved gasoline draining station, drain
tank until empty through this opening.
(7) Remove stone shield behind left/rear wheel
(Fig. 28). Drill out plastic rivets for removal.
(8) Remove 3 LDP mounting bolts (Fig. 29).
(9) Remove support bracket brace bolt (Fig. 30).
(10) Loosen, but do not remove 2 support bracket
nuts at frame rail (Fig. 29).
(11) To separate and lower front section of two-
piece support bracket, remove 3 attaching bolts on
bottom of support bracket (Fig. 30). While lowering
support bracket, disconnect LDP wiring clip (Fig. 31).
(12) Remove hose clamp (Fig. 32) and remove fuel
fill hose from fuel fill tube.
(13) Cut and discard tie wrap from axle vent hose
(Fig. 32).
(14) Disconnect fuel vent hose from fuel vent tube
(Fig. 32).
(15) Disconnect ORVR hose elbow (Fig. 33) at top
of EVAP canister.
(16) Place hydraulic jack to bottom of fuel tank.
(17) Remove fuel tank-to-rear bumper fascia clips
(Fig. 34).
(18) Remove fuel tank heat shield mounting bolts
(Fig. 35).
CAUTION: To protect fuel tank from exhaust heat,
shield must re-installed after tank installation.
WARNING: PLACE SHOP TOWEL AROUND FUEL
LINES TO CATCH ANY EXCESS FUEL.
WJFUEL DELIVERY 14 - 19
FUEL RAIL (Continued)
Page 1439 of 2199
(19) Disconnect fuel return line at fuel filter/fuel
pressure regulator (Fig. 36). Refer to Quick-Connect
Fittings for procedures.
(20) Disconnect fuel pressure line at fuel filter/fuel
pressure regulator (Fig. 36). Refer to Quick-Connect
Fittings for procedures.
(21) Disconnect EVAP canister vent line near front
of tank (Fig. 36).
(22) Disconnect fuel pump module electrical con-
nector (pigtail harness) near front of tank (Fig. 36).
Harness connector is clipped to body.
(23) Remove left / front tank support bracket bolt
at frame (Fig. 37).
(24)WITHOUT TRAILER HITCH:Remove tank-
to-frame mounting bolts (Fig. 39). Remove rear tank
support bracket bolts at frame (Fig. 38). Carefully
lower tank until clear of vehicle. Place tank on floor.
(25)WITH TRAILER HITCH:Remove tank /
hitch mounting bolts (Fig. 40). Carefully lower tank
until clear of vehicle. Place tank on floor.
(26) If necessary, separate skid plate from fuel
tank by removing 2 fuel tank strap nuts (Fig. 39) and
remove 2 tank straps.
(27) If fuel pump module removal is necessary,
refer to Fuel Pump Module Removal/Installation.
(28) If hoses are to be removed at fuel tank end,
note painted alignment (indexing) markings on
hoses, and molded indexing tangs on tank before
removal. Remove hoses.
(29) If necessary, remove 3 fuel filler tube assem-
bly mounting bolts (Fig. 41) and remove fuel filler
tube.
INSTALLATION
CAUTION: HANDLE EVAP, LDP AND ORVR VAPOR /
VACUUM LINES VERY CAREFULLY. THESE LINES
AND HOSES MUST BE FIRMLY CONNECTED.
CHECK THE VAPOR/VACUUM LINES AT THE LDP,
LDP FILTER, EVAP CANISTER, EVAP CANISTER
PURGE SOLENOID AND ORVR COMPONENTS FOR
DAMAGE OR LEAKS. IF A LEAK IS PRESENT, A
DIAGNOSTIC TROUBLE CODE (DTC) MAY BE SET.
(1) If necessary, position fuel filler tube assembly
to body. Install 3 bolts and tighten to 2 N´m (15 in.
lbs.) torque.
(2) If necessary, connect quick-connect fittings to
fuel pump module.
(3) If fuel pump module is being installed, refer to
Fuel Pump Module Removal/Installation.
(4) Install fuel fill/vent hoses to tank fittings. To
prevent hoses from kinking, rotate each hose until
painted indexing mark on hose is aligned to molded
indexing tang on tank.
(5) Install hose clamps to hoses. Refer to Torque
Specifications.(6) If necessary, position fuel tank into skid plate.
Install 2 tank straps and 2 strap nuts (Fig. 39). Refer
to Torque Specifications.
(7) Position fuel tank / skid plate assembly to
hydraulic jack.
(8) Raise tank into position to frame.
(9)WITH TRAILER HITCH:Position trailer
hitch and tow hooks (Fig. 40) to bottom of fuel tank.
Install bolts and nuts loosely.
(10)WITHOUT TRAILER HITCH:Install 2 rear
tank support brackets and bolts (Fig. 38). Install
tank-to-frame bolts. Do not tighten bolts / nuts at
this time.
(11) Install 1 left / front tank support bracket and
bolts / nuts (Fig. 37). Do not tighten bolts / nuts at
this time.
(12) Be sure fuel tank is properly aligned to frame
and body. Tighten all tank, tow hook and trailer
hitch bolts / nuts except for 3 support brackets.
Tighten all 3 (2 rear and 1 left / front) support
bracket bolts / nuts last. Refer to Torque Specifica-
tions.
(13)
(14) Connect fuel pump module pigtail harness
electrical connector near front of tank.
(15) Connect both fuel lines to fuel filter/fuel pres-
sure regulator. Refer to Quick-Connect Fittings for
procedures.
(16) Connect EVAP hose near front of tank.
(17) Position rear axle vent hose and install new
tie strap (Fig. 32).
(18) Install heat shield nuts / bolts (Fig. 35). Refer
to Torque Specifications.
(19) Connect ORVR hose elbow (Fig. 33) to top of
EVAP canister.
(20) Connect fuel vent hose to fuel vent tube (Fig.
32).
(21) Install fuel fill hose and clamp to fuel fill tube
(Fig. 32).
(22) Install 3 LDP mounting bolts (Fig. 29).
(23) While raising support bracket, connect LDP
wiring clip (Fig. 31). Install front section of two-piece
support bracket to rear section with 3 attaching bolts
located on bottom of support bracket (Fig. 30).
(24) Install support bracket brace bolt (Fig. 30).
(25) Tighten 2 support bracket nuts at frame rail
(Fig. 29).
(26) Install fuel tank-to-rear bumper fascia clips
(Fig. 34).
(27) Using new plastic rivets, install stone shield
behind left/rear wheel (Fig. 28).
(28) Install left rear wheel/tire.
(29) Lower vehicle and connect negative battery
cable to battery.
(30) Fill tank with fuel and check for leaks.
14 - 20 FUEL DELIVERYWJ
FUEL TANK (Continued)
Page 1440 of 2199
Fig. 26 FUEL TANK AND COMPONENTS
1 - FUEL PUMP MODULE 9 - TANK SUPPORT BRACKET (SMALL/FRONT)
2 - MODULE LOCK RING 10 - MODULE PIGTAIL HARNESS
3 - TANK SUPPORT BRACKETS (REAR) 11 - FUEL SUPPLY (PRESSURE) LINE
4 - CHECK VALVE 12 - FUEL RETURN LINE
5 - FUEL FILL HOSE 13 - SKID PLATE
6 - ORVR COMPONENTS 14 - TANK STRAPS (2)
7 - ORVR CONTROL VALVE 15 - FUEL TANK
8 - CONTROL VALVE LOCK RING
WJFUEL DELIVERY 14 - 21
FUEL TANK (Continued)
Page 1446 of 2199
INLET FILTER
REMOVAL
The fuel pump inlet filter (strainer) is located on
the bottom of fuel pump module (Fig. 42). The fuel
pump module is located on top of fuel tank.
The fuel pump inlet filter (strainer) is located on
the bottom of fuel pump module (Fig. 42). The fuel
pump module is located on top of fuel tank.
(1) Remove fuel tank. Refer to Fuel Tank Removal/
Installation.
(2) Remove fuel pump module. Refer to Fuel Pump
Module Removal/Installation.
(3) Remove filter by prying from bottom of module
with 2 screwdrivers. Filter is snapped to module.
(4) Clean bottom of pump module.
INSTALLATION
The fuel pump inlet filter (strainer) is located on
the bottom of fuel pump module (Fig. 42). The fuel
pump module is located on top of fuel tank.
(1) Snap new filter to bottom of module.
(2) Install fuel pump module. Refer to Fuel Pump
Module Removal/Installation.
(3) Install fuel tank. Refer to Fuel Tank Removal/
Installation.
QUICK CONNECT FITTING
DESCRIPTION
Different types of quick-connect fittings are used to
attach various fuel system components, lines and tubes.
These are: a single-tab type, a two-tab type or a plastic
retainer ring type. Some are equipped with safety latch
clips. Some may require the use of a special tool for dis-
connection and removal. Refer to Quick-Connect Fit-
tings Removal/Installation for more information.
CAUTION: The interior components (o-rings, clips)
of quick-connect fittings are not serviced sepa-
rately, but new plastic spacers are available for
some types. If service parts are not available, do
not attempt to repair the damaged fitting or fuel line
(tube). If repair is necessary, replace the complete
fuel line (tube) assembly.
STANDARD PROCEDURE - QUICK-CONNECT
FITTINGS
Also refer to Fuel Tubes/Lines/Hoses and Clamps.
Different types of quick-connect fittings are used to
attach various fuel system components, lines and
tubes. These are: a single-tab type, a two-tab type or
a plastic retainer ring type. Safety latch clips are
used on certain components/lines. Certain fittings
may require use of a special tool for disconnection.
DISCONNECTING
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSE,
FITTING OR LINE, FUEL SYSTEM PRESSURE MUST
BE RELEASED. REFER TO FUEL SYSTEM PRES-
SURE RELEASE PROCEDURE.
CAUTION: The interior components (o-rings, spac-
ers) of some types of quick-connect fitting are not
serviced separately. If service parts are not avail-
able, do not attempt to repair a damaged fitting or
fuel line. If repair is necessary, replace complete
fuel line assembly.
(1) Perform fuel pressure release procedure. Refer
to Fuel Pressure Release Procedure.
(2) Disconnect negative battery cable from battery.
(3) Clean fitting of any foreign material before dis-
assembly.
(4)2±Button Type Fitting:This type of fitting is
equipped with a push-button located on each side of
quick-connect fitting (Fig. 43). Press on both buttons
simultaneously for removal. Special tools are not
required for disconnection.
Fig. 42 Fuel Pump Inlet Filter
1 - FUEL PUMP MODULE
2 - FUEL PUMP INLET FILTER
WJFUEL DELIVERY 14 - 27
Page 1450 of 2199
FUEL INJECTION
TABLE OF CONTENTS
page page
FUEL INJECTION
DIAGNOSIS AND TESTING
VISUAL INSPECTION..................32
SPECIFICATIONS
TORQUE - FUEL INJECTION.............39
ACCELERATOR PEDAL
REMOVAL.............................39
INSTALLATION.........................39
CRANKSHAFT POSITION SENSOR
DESCRIPTION
DESCRIPTION - 4.0L...................40
DESCRIPTION - 4.7L...................40
OPERATION
OPERATION - 4.0L....................40
OPERATION - 4.7L....................41
REMOVAL
REMOVAL - 4.0L......................41
REMOVAL - 4.7L......................41
INSTALLATION
INSTALLATION - 4.0L..................42
INSTALLATION - 4.7L..................43
FUEL INJECTOR
DESCRIPTION.........................43
OPERATION
OPERATION.........................43
OPERATION - PCM OUTPUT............43
DIAGNOSIS AND TESTING - FUEL INJECTOR . 44
REMOVAL.............................44
INSTALLATION.........................44
FUEL PUMP RELAY
DESCRIPTION.........................44
OPERATION...........................44
IDLE AIR CONTROL MOTOR
DESCRIPTION.........................44
OPERATION...........................44
REMOVAL
REMOVAL - 4.0L......................45
REMOVAL - 4.7L......................45
INSTALLATION
INSTALLATION - 4.0L..................46
INSTALLATION - 4.7L..................46
INTAKE AIR TEMPERATURE SENSOR
DESCRIPTION.........................46
OPERATION...........................46
REMOVAL
REMOVAL - 4.0L......................46
REMOVAL - 4.7L......................46
INSTALLATION
INSTALLATION - 4.0L..................47INSTALLATION - 4.7L..................47
MAP SENSOR
DESCRIPTION
DESCRIPTION........................48
DESCRIPTION - 4.7L...................48
OPERATION...........................48
REMOVAL
REMOVAL - 4.0L......................48
REMOVAL - 4.7L......................49
INSTALLATION
INSTALLATION - 4.0L..................49
INSTALLATION - 4.7L..................49
O2S HEATER RELAY
DESCRIPTION.........................49
OPERATION...........................49
REMOVAL.............................50
INSTALLATION.........................50
O2S SENSOR
DESCRIPTION.........................50
OPERATION...........................50
REMOVAL.............................51
INSTALLATION.........................51
THROTTLE BODY
DESCRIPTION.........................52
OPERATION...........................52
REMOVAL
REMOVAL - 4.0L......................52
REMOVAL - 4.7L......................53
INSTALLATION
INSTALLATION - 4.0L..................53
INSTALLATION - 4.7L..................54
THROTTLE CONTROL CABLE
REMOVAL
REMOVAL - 4.0L......................54
REMOVAL - 4.7L......................55
INSTALLATION
INSTALLATION ± 4.0L..................55
INSTALLATION - 4.7L..................56
THROTTLE POSITION SENSOR
DESCRIPTION.........................56
OPERATION...........................56
REMOVAL
REMOVAL - 4.0L......................57
REMOVAL - 4.7L......................57
INSTALLATION
INSTALLATION - 4.0L..................58
INSTALLATION - 4.7L..................58
WJFUEL INJECTION 14 - 31
Page 1451 of 2199
FUEL INJECTION
DIAGNOSIS AND TESTING
VISUAL INSPECTION
A visual inspection for loose, disconnected or incor-
rectly routed wires, vacuum lines and hoses should
be made. This should be done before attempting to
diagnose or service the fuel injection system. A visual
check will help spot these faults and save unneces-
sary test and diagnostic time. A thorough visual
inspection will include the following checks:
(1) Verify three 32±way electrical connectors are
fully inserted into connector of Powertrain Control
Module (PCM) (Fig. 1).
(2) Inspect battery cable connections. Be sure they
are clean and tight.
(3) Inspect fuel pump relay and air conditioning
compressor clutch relay (if equipped). Inspect ASD
and oxygen sensor heater relay connections. Inspect
starter motor relay connections. Inspect relays for
signs of physical damage and corrosion. The relays
are located in the Power Distribution Center (PDC)
(Fig. 2). Refer to label on PDC cover for relay loca-
tion.
(4) Inspect ignition coil connections (Fig. 3)or (Fig.
4).
(5) Verify camshaft position sensor wire connector
is firmly connected (Fig. 5) or (Fig. 6).
(6) Verify crankshaft position sensor wire connec-
tor is firmly connected (Fig. 7) or (Fig. 8).
Fig. 1 Powertrain Control Module (PCM) Location
1 - PCM
2 - COOLANT TANK
Fig. 2 Power Distribution Center (PDC) Location
1 - POWER DISTRIBUTION CENTER (PDC)
2 - BATTERY
Fig. 3 Ignition Coil ConnectorÐ4.0L Engine
1 - REAR OF VALVE COVER
2 - COIL RAIL
3 - COIL CONNECTOR
4 - RELEASE LOCK
5 - SLIDE TAB
14 - 32 FUEL INJECTIONWJ
Page 1457 of 2199
(23) Inspect for pinched or leaking fuel tubes/lines.
Inspect for pinched, cracked or leaking fuel hoses.
(24) Inspect for exhaust system restrictions such
as pinched exhaust pipes, collapsed muffler or
plugged catalytic convertor.
(25) If equipped with automatic transmission, ver-
ify electrical harness is firmly connected to park/neu-
tral switch and to transmission components.
(26) Verify fuel pump module pigtail harness elec-
trical connector (Fig. 15) is firmly connected to body
harness connector.
(27) Inspect fuel line harness (from fuel pump
module) at fuel filter/fuel pressure regulator (Fig. 15)
for chaffing, cracks or leaks.
(28) Verify battery cable and solenoid feed wire
connections to starter solenoid are tight and clean.
(29) Inspect for chaffed wires or wires rubbing up
against other components.
(30) Inspect for chaffed vacuum lines or lines rub-
bing up against other components.
Fig. 15 Fuel Filter/Fuel Pressure Regulator Location
1 - FUEL RETURN LINE
2 - FUEL SUPPLY LINE (TO FUEL RAIL)
3 - FUEL FILTER/FUEL PRESSURE REGULATOR
4 - FUEL PRESSURE LINE
5 - REAR AXLE
6 - ELEC. CONNECTOR
7 - EVAP LINE
14 - 38 FUEL INJECTIONWJ
FUEL INJECTION (Continued)
Page 1463 of 2199
The PCM determines injector on-time (pulse width)
based on various inputs.
DIAGNOSIS AND TESTING - FUEL INJECTOR
To perform a complete test of the fuel injectors and
their circuitry, use the DRB scan tool and refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the injector only, refer to the following:
Disconnect the fuel injector wire harness connector
from the injector. The injector is equipped with 2
electrical terminals (pins). Place an ohmmeter across
the terminals. Resistance reading should be approxi-
mately 12 ohms 1.2 ohms at 20ÉC (68ÉF).
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT PRESSURE EVEN WITH ENGINE OFF.
BEFORE SERVICING FUEL INJECTOR(S), FUEL
SYSTEM PRESSURE MUST BE RELEASED.
To remove one or more fuel injectors, the fuel rail
assembly must be removed from engine.
(1) Perform Fuel System Pressure Release Proce-
dure.
(2) Remove fuel injector rail. Refer to Fuel Injector
Rail Removal/Installation.
(3) Remove clip(s) retaining injector(s) to fuel rail
(Fig. 25).
(4) Remove injector(s) from fuel rail.
INSTALLATION
(1) Apply a small amount of engine oil to each fuel
injector o-ring. This will help in fuel rail installation.
(2) Install injector(s) and injector clip(s) to fuel
rail.
(3) Install fuel rail assembly. Refer to Fuel Injector
Rail Removal/Installation.
(4) Start engine and check for leaks.
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.
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.Fig. 25 Fuel Injector MountingÐTypical (4.7L V-8
Engine Shown)
1 - INLET FITTING
2 - FUEL INJECTOR RAIL
3 - CLIP
4 - FUEL INJECTOR
14 - 44 FUEL INJECTIONWJ
FUEL INJECTOR (Continued)
Page 1478 of 2199
STEERING
TABLE OF CONTENTS
page page
STEERING
DESCRIPTION - POWER STEERING SYSTEM . . 1
OPERATION - POWER STEERING SYSTEM . . . 1
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - POWER
STEERING SYSTEM....................2
DIAGNOSIS AND TESTING - STEERING
FLOW AND PRESSURE.................4DIAGNOSIS AND TESTING - 4.7L -
HYDRAULIC..........................5
COLUMN...............................7
GEAR.................................16
LINKAGE..............................26
PUMP.................................31
STEERING
DESCRIPTION - POWER STEERING SYSTEM
The power steering pump (Fig. 1) is a constant
flow rate and displacement vane type pump. The
pump reservoir is attached to the pump body. The
pump is connected to the steering by the pressure
and return hoses. The steering gear (Fig. 1) used is a
recirculating ball type gear. A tilt and non-tilt column
provide steering input.
The power steering system consists of:
OPERATION - POWER STEERING SYSTEM
The rack piston balls act as a rolling thread
between the worm shaft and rack piston. The worm
shaft is supported by a thrust bearing at the lower
end and a bearing assembly at the upper end. When
the worm shaft is turned from input from the steer-
ing column the rack piston moves. The rack piston
teeth mesh with the pitman shaft. Turning the worm
shaft turns the pitman shaft, which moves the steer-
ing linkage.
Fig. 1 POWER STEERING GEAR & PUMP 4.0L
1 - STEERING GEAR
2 - PRESSURE HOSE
3 - PUMP
4 - RETURN HOSE
5 - RESERVOIR
WJSTEERING 19 - 1