ECO mode JEEP CHEROKEE 1994 Service Owner's Guide

With the ignition key in the ON position and en-
gine not running, check the sensor output voltage at
the center terminal wire of the connector. Check this
at idle (throttle plate closed) and at wide open throt-
tle (WOT). At idle, sensor output voltage should be
greater than 200 millivolts. At wide open throttle,
sensor output voltage must be less than 4.8 volts.
The output voltage should increase gradually as the
throttle plate is slowly opened from idle to WOT.
OXYGEN SENSOR TESTS
For diagnosis, removal or installation, refer to
Group 14, Fuel Systems in this manual.
ON-BOARD DIAGNOSTICS (OBD)
FOR IGNITION SYSTEM COMPONENTS
The powertrain control module (PCM) has been
programmed to monitor certain ignition system cir-
cuits:
EXAMPLE:
If a reference signal is not being detected during
engine cranking from the crankshaft position sensor,
a Diagnostic Trouble Code (DTC) number 11 can be
observed at the Check Engine Lamp.
If the problem is sensed in a monitored circuit of-
ten enough to indicate an actual problem, a DTC is
stored. The DTC will be stored in the PCM memory
for eventual display to the service technician. If the
problem is repaired or ceases to exist, the PCM can-
cels the DTC after 51 engine starts.
Certain criteria must be met for a DTC to be en-
tered into PCM memory. The criteria may be a spe-
cific range of engine rpm, engine temperature and/or
input voltage to the PCM.
A DTC indicates that the PCM has recognized an
abnormal signal in a circuit or the system. A DTC
may indicate the result of a failure, but never iden-
tify the failed component directly.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal-
function has occurred. Refer to On-Board Diagnostics
(OBD) in Group 14, Fuel Systems for additional in-
formation.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble Code (DTC) can be dis-
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the Malfunction
Indicator Lamp. This lamp was formerly referred to
as the Check Engine Lamp. The lamp is located on
the instrument panel.
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB
connects to the data link connector in the enginecompartment (Figs. 32 or 33). For operation of the
DRB, refer to the appropriate Powertrain Diagnostic
Procedures service manual.
EXAMPLES:
²If the lamp flashes 1 time, pauses and flashes 1
more time, a flashing Diagnostic Trouble Code (DTC)
number 11 is indicated.
²If the lamp flashes 3 times, pauses and flashes 5
more times, a flashing Diagnostic Trouble Code
(DTC) number 35 is indicated.
After any stored DTC information has been ob-
served, the display will end with a flashing DTC
number 55. This will indicate the end of all stored
information.
ERASING TROUBLE CODES
After the problem has been repaired, the DRB scan
tool must be used to erase a DTC. Refer to the ap-
propriate Powertrain Diagnostic Procedures service
manual for operation of the DRB scan tool.
Fig. 32 Data Link ConnectorÐYJ ModelsÐTypical
Fig. 33 Data Link ConnectorÐXJ ModelsÐTypical
JIGNITION SYSTEMS 8D - 19

COMPONENT REMOVAL/INSTALLATION
INDEX
page page
Automatic Shut Down (ASD) Relay........... 20
Camshaft Position Sensor.................. 20
Crankshaft Position Sensor................. 21
Distributor.............................. 23
Engine Coolant Temperature Sensor.......... 22
General Information....................... 20
Ignition Coil............................. 26Intake Manifold Air Temperature Sensor....... 27
Manifold Absolute Pressure (MAP) Sensor..... 27
Oxygen (O2S) Sensor..................... 28
Powertrain Control Module (PCM)............ 28
Spark Plug Secondary Cables............... 29
Spark Plugs............................ 28
Throttle Position Sensor (TPS).............. 29
GENERAL INFORMATION
This section of the group, Component Removal/In-
stallation, will discuss the removal and installation
of ignition system components.
For basic ignition system diagnostics and service
adjustments, refer to the Diagnostics/Service Proce-
dures section of this group.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
AUTOMATIC SHUT DOWN (ASD) RELAY
The ASD relay is installed in the Power Distribu-
tion Center (PDC) (Fig. 1). Relay location is printed
on the PDC cover.
REMOVAL
(1) Remove the PDC cover.
(2) Remove the relay by lifting straight up.
INSTALLATION
(1) Check the condition of relay wire terminals at
PDC before installing relay. Repair as necessary.
(2) Push the relay into the connector.
(3) Install the relay cover.
CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the dis-
tributor.
REMOVAL
(1) Remove the distributor. Refer to Distributor
Removal.
(2) Remove the distributor rotor.
CAUTION: Do not position the distributor in a vise
when removing or installing the drive gear roll pin.
Support the distributor with wooden blocks.
(3) Mark the position of the gear and the shaft in
line with the roll pin. The gearMUSTbe installed
back to its original position on the distributor shaft.
(4) Using a small pin punch and hammer, remove
the distributor gear roll (spring) pin (Fig. 3).
(5) Lightly tap the end of the distributor shaft un-
til distributor gear and thrust washer are removed.
(6) Slide the distributor shaft out of the distributor
housing.
(7) Remove the camshaft position sensor mounting
screw and positioning arm (Fig. 4).
(8) Slide the wire harness grommet out of the dis-
tributor housing. Remove the camshaft position sen-
sor.
Fig. 1 PDCÐXJ Models
Fig. 2 PDCÐYJ Models
8D - 20 IGNITION SYSTEMSJ

other side. When coolant temperature is too high the
switch closes providing a path to ground, and the indi-
cator bulb lights.
TACHOMETER
The tachometer displays the engine speed (RPM).
With the engine running, the tachometer receives an
engine speed signal from the Powertrain Control
Module pin 43 (values shown in Specifications chart).
SPEEDOMETER/ODOMETER SYSTEM
The speedometer/odometer system consists of an elec-
tric speedometer and pushbutton reset odometer
mounted in the cluster. The system also includes the
wire harness from the cluster to the vehicle speed sen-
sor at the transmission, and the adapter and pinion in
the transmission. A signal is sent from a transmission
mounted vehicle speed sensor to the speedometer/odom-
eter circuitry through the wiring harness. Refer to
Group 21 - Transmission for selecting the proper pinion,
and selecting and indexing the proper adapter.
FUEL GAUGE
The fuel gauge pointer position is controlled by a
magnetic field created by electrical current flow through
the coils within the gauge. A change in current flow will
change the magnetic field which changes the pointer po-
sition. The fuel level sender is a variable resistor that
changes electrical resistance with a change of the level
of fuel in the tank (values shown in Specifications
chart).
LOW FUEL WARNING LAMP
The low fuel warning lamp will light when the fuel
level falls below approximately 4 gallons. A low fuel
warning module controls when the lamp will light.
When the module senses 66.5 ohms or less from the
fuel level sender for 10 continuous seconds, the lamp
will light. The lamp will remain on until the module
senses 63.5 ohms or more from the fuel level sender
for 20 continuous seconds.
UPSHIFT INDICATOR LAMP
Vehicles equipped with manual transmissions have an
optional upshift indicator lamp. The lamp is controlled
by the Powertrain Control Module. The lamp lights to
indicate when the driver should shift to the next high-
est gear for best fuel economy. The Powertrain Control
Module will turn the lamp off after 3 to 5 seconds if the
upshift is not performed. The lamp will remain off until
the vehicle stops accelerating and is brought back to the
range of lamp operation or shifted into another gear.
The indicator lamp is normally illuminated when
the ignition switch is turned ON and is turned off
when the engine is started. The lamp will be lighted
during engine operation according to engine speed
and load.
BRAKE INDICATOR LAMP
The brake indicator lamp warns the driver that the
parking brake is applied or that hydraulic pressure in
the split brake system is unequal.
Voltage is supplied through the brake indicator
bulb to 3 switches. A path to ground for the current
is available if:
²The brake warning switch is closed (with unequal
brake system hydraulic pressures), or
²
The ignition switch is in the START position (to test
the bulb), or
²The park brake switch is closed (with the parking
brake applied).
ANTI-LOCK BRAKE SYSTEM (ABS) INDICATOR
LAMP
The anti-lock brake system (ABS) lamp lights to in-
dicate a system self-check is in process at vehicle
start-up. If light remains on after start-up or comes
on and stays on while driving, it may indicate that
the ABS system has detected a malfunction or has
become inoperative.
4WD INDICATOR LAMP
COMMAND-TRAC 4WD
The PART TIME lamp lights when the vehicle is en-
gaged in four-wheel drive mode. Voltage is supplied to
one side of the indicator bulb. A switch in the transfer
case area is connected to the other side of the indicator
bulb. When the switch is closed, a path to ground is pro-
vided and the indicator bulb lights.
SELECT-TRAC 4WD
The four-wheel drive icon or FULL TIME lamp
lights when the vehicle is engaged in full time four-
wheel drive mode. The PART TIME lamp lights when
the vehicle is in part time four-wheel drive mode.
Voltage is supplied to one side of the indicators.
Switches in the transfer case area are connected to
the other side of the indicator bulbs. When a switch
is closed, a path to ground is provided and the indi-
cator bulb lights.
MALFUNCTION INDICATOR LAMP (CHECK ENGINE)
The Malfunction Indicator Lamp (Check Engine)
lights each time the ignition switch is turned ON and
stays on for 3 seconds as a bulb test.
If the PCM receives an incorrect signal or no signal
from certain sensors or emission related systems the
lamp is turned on (pin 32 of PCM). This is a warning
that the PCM has recorded a system or sensor mal-
function. In some cases when a diagnostic trouble
code is declared the PCM will go into a limp-in mode
in an attempt to keep the system operating. It sig-
nals an immediate need for service.
The lamp also can be used to display diagnostic
trouble codes (DTC). Cycle the ignition switch ON,
OFF, ON, OFF, ON within 5 seconds. This will allow
any trouble codes stored in the PCM memory to be
displayed in a series of flashes representing digits.
8E - 2 XJ INSTRUMENT PANEL AND GAUGESJ

DIAGNOSINGÐALL LAMPS OUT
(1) Inspect fuse #9. Replace as required.
(2) Measure voltage at instrument cluster connec-
tor terminal 20. Meter should read zero ohms. If not,
repair open to ground.
UPSHIFT INDICATOR LAMP
Vehicles equipped with manual transmissions have
an optional upshift indicator lamp. The lamp is con-
trolled by the PCM. The lamp lights to indicate when
the driver should shift to the next highest gear for best
fuel economy. The PCM will turn the lamp off after 3 to
5 seconds if the upshift is not performed. The lamp will
remain off until the vehicle stops accelerating and is
brought back to the range of lamp operation or shifted
into another gear.
The indicator lamp is normally illuminated when
the ignition switch is turned ON and it is turned off
when the engine is started. The lamp will be lighted
during engine operation according to engine speed
and load.
(1) Turn ignition switch to ON.
(2) Ground pin 2 of cluster connector. Lamp should
light. If not, replace bulb. If OK, continue with step 3.
(3) Turn ignition switch to OFF. Check for conti-
nuity between cluster connector pin 2 and pin 54 of
the PCM. If not, repair open. If OK, refer to DRB
scan tool actuator test of upshift indicator.
BRAKE INDICATOR LAMP
The brake indicator is a dual function lamp. It will in-
dicate an unequal pressure condition in the split brake
hydraulic system and it also will indicate when the park-
ing brake is engaged. Separate switches are used for each
indicator lamp function. A switch mounted on the brake
pedal assembly will close a ground circuit whenever the
parking brakes are applied. A second switch is installed
in the brake hydraulic lines near the master cylinder. If
the switch is balanced by equal pressure on both ends of
the switch valve, the valve remains centered and the
lamp remains off. If the valve is shifted by unequal pres-
sure between the front or rear brake hydraulic systems,
the lamp circuit is connected to ground. To make sure
the brake lamp is functional before the vehicle is driven,
it is illuminated through a ground circuit when the igni-
tion switch is turned to the START position.
(1) Turn ignition switch to ON.
(2) Ground pin 1 of the cluster connector. Lamp
should light. If not, replace bulb. If OK, continue
with step 3.
(3) Turn ignition switch to OFF. Check for continuity to
park brake switch and brake warning switch.
MALFUNCTION INDICATOR LAMP (CHECK ENGINE)
The Malfunction Indicator Lamp (Check Engine) il-
luminates each time the ignition switch is turned
ON and stays on for 3 seconds as a bulb test.If the PCM receives an incorrect signal or no signal
from certain sensors or emission related systems the
lamp is turned on (pin 32 of PCM). This is a warning
that the PCM has recorded a system or sensor mal-
function. In some cases when a diagnostic fault is de-
clared the PCM will go into a limp-in mode in an
attempt to keep the system operating. It signals an
immediate need for service.
The lamp also can be used to display diagnostic
trouble codes (DTC). Cycle the ignition switch ON,
OFF, ON, OFF, ON within 5 seconds. This will allow
any DTC's stored in the PCM memory to be dis-
played in a series of flashes representing digits.
(1) Turn ignition switch to ON.
(2) Ground pin 4 of cluster connector. Lamp should
light. If not, replace bulb. If OK, continue with step 3.
(3) Turn ignition switch to OFF. Check for conti-
nuity between cluster connector pin 4 and PCM cav-
ity 32. If OK, replace PCM. If not, repair open.
SEAT BELT REMINDER LAMP
Apply 12 volts to terminal 16 of cluster connector.
Lamp should light. If not, replace bulb. If OK, check
wiring for an open to buzzer module. Refer to Group
8U - Chime/Buzzer Warning Systems.
INSTRUMENT PANEL ILLUMINATION LAMPS
The instrument panel illumination lamps share
two common connections. There is a splice after fuse
#10 that connects the lamps to battery feed. There is
also a splice that connects all lamps to ground. Be-
cause they share these common connection points in
a parallel circuit, the illumination lamps will all
come on at the same time. It also means one or more
lamps can be out without affecting the operation of
the other lamps.
On the battery side of the circuit, the headlamp
switch illumination rheostat/switch and panel lamps
fuse receive battery feed in series from the park/tail
fuse. In the park lamp position, the headlamp switch
completes the circuit from the park/tail fuse to the il-
lumination rheostat/switch and panel lamps fuse.
The illumination rheostat contains a variable resis-
tor that allows the driver to vary illumination inten-
sity from off to full brightness.
DIAGNOSIS
(1) Turn parking lamps ON.
(2) Check fuse #10. Replace as required.
(3) Measure voltage at battery side of fuse #10
with rheostat turned counterclockwise to clockwise
(LO to HI). Meter should read zero volts to battery
voltage. If not, replace headlamp switch.
(4) Measure resistance at ground side of fuse #10
with parking lamps OFF. Meter should read almost
zero ohms (except bulb filament). If not, repair open
to ground. If zero ohms, 12 volt supply wire from fuse
is shorted to ground, repair short.
8E - 16 YJ INSTRUMENT PANEL AND GAUGESJ

HORNS
CONTENTS
page page
GENERAL INFORMATION.................. 1
HORN SWITCH (HORN PAD) REPLACEMENT . . 3
TORQUE SPECIFICATIONS................. 3XJ ..................................... 1
YJ ..................................... 2
GENERAL INFORMATION
For XJ/YJ vehicles battery voltage is applied to the
horn relay through a fuse.
When the horn switch is depressed, the horn relay
is grounded, pulling the contact closed and providing
battery voltage to the horns.
A slip ring and brush arrangement in the steering
wheel allows the switch circuit to maintain contact
while allowing rotation of the steering wheel.On XJ models, a cadmium-plated ground
screw is used to attach the horn(s) to the body.
Do not substitute other types of ground screws
as they may become corroded and cause a loss
of ground.
XJ
REPLACEMENT
(1) Raise and support the vehicle.
(2) Remove the splash shield.
(3) Remove horn mounting bolt and horn mounted
on the drivers side (Fig. 1).
(4) Remove wire from horn.
(5) To install horn, reverse the removal proce-
dures.
DIAGNOSIS AND REPAIR
Refer to Group 8W - Wiring Diagrams for a com-
plete circuit diagram.
HORN RELAY
²Inspect 25 amp, #11 fuse. Replace fuse as re-
quired.
²Depress horn switch. The relay contacts should
click. If OK, go to HORNS. If not, go to next step.
²Remove the horn relay located in the relay center.
The relay center is on the lower instrument panel
trim cover just right of the steering column (Fig. 2).
There should be 12 volts at relay connector pins 1
and 2. If not, repair open in circuit to relay.
²Depress horn switch. Measure resistance between
relay connector pin 5 and ground. The meter should
read zero ohms. If not, repair open to horn switch
ground.
²Measure resistance between relay connector pin 4
and ground. The meter should read almost zero ohms
(horn resistance) If OK, replace relay. If not, repair
open in circuit between relay and horns.
Fig. 1 Drivers Side Horn
JHORNS 8G - 1

²Measure voltage at wiper/washer switch connector
terminal B. Meter should read battery voltage. If
OK, repair open to washer pump. If not, replace
switch.
DIAGNOSING WINDSHIELD WASHER
(INTERMITTENT)
(1) Unplug washer pump connector.
²Measure resistance between terminal B at pump
and a clean chassis ground. Meter should read zero
ohms. If not, repair open to ground.
(2) Turn ignition switch to ACCESSORY and
washer switch to ON.
²Measure voltage at wipe module switch connector
terminal B (pink wire). Meter should read battery
voltage. If not, replace wiper switch.
²Measure voltage at wipe module motor connector
terminal B (brown wire). Meter should read battery
voltage. If not, replace module.
²Measure voltage at washer pump connector termi-
nal A at pump. Meter should read battery voltage. If
OK, replace pump. If not, repair open from wipe
module.
INTERMITTENT WIPER MODULE
The intermittent wiper module is non-serviceable.
Refer to the wiring schematic for connector call outs.
The intermittent wiper module is attached to the
lower instrument panel cover near the steering col-
umn with a patch of velcro.
LIFTGATE WIPER
GENERAL
The rear wiper motor contains electronic controls
to provide three operating modes.
²Intermittent wipe witha5to8second delay be-
tween sweeps.
²Constant wipe that operates in conjunction with a
washer.
²Park mode that operates when ignition or rear
wiper switch is turned OFF.
The rear wiper switch is located in the instrument
panel and is supplied current when the ignition
switch is in the ON position. When the switch is
placed in the intermittent wipe position it provides
current to the rear wiper motor. When it is held in
the wash/wipe position it provides current to both the
motor and the rear washer pump. The switch is
spring loaded in the wash/wipe position.
REMOVAL
(1) Remove the wiper arm assembly from the pivot
pin by depressing the tab (Fig. 1) and pulling
straight out.
(2) Slide clip along hose until clip is off hose
mounting.
(3) Disconnect the washer hose.(4) Remove pivot pin retaining nut.
(5) Remove external bezel and seal.
(6) Remove the liftgate interior trim panel.
(7) Disconnect the wiper motor at the wiring harness.
(8) Remove the wiper motor mounting screws.
(9) Remove the wiper motor.
INSTALLATION
(1) Position the motor (Fig. 2) in the liftgate cavity
with the pivot pin protruding through the hole in the
liftgate.
Fig. 1 Rear Wiper Arm Removal
Fig. 2 Rear Wiper Motor Removal/Installation
JWINDSHIELD WIPERS 8K - 5

WIRE CODE IDENTIFICATION
Each wire shown in the diagrams contains a code
(Fig. 3) which identifies the main circuit, part of the
main circuit, gauge of wire, and color. The color is
shown as a two letter code which can be identified by
referring to the Wire Color Code Chart (Fig. 4). If the
wire has a tracer and it is a standard color an aster-
isk will follow the main wire color. If the tracer is
non-standard the main wire color will have a slash (/)
after it followed by the tracer color.
CIRCUIT IDENTIFICATION
All circuits in the diagrams use an alpha/numeric
code to identify the wire and its function. To identify
which circuit code applies to a system, refer to the
Circuit Identification Code Chart. This chart shows
the main circuits only and does not show the second-
ary codes that may apply to some models.
LOCATING A SYSTEM
To locate a system or component in the diagrams,
refer to the alphabetical index at the front of the di-
agrams. Determine the diagram sheet number. Sheet
numbers are located at the lower right or left handcorner of each sheet.Page numbers at the top of
the page do not apply to diagram sheets.
The index identifies the main system and all com-
ponents that relate to that system. There are also
sections of the index that identify specific compo-
nents only (for example modules, lamps, etc.). Refer
to a components name in the index if you are unclear
as to what a system may be called.
Diagram sheets are arranged starting with the bat-
tery and fuses. Then working into charging, starting,
and ignition systems. After this they start at the
front of the vehicle and work to rear. The diagrams
end with connector identification pages.
COMPONENT IDENTIFICATION
When looking for a components location in the vehicle
refer to the Component Identification section index.
This section shows the wire harness routing and the
components location in the vehicle. When using this sec-
tion refer to the wiring diagrams for the general loca-
tion of the component. Then use the component
identification index to locate the proper figure number.
SPLICE LOCATIONS
Splice locations are indicated in the diagrams by a
diamond with a splice circuit code within it (Fig. 5
example 1). If there is more than one splice per cir-
cuit a small box will be connected to it with the
splice number in it (Fig. 5 example 2).
To locate a splice in the wiring harness determine
the splice number from the wiring diagrams then re-
fer to the splice location index. This section shows
the general location of the splice in the harness.
Fig. 2 Secondary Ignition Wiring 4.0L
Fig. 3 Wire Color Code Identification
Fig. 4 Wire Color Code Chart
8W - 2 WIRING DIAGRAMSJ

FUEL SYSTEM
CONTENTS
page page
ACCELERATOR PEDAL AND THROTTLE CABLE... 16
FUEL DELIVERY SYSTEM................. 2
FUEL TANKS........................... 12
GENERAL INFORMATION.................. 1
MULTI-PORT FUEL INJECTION (MFI)ÐCOMPO-
NENT DESCRIPTION/SYSTEM OPERATION . 17MULTI-PORT FUEL INJECTION (MFI)Ð
COMPONENT REMOVAL/INSTALLATION . . . 54
MULTI-PORT FUEL INJECTION (MFI)Ð
GENERAL DIAGNOSIS.................. 32
SPECIFICATIONS....................... 62
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation or
by the particular vehicle nameplate. A chart showing
a breakdown of the alphabetical designations is in-
cluded 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 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 be
covered 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. Gener-
ally, premium unleaded gasolines contain more addi-
tive than regular unleaded gasolines.
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

line. You may encounter fuels containing 3 percent
or more methanol along with other alcohols called co-
solvents.
Problems that are the result of using methanol/gas-
oline blends are not the responsibility of Chrysler
Corporation. They may not be covered by the vehicle
warranty.
MTBE/ETBE
Gasoline and MTBE (Methyl Tertiary Butyl Ether)
blends are a mixture of unleaded gasoline and up to
15 percent MTBE. Gasoline and ETBE (Ethyl Ter-
tiary Butyl Ether) are blends of gasoline and up to
17 percent ETBE. Gasoline blended with MTBE or
ETBE may be used in your vehicle.CLEAN AIR GASOLINE
Many gasolines are now being blended that con-
tribute to cleaner air, especially in those areas of the
country where air pollution levels are high. These
new blends provide a cleaner burning fuel and some
are referred to asReformulated Gasoline.
In areas of the country where carbon monoxide lev-
els are high, gasolines are being treated with oxy-
genated materials such as MTBE, ETBE and
ethanol.
Chrysler Corporation supports these efforts toward
cleaner air and recommends that you use these gas-
olines as they become available.
FUEL DELIVERY SYSTEM
INDEX
page page
Fuel Filter............................... 8
Fuel Pressure Leak Down Test............... 7
Fuel Pressure Release Procedure............. 5
Fuel Pump Capacity Test................... 7
Fuel Pump Electrical Control................. 5Fuel Pump Module........................ 2
Fuel System Pressure Test.................. 5
Fuel Tubes/Lines/Hoses and Clamps........... 9
Quick-Connect Fittings..................... 9
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 gear/rotor
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 pumpis not operating, system fuel pressure of 131-269 kPa
(19-39 psi) is maintained. This is done by the fuel
pump outlet check valve and the vacuum assisted
fuel pressure regulator.
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.
14 - 2 FUEL SYSTEMJ

AIR CONDITIONING (A/C) CLUTCH RELAYÐPCM
OUTPUT
The powertrain control module (PCM) activates the
A/C compressor through the A/C clutch relay. The
PCM regulates A/C compressor operation by switch-
ing the ground circuit for the A/C clutch relay on
and off. The relay is located in the Power Distribu-
tion Center (PDC) (Figs. 17 or 18). For the location of
the relay within the PDC, refer to label on PDC
cover.
When the PCM receives a request for A/C from A/C
evaporator switch, it will adjust idle air control (IAC)
motor position. This is done to increase idle speed.
The PCM will then activate the A/C clutch through
the A/C clutch relay. The PCM adjusts idle air con-
trol (IAC) stepper motor position to compensate for
increased engine load from the A/C compressor.
By switching the ground path for the relay on and
off, the PCM is able to cycle the A/C compressor
clutch. This is based on changes in engine operating
conditions. If, during A/C operation, the PCM senses
low idle speeds or a wide open throttle condition, itwill de-energize the relay. This prevents A/C clutch
engagement. The relay will remain de-energized un-
til the idle speed increases or the wide open throttle
condition exceeds 15 seconds or no longer exists. The
PCM will also de-energize the relay if coolant tem-
perature exceeds 125ÉC (257ÉF).
AUTO SHUT DOWN (ASD) RELAYÐPCM OUTPUT
The ASD relay is located in the Power Distribution
Center (PDC) (Figs. 17 or 18). For the location of this
relay within the PDC, refer to label on PDC cover.
The ASD supplies battery voltage to the fuel pump,
fuel injector, ignition coil, generator field winding
and oxygen (O2S) sensor heating element. The
ground circuit for the coil in the ASD relay is con-
trolled by the powertrain control module (PCM). The
PCM operates the relay by switching the ground cir-
cuit on and off.
The fuel pump relay is controlled by the PCM
through same circuit that the ASD relay is con-
trolled.
The powertrain control module (PCM) energizes
the fuel pump through the fuel pump relay. (The
PCM was formerly referred to as the SBEC or engine
controller). Battery voltage is applied to the relay
from the ignition switch. The relay is energized when
a ground is provided by the PCM. The relay is lo-
cated in the Power Distribution Center (PDC) (Figs.
17 or 18). For the location of fuel pump relay within
PDC, refer to label on PDC cover.
For the 1994 model year, the ballast resistor and
ballast resistor bypass relay are no longer used to
control the fuel pump circuit.
DATA LINK CONNECTORÐPCM OUTPUT
Refer to the previous paragraphs on Data Link
ConnectorÐPCM Input for information.
EMR LAMPÐPCM OUTPUT
The EMR lamp is not used for the 1994 model
year.
Fig. 16 Vehicle Speed SensorÐTypical
Fig. 17 PDCÐYJ Models
Fig. 18 PDCÐXJ Models
14 - 24 FUEL SYSTEMJ