fuel pressure JEEP XJ 1995 Service And Service Manual

INSTALLATION
(1) Install the muffler onto the catalytic converter
outlet. Ensure that the locator on the converter
aligns with the notch on the muffler, if so equipped.
Install the clamp and tighten the nuts finger tight.
(2) Install the exhaust tailpipe into the muffler
outlet. Ensure that the locator on the exhaust
tailpipe aligns with the notch on the muffler, if so
equipped. Install the clamp and tighten the nuts fin-
ger tight.
(3) Install the front exhaust tailpipe supports and
the rear exhaust tailpipe hanger. Ensure that the ex-
haust tailpipe has sufficient clearance from the floor
pan and shields.
(4) Tighten the nuts on the muffler-to-catalytic
converter and the muffler-to-exhaust tailpipe clamps
to 61 Nzm (45 ft. lbs.) torque.
(5) Lower the vehicle.
(6) Start the engine and inspect for exhaust leaks
and contact with the body panels and shields.
ENGINE EXHAUST MANIFOLDÐ2.5L ENGINE
REMOVAL
(1) Disconnect the battery negative cable.
(2) Remove all components attached to the intake
manifold.
(3) Raise the vehicle.
(4) Disconnect the exhaust pipe from the engine
exhaust manifold.
(5) Lower the vehicle.
(6) Remove fasteners 2 through 5 and remove the
intake manifold (Fig. 11).
(7) Remove fasteners 1, 6 and 7 and remove the
engine exhaust manifold (Fig. 11).
CLEANING
Clean the intake and engine exhaust manifolds and
cylinder head mating surfaces.DO NOT allow for-eign material to enter either the intake mani-
fold or the ports in the cylinder head.
INSTALLATION
(1) Install a new intake manifold gasket over the
alignment dowels on the cylinder head.
(2) Install the engine exhaust manifold assembly.
Exhaust manifold must be centrally located
over the end studs and spacer (Fig. 11).
(3) Tighten bolt No.1 to 41 Nzm (30 ft. lbs.) torque
(Fig. 11).
(4) Install the intake manifold on the cylinder
head dowels (Fig. 11).
(5) Install bolts 2 through 5 (Fig. 11). Tighten
these bolts to 31 Nzm (23 ft. lbs.) torque.
(6) Install new engine exhaust manifold spacers
over the engine exhaust manifold mounting studs in
the cylinder head (Fig. 11).
(7) Tighten nuts 6 and 7 to 31 Nzm (23 ft. lbs.)
torque (Fig. 11).
(8) Install all components to the intake manifold.
(9) Raise the vehicle.
(10) Connect the exhaust pipe to the engine ex-
haust manifold. Tighten the bolts to 31 Nzm (23 ft.
lbs.) torque.
(11) Lower the vehicle.
(12) Connect the battery negative cable.
(13) Start the engine and check for leaks.
ENGINE EXHAUST MANIFOLDÐ4.0L ENGINE
The intake and engine exhaust manifolds on the
4.0L engine must be removed and installed together.
The manifolds use a common gasket at the cylinder
head.
Refer to Intake ManifoldÐ4.0L Engine in this sec-
tion for the proper removal and installation proce-
dures.
INTAKE MANIFOLDÐ2.5L ENGINE
REMOVAL
(1) Disconnect the battery negative cable.
(2) Remove the air inlet hose from the throttle
body and air cleaner.
(3) Loosen the accessory drive belt tension and re-
move the belt from the power steering pump.
(4) Remove the power steering pump and brackets
from the water pump and intake manifold. Support
power steering pump and bracket with mechanics
wire attached to the radiator upper crossmember.
(5) Remove the fuel tank filler cap to relieve the
fuel tank pressure.
(6) Install the fuel tank filler cap.
(7) Disconnect fuel supply and return tube from
the fuel rail (refer to Group 14, Fuel System - Quick
Connect Fittings).
(8) Disconnect the accelerator cable from the throt-
tle body and the holddown bracket.
Fig. 11 Intake/Engine Exhaust Manifold Installation
(2.5L Engine)
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 7

CAUTION: When disconnecting the cruise control
connector at the throttle body, DO NOT pry the con-
nector off with pliers or screwdriver. Use finger
pressure only. Prying the connector off could break
it.
(9) Disconnect the electrical connectors. Pull the
harnesses away from the manifold.
²The throttle position sensor.
²The idle speed control motor.
²The coolant temperature sensor at the thermostat.
²The manifold air temperature sensor at the intake
manifold.
²The fuel injectors.
²The oxygen sensor.
(10) Disconnect the crankcase ventilation (CCV)
vacuum hose and manifold absolute pressure (MAP)
sensor vacuum hose connector at the intake mani-
fold.
(11) Disconnect vacuum hose from vacuum port on
the intake manifold.
(12) Disconnect CCV hose at the cylinder head
cover (Fig. 12).
(13) Remove the molded vacuum harness.
(14) Disconnect the vacuum brake booster hose at
the intake manifold.
(15) Remove bolts 2 through 5 securing the intake
manifold to the cylinder head (Fig. 11). Slightly
loosen bolt No.1 and nuts 6 and 7.
(16) Remove the intake manifold and gaskets.
Drain the coolant from the manifold.
CLEANING
Clean the intake manifold and cylinder head mat-
ing surfaces.DO NOT allow foreign material to
enter either the intake manifold or the ports in
the cylinder head.
INSTALLATION
(1) Install the new intake manifold gasket over the
locating dowels.
(2) Position the manifold in place and finger
tighten the mounting bolts.
(3) Tighten the fasteners in sequence and to the
specified torque (Fig. 11).
²Fastener No.1ÐTighten to 41 Nzm (30 ft. lbs.)
torque.
²Fasteners Nos.2 through 7ÐTighten to 31 Nzm (23
ft. lbs.) torque.
(4) Connect the fuel return and supply tube to the
connector next to the fuel rail. Push them into the
fitting until a click is heard. Verify that the connec-
tions are complete.
²First, ensure only the retainer tabs protrude from
the connectors.
²Second, pull out on the fuel tubes to ensure they
are locked in place.
(5) Connect the molded vacuum hoses to the vac-
uum port on the intake manifold and the cylinder
head cover.
(6) Connect the electrical connectors.
²The throttle position sensor.
²The automatic idle speed control motor.
²The coolant temperature sensor at the thermostat
housing.
²The fuel injectors.
²The air manifold temperature sensor.
²The oxygen sensor.
(7) Connect the CCV vacuum hose and MAP sen-
sor vacuum hose connectors to the throttle body.
(8) Install the power steering pump and bracket
assembly to the water pump and intake manifold.
(9) Connect the accelerator cable and cruise control
cable to the holddown bracket and the throttle arm.
CAUTION: Ensure that the accessory drive belt is
routed correctly. Failure to do so can cause the wa-
ter pump to turn in the opposite direction resulting
in engine overheating. Refer to Group 7, Cooling
System for the proper procedure.
(10) Tension the accessory drive belt. Refer to
Group 7, Cooling System for the proper procedure.
(11) Connect the air inlet hose to the throttle body
and the air cleaner.
(12) Connect the battery negative cable.
(13) Start the engine and check for leaks.
INTAKE MANIFOLDÐ4.0L ENGINE
The intake and engine exhaust manifolds on the
4.0L engine must be removed and installed together.
The two manifolds use a common gasket at the cyl-
inder head.
REMOVAL
(1) Disconnect the battery negative cable.
Fig. 12 Crankcase Ventilation (CCV) Hose (2.5L
Engine)
11 - 8 EXHAUST SYSTEM AND INTAKE MANIFOLDJ

(2) Remove air cleaner inlet hose from throttle
plate assembly.
(3) Remove the air cleaner assembly.
(4) Remove the throttle cable, cruise control cable
(if equipped) and the transmission line pressure ca-
ble.
(5) Disconnect all electrical connectors on the in-
take manifold.
(6) Disconnect and remove the fuel supply and re-
turn lines from the fuel rail assembly (refer to Group
14, Fuel System).
(7) Loosen the accessory drive belt (refer to Group
7, Cooling System). Loosen the tensioner.
(8) Remove the power steering pump and bracket
from the intake manifold and set aside.
(9) Remove the fuel rail and injectors (refer to
Group 14, Fuel System).
(10) Raise the vehicle.
(11) Disconnect the exhaust pipe from the engine
exhaust manifold. Discard the seal.
(12) Lower the vehicle.
(13) Remove the intake manifold and engine ex-
haust manifold.
CLEANING
Clean the mating surfaces of the cylinder head and
the manifold if the original manifold is to be in-
stalled.
If the manifold is being replaced, ensure all the fit-
ting, etc. are transferred to the replacement mani-
fold.
INSTALLATION
(1) Install a new exhaust/intake manifold gasket
over the alignment dowels on the cylinder head.
(2) Position the engine exhaust manifold to the cyl-
inder head. Install fastener No.3 and finger tighten
at this time (Fig. 13).
(3) Install intake manifold on the cylinder head
dowels.
(4) Install washers and fasteners Nos.1, 2, 4, 5, 8,
9, 10 and 11 (Fig. 13).
(5) Install washers and fasteners Nos.6 and 7 (Fig.
13).
(6) Tighten the fasteners in sequence and to the
specified torque (Fig. 13).
²Fasteners Nos.1 through 5ÐTighten to 33 Nzm (24
ft. lbs.) torque.
²Fasteners Nos.6 and 7ÐTighten to 31 Nzm (23 ft.
lbs.) torque.²Fasteners Nos.8 through 11ÐTighten to 33 Nzm
(24 ft. lbs.) torque.
(7) Install the fuel rail and injectors.
(8) Install the power steering pump and bracket to
the intake manifold. Tighten the belt to specification.
Refer to Group 7, Cooling System for the proper pro-
cedures.
(9) Install the fuel supply and return lines to the
fuel rail assembly.Before connecting the fuel
lines to the fuel rail replace the O-rings in the
quick-connect fuel line couplings.Refer to Group
14, Fuel System for the proper procedure.
(10) Connect all electrical connections on the in-
take manifold.
(11) Connect the vacuum connector on the intake
manifold and install it in the bracket.
(12) Install throttle cable, cruise control cable (if
equipped).
(13) Install the transmission line pressure cable (if
equipped). Refer to Group 21, Transmission for the
adjustment procedures.
(14) Install air cleaner assembly.
(15) Connect air inlet hose to the throttle plate as-
sembly.
(16) Raise the vehicle on a side mounted hoist.
(17) Using a new seal, connect the exhaust pipe to
the engine exhaust manifold. Tighten the bolts to 31
Nzm (23 ft. lbs.) torque.
(18) Lower the vehicle.
(19) Connect the battery negative cable.
(20) Start the engine and check for leaks.
Fig. 13 Intake/Engine Exhaust Manifold Installation
(4.0L Engine)
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 9

FUEL SYSTEM
CONTENTS
page page
ACCELERATOR PEDAL AND THROTTLE CABLE.17
FUEL DELIVERY SYSTEM.................. 3
FUEL TANKS........................... 13
GENERAL INFORMATION.................. 1
MULTI-PORT FUEL INJECTION (MFI)Ð
COMPONENT DESCRIPTION/SYSTEMOPERATION.......................... 19
MULTI-PORT FUEL INJECTION (MFI)Ð
COMPONENT REMOVAL/INSTALLATION.... 58
MULTI-PORT FUEL INJECTION (MFI)Ð
GENERAL DIAGNOSIS.................. 35
SPECIFICATIONS........................ 67
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation
(XJ or YJ) or by the particular vehicle nameplate. A
chart showing a breakdown of the alphabetical desig-
nations is included in the Introduction section at the
beginning of this manual.
TheFuel Systemconsists of: the fuel tank, an
electric (fuel tank mounted) fuel pump and a fuel fil-
ter. It also consists of fuel tubes/lines/hoses, vacuum
hoses, throttle body and fuel injectors.
TheFuel Delivery Systemconsists of: the electric
fuel pump, fuel filter, fuel tubes/lines/hoses, fuel rail,
fuel injectors and fuel pressure regulator.
AFuel Return Systemis used on all vehicles.
The system consists of: the fuel tubes/lines/hoses that
route fuel back to the fuel tank.
TheFuel Tank Assemblyconsists of: the fuel
tank, filler tube, fuel fill and vent hoses, fuel gauge
sending unit/electric fuel pump module, a pressure
relief/rollover valve and a pressure-vacuum filler cap.
Also to be considered part of the fuel system is the
Evaporation Control System.This is designed to
reduce the emission of fuel vapors into the atmo-
sphere. The description and function of the Evapora-
tive Control System is found in Group 25, Emission
Control Systems.
FUEL USAGE STATEMENT
Your vehicle was designed to meet all emission reg-
ulations and provide excellent fuel economy using
high quality unleaded gasoline. Only use unleaded
gasolines having a minimum posted octane of 87.
If your vehicle develops occasional light spark
knock (ping) at low engine speeds, this is not harm-
ful. However,continued heavy knock at high
speeds can cause damage and should be re-
ported to your dealer immediately.Engine dam-
age as a result of heavy knock operation may not becovered by the new vehicle warranty.
In addition to using unleaded gasoline with the
proper octane rating,those that contain deter-
gents, corrosion and stability additives are rec-
ommended.Using gasolines that have these
additives will help improve fuel economy, reduce
emissions and maintain vehicle performance.
Poor quality gasolinecan cause problems such
as hard starting, stalling and stumble. If you experi-
ence these problems, use another brand of gasoline
before considering service for the vehicle.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with
materials that contain oxygen such as alcohol, MTBE
and ETBE. The type and amount of oxygenate used
in the blend is important. The following are generally
used in gasoline blends:
ETHANOL
Ethanol (Ethyl or Grain Alcohol) properly blended,
is used as a mixture of 10 percent ethanol and 90
percent gasoline.Gasoline with ethanol may be
used in your vehicle.
METHANOL
CAUTION: DO NOT USE GASOLINES CONTAINING
METHANOL.Use of methanol/gasoline blends may re-
sult in starting and driveability problems. In addition,
damage may be done to critical fuel system compo-
nents.
Methanol (Methyl or Wood Alcohol) is used in a va-
riety of concentrations blended with unleaded gaso-
JFUEL SYSTEM 14 - 1

FUEL DELIVERY SYSTEM
INDEX
page page
Fuel Filter................................ 9
Fuel Pressure Leak Down Test................ 8
Fuel Pressure Release Procedure.............. 6
Fuel Pump Capacity Test.................... 7
Fuel Pump Electrical Control.................. 5Fuel Pump Module......................... 3
Fuel System Pressure Test................... 6
Fuel Tubes/Lines/Hoses and Clamps............ 9
Quick-Connect Fittings..................... 10
FUEL PUMP MODULE
The fuel pump module is installed in the top of the
fuel tank. The fuel pump module contains the follow-
ing components:
²Electric fuel pump
²Fuel pump reservoir
²In-tank fuel filter
²Fuel gauge sending unit
²Fuel supply and return tube connections
The fuel pump used on all vehicles is a turbine
type pump. It is driven by a permanent magnet 12
volt electric motor that is immersed in the fuel tank.
The electrical pump is integral with the fuel sender
unit. The pump/sender assembly is installed inside
the fuel tank.
The fuel pump has a check valve at the outlet end
that consists of a ball held against a seat by force ap-
plied from a spring. When the pump is operating,
fuel pressure overcomes spring pressure and forces
the ball off its seat, allowing fuel to flow. When the
pump is not operating, spring pressure forces the ball
back against the seat preventing fuel backflow
through the pump.
Fuel system pressure is maintained at approxi-
mately 214 kPa (31 psi). This is when the pump is
operating and vacuum is supplied to the fuel pres-
sure regulator. If vacuum is not supplied to the pres-
sure regulator, fuel pressure will be approximately
55-69 kPa (8-10 psi) higher. This may be due to a
broken or clogged vacuum line. When the fuel pump
is not operating, fuel system pressure of 131-269 kPa
(19-39 psi) is maintained for approximately 2 to 6
hours. This is done by the fuel pump outlet check
valve and the vacuum assisted fuel pressure regula-
tor.
REMOVALÐXJ MODELS
The fuel pump/gauge sender unit assembly can be
removed from the fuel tank without removing the
tank from the vehicle.
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING THE FUEL PUMP MODULE,
THE FUEL SYSTEM PRESSURE MUST BE RE-LEASED. REFER TO THE FUEL PRESSURE RE-
LEASE PROCEDURE IN THIS GROUP.
WARNING: EXTINGUISH ALL TOBACCO SMOKING
PRODUCTS BEFORE SERVICING THE FUEL SYS-
TEM. KEEP OPEN FLAME AWAY FROM FUEL SYS-
TEM COMPONENTS.
(1) Remove fuel filler cap. Perform the Fuel Pres-
sure Release Procedure as outlined in this group.
(2) Disconnect negative battery cable.
(3) Using an approved portable gasoline siphon/
storage tank, drain fuel tank until fuel level is below
one quarter (1/4) full.
(4) Raise and support vehicle.
WARNING: WRAP SHOP TOWELS AROUND FUEL
HOSES TO ABSORB ANY FUEL SPILLAGE DURING
FUEL TANK REMOVAL.
(5) Disconnect fuel vent supply and return tubes
from fittings on fuel pump module.
(6) Disconnect fuel pump module electrical harness
connector from main harness.
(7) Using a brass punch and hammer, remove fuel
pump module lock ring by carefully tapping it coun-
terclockwise (Fig. 1).
Fig. 1 Removing Lock RingÐXJ ModelsÐTypical
JFUEL DELIVERY SYSTEM 14 - 3

(8) Remove fuel pump module and O-ring seal.
Discard old O-ring and fuel pump module inlet filter.
DISASSEMBLYÐXJ MODELS
(1) Remove and discard fuel pump inlet filter.
The wire terminals to the fuel pump motor are dif-
ferent in size and cannot be connected to the wrong
terminal.
(2) Disconnect fuel pump terminal wires.
(3) Remove fuel pump outlet hose and clamp. Re-
place the hose if it shows any signs of fatigue or fail-
ure.
(4) Remove fuel pump top mounting bracket nut.
Remove fuel pump (Fig. 2).
ASSEMBLYÐXJ MODELS
Whenever the fuel pump is replaced, the fuel pump
inlet filter (sock) must also be replaced.
(1) Place fuel pump top mounting bracket over top
of pump.
(2) Position fuel pump into lower bracket. Slide
stud of top bracket through hole in fuel pump side
bracket. Tighten fuel pump top mounting nut.
(3) Install new fuel pump outlet hose. Secure with
new clamps.
(4) Connect wire terminals to motor.
(5) Install new fuel pump inlet filter.
INSTALLATIONÐXJ MODELS
Whenever the fuel pump is replaced, the fuel
pump inlet filter must also be replaced.
(1) Install new fuel pump inlet filter onto fuel
pump.(2) Install fuel pump module assembly and new O-
ring seal. The rubber stopper on the end of the fuel
return tube of the assembly must be inserted into the
cup in the fuel tank reservoir (Fig. 3).
(3) Using a brass punch and a hammer, install lock
ring. Carefully tap lock ring clockwise until it seats
against stop on fuel tank.
(4) Connect fuel supply and return hoses to fittings
on fuel pump module. Tighten hose clamps.
(5) Connect fuel pump module electrical harness
connector to main harness connector.
(6) Lower vehicle.
(7) Fill fuel tank. Install fuel tank cap.
(8) Connect negative battery cable.
(9) Start vehicle and inspect for leaks.
REMOVALÐYJ MODELS
The fuel tank must be removed to remove the fuel
pump module.
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING THE FUEL PUMP MODULE,
THE FUEL SYSTEM PRESSURE MUST BE RE-
LEASED. REFER TO THE FUEL PRESSURE RE-
LEASE PROCEDURE IN THIS GROUP.
WARNING: EXTINGUISH ALL TOBACCO SMOKING
PRODUCTS BEFORE SERVICING THE FUEL SYS-
TEM. KEEP OPEN FLAME AWAY FROM FUEL SYS-
TEM COMPONENTS.
(1) Remove negative battery cable.
Fig. 2 Fuel Pump ModuleÐXJ ModelsÐ
Disassemble/Assemble
Fig. 3 Fuel Pump ModuleÐXJ ModelsÐInstallation
14 - 4 FUEL DELIVERY SYSTEMJ

FUEL PRESSURE RELEASE PROCEDURE
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT FUEL PRESSURE (EVEN WITH THE ENGINE
OFF) OF APPROXIMATELY 131-269 KPA (19-39 PSI).
THIS PRESSURE MUST BE RELEASED BEFORE
SERVICING ANY FUEL SUPPLY OR FUEL RETURN
SYSTEM COMPONENT.
(1) Disconnect negative battery cable.
(2) Remove fuel tank filler neck cap to release fuel
tank pressure.
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL WHEN THE
PRESSURE IS RELEASED FROM THE FUEL RAIL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN RELEASING FUEL SYSTEM PRESSURE.
(3) Remove protective cap from pressure test port
on the fuel rail (Fig. 7).
(4) Obtain the fuel pressure gauge/hose assembly
from fuel pressure gauge tool set 5069. Remove the
gauge from the hose.
(5) Place one end of hose (gauge end) into an ap-
proved gasoline container.
(6) Place a shop towel under the test port.
(7) To release fuel pressure, screw the other end of
hose onto the fuel pressure test port.
(8) After fuel pressure has been released, remove
the hose from the test port.
(9) Install protective cap to fuel test port.
FUEL SYSTEM PRESSURE TEST
The fuel system is equipped with a vacuum as-
sisted fuel pressure regulator (Fig. 8). With engine atidle speed, system fuel pressure should be approxi-
mately 214 kPa (31 psi) with the vacuum line con-
nected to the regulator. With the vacuum line
disconnected from the regulator, fuel pressure should
be approximately 269 kPa (39 psi). This is 55-69 kPa
(8-10 psi) higher.
(1) Remove the protective cap at the fuel rail (Fig.
7). Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from Gauge Set 5069) to test port pressure fit-
ting on fuel rail (Fig. 9).
(2) Note pressure gauge reading. Fuel pressure
should be approximately 214 kPa (31 psi) at idle.
(3) Disconnect vacuum line (hose) at fuel pressure
regulator (Fig. 8). Note gauge reading. With vacuum
line disconnected, fuel pressure should rise to ap-
proximately 269 kPa (39 psi).
Fuel pressure should be approximately 55-69 kPa
(8-10 psi) higher with vacuum line removed from reg-
ulator. If not, inspect pressure regulator vacuum line
for leaks, kinks or blockage. If vacuum line checks
Fig. 7 Pressure Test PortÐTypical
Fig. 8 Fuel Pressure RegulatorÐTypical
Fig. 9 Fuel Pressure Test ConnectionÐTypical
14 - 6 FUEL DELIVERY SYSTEMJ

OK and fuel pressure does not rise approximately
8-10 psi after disconnecting vacuum line, replace fuel
pressure regulator.
The fuel pressure regulator isnot adjustable.
(4) If fuel pressure exceeds 45 psi, check fuel re-
turn line/tube for kinks or obstructions.
If the previous tests checked good, fuel pump pres-
sure is correct. If pump pressure was low, proceed as
follows:
(5) Release fuel system pressure. Refer to the pre-
vious Fuel Pressure Release Procedure in this group.
(6) Disconnect the 5/16 inch fuel return line quick-
connect fitting at fuel rail. For procedures, refer to
Fuel Tubes/Lines/Hoses and Clamps. Also refer to
Quick-Connect Fittings. These can be found in the
Fuel Delivery System section of this group.
(7) Connect Fuel Line Pressure Test Adapter Tool
number 6539 (5/16 in.) between the disconnected fuel
return line and fuel rail (Fig. 10).
(8) Connect a 0-689 kPa (100 psi) pressure gauge
to Adapter Tool 6539.
WARNING: THE FUEL SYSTEM PRESSURE IN THE
FOLLOWING TEST MAY EXCEED 100 PSI. BEFORE
STARTING TEST, VERIFY GOOD CONNECTIONS AT
ENDS OF ADAPTER TOOL 6539. BE SURE TOOL IS
LOCKED ONTO FUEL RAIL AND FUEL RETURN
LINE. PULL FIRMLY ON ENDS OF TOOL TO VERIFY.
(9) To activate the fuel pump and pressurize the
system, obtain the DRB scan tool. Refer to the appro-
priate Powertrain Diagnostic Procedures service
manual for DRB operation.
(10)MOMENTARILYpinch the rubber hose por-
tion of adapter tool 6539. Pressure should rise to ap-
proximately 75 psi within two (2) seconds.DO NOT
pinch hose for longer than three seconds.
If fuel pump pressure rises to approximately 75 psi
within two seconds, pressure is operating at its max-
imum and is correct.If fuel pump pressure does not rise to approxi-
mately 75 psi within two seconds, proceed as follows:
(11) Release fuel system pressure. Refer to the pre-
vious Fuel Pressure Release Procedure in this group.
(12) Raise and support vehicle.
(13) Disconnect fuel supply line at inlet (fuel tank
side) of fuel filter. Connect Fuel Line Pressure Test
Adapter Tool number 6631 (3/8 in.) between fuel fil-
ter and fuel supply line.
WARNING: THE FUEL SYSTEM PRESSURE IN THE
FOLLOWING TEST MAY EXCEED 100 PSI. BEFORE
STARTING TEST, VERIFY GOOD CONNECTIONS AT
ENDS OF ADAPTER TOOL 6631. BE SURE TOOL IS
LOCKED ONTO FUEL FILTER AND FUEL SUPPLY
LINE. PULL FIRMLY ON ENDS OF TOOL TO VERIFY.
(14) To activate the fuel pump and pressurize the
system, obtain the DRB scan tool. Refer to the appro-
priate Powertrain Diagnostic Procedures service
manual for DRB operation.
MOMENTARILYpinch the rubber hose portion of
adapter tool 6631. Pressure should rise to approxi-
mately 75 psi within two (2) seconds.DO NOTpinch
hose for longer than three seconds.
If fuel pump pressure now rises to approximately
75 psi within two seconds, but this pressure could
not be met at the fuel rail, check for a plugged or re-
stricted fuel filter. Also check the fuel supply line be-
tween fuel filter and fuel rail for kinks or
obstructions. Proceed to the following Fuel Pump Ca-
pacity Test.
FUEL PUMP CAPACITY TEST
Before performing this test, verify fuel pump pres-
sure by performing the previous tests.
(1) Release the fuel system pressure from fuel sys-
tem. Refer to the previous Fuel Pressure Release
Procedure in this group.
(2) Disconnect the fuel supply line at fuel rail near
pressure regulator. For procedures, refer to Fuel
Tubes/Lines/Hoses and Clamps. Also refer to Quick-
Connect Fittings. These can be found in the Fuel De-
livery System section of this group.
(3) Connect Fuel Line Pressure Test Adapter Tool
number 6631 (3/8 in.) into the disconnected fuel sup-
ply line. Insert the other end of tool 6631 into an ap-
proved gasoline container.
(4) To activate the fuel pump and pressurize the
system, obtain the DRB scan tool. Refer to the appro-
priate Powertrain Diagnostic Procedures service
manual for DRB operation.
A good fuel pump will deliver at least 1 liter of fuel
per minute.
Fig. 10 Adapter ToolÐTypical Connection
JFUEL DELIVERY SYSTEM 14 - 7

FUEL PRESSURE LEAK DOWN TEST
ENGINE OFF
Abnormally long periods of cranking to restart a
hot engine that has been shut down for a short pe-
riod of time may be caused by:
²Fuel pressure bleeding past the fuel pressure reg-
ulator.
²Fuel pressure bleeding past the check valve in the
outlet end of the fuel tank mounted fuel pump.
²Fuel pressure bleeding past a fuel injector(s)
(1) Remove protective cap at fuel rail test port
(Fig. 11). With the engine off, connect the 0-414 kPa
(0-60 psi) fuel pressure gauge to the pressure test
port fitting on the fuel rail. The fitting on the pres-
sure tester must be in good condition and free of any
leaks before performing this test.
(2) Start the vehicle and let engine idle. Check fuel
pressure reading on gauge. Fuel pressure should be
within specifications. Refer to the previous Fuel Sys-
tem Pressure Tests.
(3) Shut engine off. Observe and record fuel pres-
sure reading on gauge. Leave fuel pressure gauge
connected. Allow engine to set for 30 minutes and
then compare the fuel pressure reading on the gauge
with the reading taken when engine was shut down.
A pressure drop of up to 138 kPa (20 psi) within 30
minutes is within specifications.
(4) If the fuel pressure drop is within specifica-
tions, the fuel pump outlet check valve and fuel pres-
sure regulator are both operating normally.
(5) If fuel pressure drop is greater than 138 kPa
(20 psi), it must be determined if this drop is being
caused by (in-tank mounted) fuel pump outlet check
valve or fuel pressure regulator. Proceed to next step.
(6) Release the fuel system pressure from fuel sys-
tem. Refer to the previous Fuel Pressure Release
Procedure in this group.(7) Disconnect both fuel lines at fuel rail near fuel
pressure regulator. For procedures, refer to Fuel
Tubes/Lines/Hoses and Clamps. Also refer to Quick-
Connect Fittings. These can be found in the Fuel De-
livery System section of this group.
(8) Connect Fuel Line Pressure Test Adapter Tool
number 6631 (3/8 in.) between the disconnected fuel
supply line and fuel rail (Fig. 12).
(9) Connect Fuel Line Pressure Test Adapter Tool
number 6539 (5/16 in.) between the disconnected fuel
return line and fuel rail (Fig. 12).
(10) Start engine. Observe and record fuel system
pressure.
(11) Shut engine off.
(12) Clamp off the rubber hose portion of adapter
tool number 6539 connected to the fuel return line.
Allow engine to set for 30 minutes. If pressure has
dropped more than 138 kPa (20 psi) in 30 minutes,
pressure is bleeding past the (in-tank mounted) fuel
pump outlet check valve. Replace Fuel Pump Module
assembly. Refer to Fuel Pump Module removal and
installation in this group. If pressure drop is within
specifications, proceed to next step.
(13) Clamp off the rubber hose portion of adapter
tool number 6631 connected to the fuel supply line.
Allow engine to set for 30 minutes. If pressure has
dropped more than 138 kPa (20 psi) in 30 minutes,
pressure is bleeding past the fuel pressure regulator.
Replace fuel pressure regulator. Refer to Fuel Rail re-
moval and installation in the Component Removal/
Installation section of this group.
MECHANICAL MALFUNCTIONS
Mechanical malfunctions are more difficult to diag-
nose with this system. The powertrain control mod-
ule (PCM) has been programmed to compensate for
some mechanical malfunctions such as incorrect cam
timing, vacuum leaks, etc. If engine performance
problems are encountered and diagnostic trouble
Fig. 11 Fuel Pressure Test PortÐTypical
Fig. 12 Adapter ToolsÐTypical Connections
14 - 8 FUEL DELIVERY SYSTEMJ

codes are not displayed, the problem may be mechan-
ical rather than electronic.
FUEL FILTER
The fuel filter protects the fuel injectors and fuel
pressure regulator from dirt, water and other foreign
matter. The filter is located under the vehicle along
the frame rail (Figs. 13 or 14). Replace fuel filter at
intervals specified in the Lubrication and Mainte-
nance Schedule chart found in Group 0, Lubrication
and Maintenance.
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT FUEL PRESSURE (EVEN WITH THE ENGINE
OFF) OF APPROXIMATELY 131-269 KPA (19-39 PSI).
THIS PRESSURE MUST BE RELEASED BEFORE
SERVICING THE FUEL FILTER.
(1) Disconnect negative battery cable. Remove fuel
filler cap.
WARNING: FUEL PRESSURE MUST BE RELEASED
BEFORE DISCONNECTING ANY FUEL SYSTEM
COMPONENT.
(2) Release fuel system pressure. Refer to Fuel
Pressure Release Procedure in this group.
(3) Raise and support vehicle.
(4) On YJ models remove the fuel filter shield (Fig.
13).
(5) Remove hoses and clamps from inlet and outlet
sides of filter (Figs. 13 or 14). For procedures, refer to
Fuel Tubes/Lines/Hoses and Clamps. Also refer to
Quick-Connect Fittings. These can be found in the
Fuel Delivery System section of this group.
(6) Remove retaining strap bolt.
(7) Remove filter from vehicle.
INSTALLATION
CAUTION: The ends of the fuel filter are marked for
correct installation. Install filter with the end marked
IN towards fuel tank and the end marked OUT to-
wards engine.
(1) Place fuel filter in retaining strap with the
marked ends in the correct position.
(2) Install retaining strap bolt and tighten to 12
Nzm (106 in. lbs.) torque.
(3) Install inlet and outlet hoses and hose clamps.
For procedures, refer to Fuel Tubes/Lines/Hoses and
Clamps. Also refer to Quick-Connect Fittings. These
can be found in the Fuel Delivery System section of
this group.
(4) On YJ models, install fuel filter shield (Fig. 13).
(5) Lower vehicle.
(6) Connect negative battery cable.
(7) Start engine and check for leaks.
FUEL TUBES/LINES/HOSES AND CLAMPS
Also refer to the proceeding section on Quick-Con-
nect Fittings.
Fig. 13 Fuel Filter and ShieldÐYJ Models
Fig. 14 Fuel FilterÐXJ Models
JFUEL DELIVERY SYSTEM 14 - 9