1995 JEEP YJ service

BUMPERS
INDEX
page page
Frame Crossmember Cover................. 16
Front Bumper............................ 16Rear Bumper............................ 16
Service Information........................ 16
SERVICE INFORMATION
In some cases, components in the following proce-
dures either support, or are hidden by other compo-
nents.
FRONT BUMPER
The YJ front bumper is a one-piece rail (Fig. 1). A
front crossmember cover (Fig. 1) is also installed on
all YJ vehicles.
BUMPER REMOVAL
(1) Disconnect and remove the fog lamps, if
equipped.
(2) Remove the nuts and bolts that retain the
bumper extensions to the bumper rail and remove
the extensions.
(3) Remove the nuts and bolts that attach the
bumper rail/tow hooks to the frame rails.
(4) Separate the bumper rail from the frame rails.
BUMPER INSTALLATION
(1) Position the front bumper on the frame rails.(2) Install the bolts and attach the front bumper
rail (and tow hooks, if equipped) to the frame rails.
(3) Tighten the bolts to 102 Nzm (75 ft. lbs.) torque.
(4) Position the bumper extensions on the bumper
rail and install the retaining bolts.
(5) Tighten the bolts to 104 Nzm (77 ft. lbs.) torque.
(6) Install the fog lamps, if equipped.
FRAME CROSSMEMBER COVER
REMOVAL
(1) Remove the screws that attach the crossmem-
ber cover and support to the frame rails.
(2) Remove the crossmember cover and support
from the frame rails.
INSTALLATION
(1) Position the support and crossmember cover on
the frame rails.
(2) Install the attaching screws.
(3) Tighten the screws to 8 Nzm (72 in. lbs.) torque.
REAR BUMPER
When equipped with a spare tire carrier attached
to the tailgate, a rear bumperette is attached to the
frame (Fig. 2 and 3).
Fig. 2 Rear Bumperette
Fig. 1 Front Bumper Rail, Crossmember Cover &
Tow Hooks
13 - 16 YJÐBUMPERSJ

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

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

WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
PRESSURE RELEASE PROCEDURE IN THIS
GROUP.
Inspect all hose connections such as clamps, cou-
plings and fittings to make sure they are secure and
leaks are not present. The component should be re-
placed immediately if there is any evidence of degra-
dation that could result in failure.
Never attempt to repair a plastic fuel line/tube. Re-
place as necessary.
Avoid contact of any fuel tubes/hoses with other ve-
hicle components that could cause abrasions or scuff-
ing. Be sure that the plastic fuel lines/tubes are
properly routed to prevent pinching and to avoid heat
sources.
The lines/tubes/hoses used on fuel injected vehicles
are of a special construction. This is due to the
higher fuel pressures and the possibility of contami-
nated fuel in this system. If it is necessary to replace
these lines/tubes/hoses, only those marked EFM/EFI
may be used.
The hose clamps used to secure rubber hoses on
fuel injected vehicles are of a special rolled edge con-
struction. This construction is used to prevent the
edge of the clamp from cutting into the hose. Only
these rolled edge type clamps may be used in this
system. All other types of clamps may cut into the
hoses and cause high-pressure fuel leaks.
Use new original equipment type hose clamps.
Tighten hose clamps to 1 Nzm (15 in. lbs.) torque.
QUICK-CONNECT FITTINGS
Also refer to the previous Fuel Tubes/Lines/Hoses
and Clamps section.
Different types of quick-connect fittings are used to
attach various fuel system components. These are: a
single-tab type, a two-tab type or a plastic retainer
ring type.
SINGLE-TAB TYPE
This type of fitting is equipped with a single pull
tab (Fig. 15). The tab is removable. After the tab is
removed, the quick-connect fitting can be separated
from the fuel system component.
CAUTION: The interior components (O-rings, spac-
ers) of this type of quick-connect fitting are not ser-
viced separately, but new pull tabs are available. Do
not attempt to repair damaged fittings or fuel lines/
tubes. If repair is necessary, replace the complete
fuel tube assembly.WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
PRESSURE RELEASE PROCEDURE IN THIS
GROUP.
DISCONNECTION/CONNECTION
(1) Disconnect negative battery cable from battery.
(2) Perform the fuel pressure release procedure.
Refer to the Fuel Pressure Release Procedure in this
section.
(3) Clean the fitting of any foreign material before
disassembly.
(4) Press the release tab on the side of fitting to re-
lease pull tab (Fig. 15).
CAUTION: If this release tab is not pressed prior to
releasing the pull tab, the pull tab will be damaged.
(5) While pressing the release tab on the side of
the fitting, use a screwdriver to pry up the pull tab
(Fig. 16).
(6) Raise the pull tab until it separates from the
quick-connect fitting (Fig. 17). Discard the old pull
tab.
(7) Disconnect the quick-connect fitting from the
fuel system component being serviced.
(8) Inspect the quick-connect fitting body and fuel
system component for damage. Replace as necessary.
(9) Prior to connecting the quick-connect fitting to
component being serviced, check condition of fitting
and component. Clean the parts with a lint-free
cloth. Lubricate them with clean engine oil.
(10) Insert the quick-connect fitting into the fuel
tube or fuel system component until the built-on stop
on the fuel tube or component rests against back of
fitting.
Fig. 15 Single-Tab Type Fitting
14 - 10 FUEL DELIVERY SYSTEMJ

(11) Obtain a new pull tab. Push the new tab down
until it locks into place in the quick-connect fitting.
(12) Verify a locked condition by firmly pulling on
fuel tube and fitting (15-30 lbs.).
(13) Connect negative cable to battery.
(14) Start engine and check for leaks.
TWO-TAB TYPE FITTING
This type of fitting is equipped with tabs located on
both sides of the fitting (Fig. 18). These tabs are sup-
plied for disconnecting the quick-connect fitting from
component being serviced.
CAUTION: The interior components (O-rings, spac-
ers) of this type of quick-connect fitting are not ser-
viced separately, but new plastic retainers are
available. Do not attempt to repair damaged fittings
or fuel lines/tubes. If repair is necessary, replace
the complete fuel tube assembly.
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
PRESSURE RELEASE PROCEDURE IN THIS
GROUP.
DISCONNECTION/CONNECTION
(1) Disconnect negative battery cable from the bat-
tery.
(2) Perform the fuel pressure release procedure.
Refer to the Fuel Pressure Release Procedure in this
section.
(3) Clean the fitting of any foreign material before
disassembly.
(4) To disconnect the quick-connect fitting, squeeze
the plastic retainer tabs against the sides of the
quick-connect fitting with your fingers. Tool use is
not required for removal and may damage plastic re-
tainer. Pull the fitting from the fuel system compo-
nent being serviced. The plastic retainer will remain
on the component being serviced after fitting is dis-
connected. The O-rings and spacer will remain in the
quick-connect fitting connector body.
(5) Inspect the quick-connect fitting body and com-
ponent for damage. Replace as necessary.
CAUTION: When the quick-connect fitting was dis-
connected, the plastic retainer will remain on the
component being serviced. If this retainer must be
removed, very carefully release the retainer from
the component with two small screwdrivers. After
removal, inspect the retainer for cracks or any dam-
age.
(6) Prior to connecting the quick-connect fitting to
component being serviced, check condition of fitting
and component. Clean the parts with a lint-free
cloth. Lubricate them with clean engine oil.
Fig. 16 Disconnecting Single-Tab Type Fitting
Fig. 17 Removing Pull Tab
Fig. 18 Typical Two-Tab Type Quick-Connect Fitting
JFUEL DELIVERY SYSTEM 14 - 11

(7) Insert the quick-connect fitting to the compo-
nent being serviced and into the plastic retainer.
When a connection is made, a click will be heard.
(8) Verify a locked condition by firmly pulling on
fuel tube and fitting (15-30 lbs.).
(9) Connect negative cable to battery.
(10) Start engine and check for leaks.
PLASTIC RETAINER RING TYPE FITTING
This type of fitting can be identified by the use of a
full-round plastic retainer ring (Fig. 19) usually black
in color.
CAUTION: The interior components (O-rings, spac-
ers, retainers) of this type of quick-connect fitting
are not serviced separately. Do not attempt to repair
damaged fittings or fuel lines/tubes. If repair is nec-
essary, replace the complete fuel tube assembly.WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
PRESSURE RELEASE PROCEDURE IN THIS
GROUP.
DISCONNECTION/CONNECTION
(1) Disconnect negative battery cable from the bat-
tery.
(2) Perform the fuel pressure release procedure.
Refer to the Fuel Pressure Release Procedure in this
section.
(3) Clean the fitting of any foreign material before
disassembly.
(4) To release the fuel system component from the
quick-connect fitting, firmly push the fitting towards
the component being serviced while firmly pushing
the plastic retainer ring into the fitting (Fig. 19).
With the plastic ring depressed, pull the fitting from
the component.The plastic retainer ring must be
pressed squarely into the fitting body. If this re-
tainer is cocked during removal, it may be dif-
ficult to disconnect fitting. Use an open-end
wrench on the shoulder of the plastic retainer
ring to aid in disconnection.
After disconnection, the plastic retainer ring will
remain with the quick-connect fitting connector body.
(5) Inspect fitting connector body, plastic retainer
ring and fuel system component for damage. Replace
as necessary.
(6) Prior to connecting the quick-connect fitting to
component being serviced, check condition of fitting
and component. Clean the parts with a lint-free
cloth. Lubricate them with clean engine oil.
(7) Insert the quick-connect fitting into the compo-
nent being serviced until a click is felt.
(8) Verify a locked condition by firmly pulling on
fuel tube and fitting (15-30 lbs.).
(9) Connect negative battery cable to battery.
(10) Start engine and check for leaks.
Fig. 19 Plastic Retainer Ring Type Fitting
14 - 12 FUEL DELIVERY SYSTEMJ

energized). This is done to compensate for the re-
duced flow through injector caused by the lowered
voltage.
BRAKE SWITCHÐPCM INPUT
When the brake light switch is activated, the pow-
ertrain control module (PCM) receives an input indi-
cating that the brakes are being applied. After
receiving this input, the PCM maintains idle speed to
a scheduled rpm through control of the idle air con-
trol (IAC) motor. The brake switch input is also used
to operate the speed control system.
CAMSHAFT POSITION SENSORÐPCM INPUT
A sync signal is provided by the camshaft position
sensor located in the distributor (Fig. 5). The sync
signal from this sensor works in conjunction with the
crankshaft position sensor to provide the powertrain
control module (PCM) with inputs. This is done to es-
tablish and maintain correct injector firing order.
Refer to Camshaft Position Sensor in Group 8D, Ig-
nition System for more information.
DATA LINK CONNECTORÐPCM INPUT
The data link connector (diagnostic scan tool con-
nector) links the DRB scan tool with the powertrain
control module (PCM). The data link connector is lo-
cated in the engine compartment (Figs. 6 or 7). For
operation of the DRB scan tool, refer to the appropri-
ate Powertrain Diagnostic Procedures service man-
ual.
The data link connector uses two different pins on
the PCM. One is for Data Link Transmit and the
other is for Data Link Receive.
INTAKE MANIFOLD AIR TEMPERATURE SENSORÐ
PCM INPUT
The intake manifold air temperature sensor is in-
stalled in the intake manifold with the sensor ele-
ment extending into the air stream (Figs. 8 or 9). Thesensor provides an input voltage to the powertrain
control module (PCM) indicating intake manifold air
temperature. The input is used along with inputs
from other sensors to determine injector pulse width.
As the temperature of the air-fuel stream in the
manifold varies, the sensor resistance changes. This
results in a different input voltage to the PCM.
CRANKSHAFT POSITION SENSORÐPCM INPUT
This sensor is a Hall Effect device that detects
notches in the flywheel (manual transmission), or
flexplate (automatic transmission).
This sensor is used to indicate to the powertrain
control module (PCM) that a spark and or fuel injec-
tion event is to be required. The output from this
sensor, in conjunction with the camshaft position sen-
sor signal, is used to differentiate between fuel injec-
tion and spark events. It is also used to synchronize
the fuel injectors with their respective cylinders.
Refer to Group 8D, Ignition System for more crank-
shaft position sensor information.
Fig. 5 Camshaft Position Sensor
Fig. 6 Data Link ConnectorÐYJ ModelsÐTypical
Fig. 7 Data Link ConnectorÐXJ ModelsÐTypical
14 - 22 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ

The throttle body has an air control passage that
provides air for the engine at idle (the throttle plate
is closed). The IAC motor pintle protrudes into the
air control passage and regulates air flow through it.
Based on various sensor inputs, the powertrain con-
trol module (PCM) adjusts engine idle speed by mov-
ing the IAC motor pintle in and out of the air control
passage. The IAC motor is positioned when the igni-
tion key is turned to the On position.
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 PCM.
IGNITION COILÐPCM OUTPUT
System voltage is supplied to the ignition coil pos-
itive terminal. The powertrain control module (PCM)
operates the ignition coil.Base (initial) ignition
timing is not adjustable.The PCM adjusts ignition
timing to meet changing engine operating conditions.
The ignition coil is located near the distributor
(Fig. 22).
Refer to Group 8D, Ignition System for additional
information.
MALFUNCTION INDICATOR LAMPÐPCM OUTPUT
The malfunction indicator lamp illuminates each
time the ignition key is turned on. It will stay on for
approximately three seconds as a bulb test. The lamp
is displayed on the instrument panel as the CHECK
ENGINE lamp (Figs. 23 or 24).
If the powertrain control module (PCM) receives an
incorrect signal, or no signal from certain sensors or
emission related systems, the lamp is turned on. This
is a warning that the PCM has recorded a system or
sensor malfunction. In some cases, when a problem is
declared, the PCM will go into a limp-in mode. This
is an attempt to keep the system operating. It signals
an immediate need for service.The lamp can also be used to display a Diagnostic
Trouble Code (DTC). Cycle the ignition switch On-
Off-On-Off-On within three seconds and any codes
stored in the PCM memory will be displayed. This is
done in a series of flashes representing digits. Refer
to On-Board Diagnostics in the General Diagnosis
section of this group for more information.
RADIATOR FAN RELAYÐPCM OUTPUT
XJ MODELS ONLY
The electric radiator cooling fan used in XJ models
(equipped with 4.0L engine, heavy duty cooling
and/or air conditioning) is controlled by the power-
train control module (PCM) through radiator fan re-
lay. The relay is energized when coolant temperature
is above 103ÉC (217ÉF). It will then de-energize when
Fig. 22 Ignition CoilÐTypical
Fig. 23 Check Engine LampÐXJ ModelsÐTypical
Fig. 24 Check Engine LampÐYJ ModelsÐTypical
14 - 28 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATIONJ