engine JEEP CHEROKEE 1994 Service Repair Manual

ENGINE BLOCK HEATER
GENERAL INFORMATION
DESCRIPTION AND OPERATION
An optional engine block heater is available for all
models. The heater is equipped with a power cord.
The cord is attached to an engine compartment com-
ponent with tie-straps. The heater warms the engine
providing easier engine starting and faster warm-up
in low temperatures. The heater is mounted in a core
hole of the engine cylinder block (in place of a freeze
plug) with the heating element immersed in engine
coolant. Connect the power cord to a grounded 110-
120 volt AC electrical outlet with a grounded, three-
wire extension cord.
WARNING: DO NOT OPERATE ENGINE UNLESS
BLOCK HEATER CORD HAS BEEN DISCONNECTED
FROM POWER SOURCE AND SECURED IN PLACE.
BLOCK HEATER SPECIFICATIONS
²2.5L Engine: 115 Volts 400 Watts
²4.0L Engine: 120 Volts 600 Watts
REMOVAL
Refer to correct illustration (Figures 11, 12 or 13)
when servicing block heater.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND PRES-
SURIZED. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
(1) Drain coolant from radiator and engine cylin-
der block.
(2) Unplug power cord from block heater.
(3) Loosen screw in center of block heater (Figs.
11, 12 or 13).
(4) Remove block heater from cylinder block.
INSTALLATION
(1) Thoroughly clean the engine core hole and the
block heater seat.
(2) Insert block heater assembly into core hole
with element loop pointingUp.
(3) Seat block heater flush against block face.
Tighten mounting screw to 3.6 Nzm (32 in. lbs.)
torque.
(4) Fill cooling system with coolant. Pressurize sys-
tem and inspect for leaks.
(5) Plug power cord into block heater. Route cord
away from moving parts, linkages and exhaust sys-
tem components. Secure cord in place with tie-straps.
Fig. 11 Heater and CordÐXJ with 2.5L Engine
Fig. 12 Heater and CordÐXJ with 4.0L Engine
Fig. 13 Heater and CordÐYJ Models
JCOOLING SYSTEM 7 - 37

SPECIFICATIONS
GENERAL INFORMATION
The following specifications are published from the
latest information available at the time of publica-
tion.If anything differs between the specifica-
tions found on the Vehicle Emission Control
Information (VECI) label and the following
specifications, use specifications on VECI label.
The VECI label is located in the engine compart-
ment.
DRIVE BELT TENSION
Belt tension can be adjusted only on models
equipped with conventional left hand drive. Refer to
the following Belt TensionÐExcept RHD Models
chart for specifications.
It is not necessary to adjust belt tension on right
hand drive (RHD) vehicles if equipped with a 4.0L
engine. The engine is equipped with an automatic
belt tensioner. The tensioner maintains correct belt
tension at all times.Due to the use of this belt
tensioner, DO NOT attempt to use a belt ten-
sion gauge on this engine.Refer to Automatic Belt
Tensioner for additional information.
COOLING SYSTEM CAPACITIES
BELT TENSIONÐEXCEPT RHD MODELS
7 - 38 COOLING SYSTEMJ

ELECTRICAL
GROUP INDEX
Group Group
AUDIO SYSTEMS....................... 8F
BATTERY/STARTER/GENERATOR SERVICE . . 8B
BATTERY/STARTING/CHARGING SYSTEMS
DIAGNOSTICS........................ 8A
CHIME/WARNING BUZZER SYSTEM....... 8U
HORNS............................... 8G
IGNITION SYSTEMS.................... 8D
INSTRUMENT PANEL AND GAUGES........ 8E
LAMPS............................... 8L
OVERHEAD CONSOLE................... 8CPOWER LOCKS........................ 8P
POWER MIRRORS...................... 8T
POWER SEAT.......................... 8R
POWER WINDOWS..................... 8S
REAR WINDOW DEFOGGER.............. 8N
TURN SIGNALS AND HAZARD WARNING
FLASHERS........................... 8J
VEHICLE SPEED CONTROL SYSTEM....... 8H
WINDSHIELD WIPERS AND WASHERS..... 8K
WIRING DIAGRAMS.................... 8W
BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
CONTENTS
page page
BATTERY TEST PROCEDURES............. 2
ENGINE STARTER MOTOR TEST
PROCEDURES ON VEHICLE.............. 9GENERATOR TEST PROCEDURES ON
VEHICLE............................. 14
IGNITION OFF DRAW (IOD) DIAGNOSIS...... 8
USING ON-BOARD DIAGNOSTIC SYSTEM.... 19
GENERAL INFORMATION
The battery, starting, and charging systems oper-
ate with one another, and therefore, must be thor-
oughly tested as a complete system. In order for the
vehicle to start and charge properly, it must have a
battery that will perform to specifications. The
starter motor, generator, wiring, and electronics also
must perform within specifications. Group 8A covers
starting (Fig. 1) and charging (Fig. 2) system diag-
nostic procedures. These procedures include the most
basic conventional methods to On-Board Diagnostics
(OBD) built into the Powertrain Control Module
(PCM). Use of an ammeter, volt/ohmmeter, battery
charger, carbon pile rheostat (load tester), and 12-
volt test lamp will be required.
All OBD sensing systems are monitored by the
PCM. The PCM will store in memory any detectable
failure in the monitored circuits. Refer to Using On-
Board Diagnostic System in this group for more in-
formation.
Fig. 1 Starting System Components (Typical)
JELECTRICAL 8A - 1

ENGINE STARTER MOTOR TEST PROCEDURES ON VEHICLE
INDEX
page page
2.5L Starter Motor Noise Diagnosis........... 13
General Information........................ 9
Starter Control Circuit Tests................ 11
Starter Feed Circuit Tests - (Voltage Drop Method).9
Starter System Diagnostic Inspections.......... 9
Starting System Cold Cranking Test........... 9
GENERAL INFORMATION
The starting system consists of an:
²ignition switch
²starter relay
²park/neutral position switch (automatic transmis-
sion)
²wiring harness
²battery
²starter motor with an integral solenoid.
These components form 2 separate circuits. A high
amperage circuit that feeds the starter motor up to
300+ amps, and a control circuit that operates on
less than 20 amps.
STARTER SYSTEM DIAGNOSTIC INSPECTIONS
Before removing any unit from the starter motor
system for repair, perform the following inspections:
BATTERY INSPECTION
To determine condition of the battery, perform the
testing procedure outlined in Battery Test Proce-
dures.
WIRING INSPECTION
Inspect wiring for damage. Inspect all connections
at the starter motor solenoid, park/neutral position
switch (if equipped), back-up lamp switch connector,
ignition switch, starter relay, and battery (including
all ground connections). Clean and tighten all con-
nections as required.
SOLENOID, RELAY AND IGNITION SWITCH
INSPECTION
Inspect the solenoid, relay and switch to determine
their condition. Also, if equipped with automatic
transmission, inspect condition of the park/neutral
position switch. Testing information can be found in
the following pages.
STARTING SYSTEM COLD CRANKING TEST
(1) Battery must first pass load and voltage drop
tests and be fully charged before proceeding. Refer to
Battery Test Procedures.(2) Connect a suitable volt-ampere tester to the
battery terminals (Fig. 1). Refer to the operating in-
structions provided with the tester being used.
(3) Fully engage parking brake, place manual
transmission in NEUTRAL, automatic transmission
in PARK.
(4) Verify that all lamps and accessories are OFF.
(5) Remove coil secondary cable from distributor
and connect to ground.
(6) Rotate and hold the ignition switch in the
START position. Note cranking voltage and amper-
age.
(a) If voltage reads above 9.6 volts and amperage
draw reads above specifications, go to Starter Feed
Circuit Tests.
(b) If voltage reads 12.5 volts or greater and am-
perage reads below specifications, go to Starter
Control Circuit Tests.
A cold engine will increase starter motor cur-
rent and reduce battery voltage.
STARTER FEED CIRCUIT TESTS - (VOLTAGE DROP
METHOD)
The voltage drop tests will determine if there is ex-
cessive resistance in the high current circuit. When
performing these tests, it is important that the volt-
meter be connected to the terminals that the cables
are connected to, instead of to the cables themselves.
For example, when testing between the battery and
solenoid, touch the voltmeter test probes to the bat-
tery post and the solenoid threaded stud. The follow-
ing operation will require a voltmeter, accurate to
1/10 of a volt.
Before performing the tests, assure the following
procedures are accomplished:
²remove coil secondary cable from distributor and
connect to ground
²transmission in NEUTRAL (manual transmission)
or PARK (automatic transmission)
²parking brake applied
²battery is fully charged (refer to Battery Test Pro-
cedures).
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 9

contact at battery cable to solenoid connection. If
reading is still above 0.2 volt, replace positive bat-
tery cable.
(5) Connect voltmeter to measure between the bat-
tery negative post and the engine block (Fig. 4).
(6) Rotate and hold ignition switch in the START po-
sition. If voltage reads above 0.2 volt, correct poor con-tact at ground cable attaching point. Voltage reading
still above 0.2 volt, replace ground cable.
(7) Connect positive voltmeter lead to starter mo-
tor housing. Connect negative lead to battery nega-
tive terminal (Fig. 5).
(8) Rotate and hold ignition switch in the START
position. If voltage reads above 0.2 volt, correct poor
starter to engine ground.
If resistance tests detect no feed circuit failures, re-
move the starter motor and go to Solenoid Testing.
STARTER CONTROL CIRCUIT TESTS
The starter control circuit consists of a starter so-
lenoid, starter relay, ignition switch, park/neutral po-
sition switch (automatic transmission), and all their
wiring and connections.
Testing procedures for these components are as fol-
lows and should be followed in order as described.
CAUTION: Before performing any test, disconnect dis-
tributor connector to prevent engine from starting.
SOLENOID TESTING
Refer to Group 8B - Battery/Starter/Generator Ser-
vice for starter removal procedures.
(1) Disconnect field coil wire from field coil terminal.
(2) Check for continuity between solenoid terminal
and field coil terminal with a continuity tester.
There should be continuity (Fig. 6).
Fig. 2 Test Battery Connection Resistance
Fig. 3 Test Positive Battery Cable Resistance
(Typical)
Fig. 4 Test Ground Circuit Resistance
Fig. 5 Test Starter Motor Ground (Typical)
Fig. 6 Continuity Test Between Solenoid Terminal
and Field Coil Terminal
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 11

IGNITION SWITCH TEST
After testing starter solenoid and relay and they
check out OK, trouble is probably with ignition
switch or its wiring.
Check all wiring for opens and shorts, and connec-
tions for being loose or corroded.
PARK/NEUTRAL POSITION SWITCH
Refer to Group 21 - Transmissions for diagnostic
information.
2.5L STARTER MOTOR NOISE DIAGNOSIS
If the complaint is similar to Conditions No. 1 and
No. 2 of chart below, correction can be achieved by
proper ``shimming'' according to the following proce-
dures:
²Disconnect the battery negative cable (to prevent
inadvertent starting of engine).Two shim thicknesses are available. One is
0.381 mm (0.015 in.) and the other is 1.143 mm
(0.045 in.).
If the complaint is similar to Condition No. 1, the
starter motor must be moved toward the flywheel/
driveplate using thinner shims (Fig. 10).
This is generally a condition that causes bro-
ken flywheel/driveplate ring gear teeth or bro-
ken starter motor housings.
If the complaint is similar to Condition No. 2, the
starter motor must be moved away from the fly-
wheel/driveplate. This is done by installing shim(s)
across both mounting pads. More than one shim may
be required.
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 13

GENERATOR TEST PROCEDURES ON VEHICLE
INDEX
page page
Diagnostic Procedures..................... 15
General Information....................... 14Operational Check with Battery Indicator
(Base Cluster Only)..................... 14
Operational Check with Voltmeter............ 15
GENERAL INFORMATION
The generator is belt-driven by the engine. All en-
gines use serpentine drive.
The amount of DC current produced by the gener-
ator is controlled by the Powertrain Control Module
(PCM) (Fig. 1).
All vehicles are equipped with On-Board Diagnos-
tics (OBD). All OBD sensing systems are monitored
by the PCM. The PCM will store in electronic mem-
ory any detectable failure within the monitored cir-
cuits. Refer to Using On-Board Diagnostic System in
this group for more information.
OPERATIONAL CHECK WITH BATTERY INDICATOR
(BASE CLUSTER ONLY)
When operating normally, the indicator bulb will
come on when the ignition switch is turned to the
ON or START position. After the engine starts, the
indicator bulb goes off. With the engine running, the
charge indicator should come on only when there is a
problem in the charging system (base cluster only).
Fig. 10 Starter Motor Shimming
Fig. 1 Charging System Components (Typical)
8A - 14 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

OPERATIONAL CHECK WITH VOLTMETER
When the ignition switch is turned to the ON po-
sition, battery potential will register on the voltme-
ter. During engine cranking a lower voltage will
appear on the meter. With the engine running, a
voltage reading higher than the first reading (igni-
tion in ON) should register.
DIAGNOSTIC PROCEDURES
If the indicator operates abnormally, or if an un-
dercharged or overcharged battery condition occurs,
the following procedures may be used to diagnose the
charging system.
Remember that an undercharged battery is often
caused by:
²accessories being left on overnight
²or by a defective switch which allows a bulb, such
as a liftgate or glove box light, to stay on (refer to
Ignition Off Draw Diagnosis).
VISUAL INSPECTION
²Inspect condition of battery cable terminals, bat-
tery posts, connections at engine block, starter motor
solenoid and relay. They should be clean and tight.
Repair as required.
²Inspect all fuses in the fuse block for tightness in
receptacles. They should be properly installed and
tight. Repair or replace as required.²Inspect the electrolyte level in the battery and add
water if necessary.
²Inspect generator mounting bolts for tightness. Re-
place or torque bolt as required. Refer to Torque
Specifications in Battery/Starter/Generator Service.
²Inspect generator drive belt condition and tension.
Tension or replace belt as required. Refer to Belt
Tension Specifications in Battery/Starter/Generator
Service.
²Inspect connection at generator B+ output. It
should be clean and tight. Repair as required.
GENERATOR OUTPUT WIRE RESISTANCE
TEST
Generator output wire resistance test will show
amount of voltage drop across generator output wire
between generator battery terminal and battery pos-
itive post.
PREPARATION
(1) Before starting test make sure vehicle has a
fully charged battery. Test and procedures on how to
check for a fully charged battery are shown in Bat-
tery Test Procedures.
(2) Turn OFF ignition switch.
(3) Disconnect negative cable from battery.
(4) Disconnect generator output wire from genera-
tor output battery terminal.
Fig. 2 Generator Output Wire Resistance Test (Typical)
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 15

(5) Connect a 0-150 ampere scale D.C. ammeter in
series between generator battery terminal and dis-
connected generator output wire (Fig. 2). Connect
positive lead to generator battery terminal and neg-
ative lead to disconnected generator output wire.
(6) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to disconnected generator out-
put wire. Connect negative lead of test voltmeter to
battery positive cable at positive post.
(7) Connect one end of a jumper wire to ground
and with other end probe green K20 lead wire at
back of generator (Fig. 2). This will generate a DTC.
CAUTION: Do not connect green/orange A142 lead
of wiring to ground. Refer to Group 8W - Wiring Di-
agrams for more information.
(8) Connect an engine tachometer and connect neg-
ative cable to battery.
(9) Connect a variable carbon pile rheostat be-
tween battery terminals. Be sure carbon pile is in
OPEN or OFF position before connecting leads. See
Load Testing in Battery Test Procedures for instruc-
tions.
TEST
(1) Start engine. Immediately after starting, re-
duce engine speed to idle.
(2) Adjust engine speed and carbon pile to main-
tain 20 amperes flowing in circuit. Observe voltmeter
reading. Voltmeter reading should not exceed 0.5
volts.
RESULTS
If a higher voltage drop is indicated, inspect, clean
and tighten all connections between generator bat-
tery terminal and battery positive post. A voltage
drop test may be performed at each connection to lo-
cate connection with excessive resistance. If resis-
tance tested satisfactorily, reduce engine speed, turn
OFF carbon pile and turn OFF ignition switch.
(1) Disconnect negative cable from battery.
(2) Remove test ammeter, voltmeter, carbon pile,
and tachometer.
(3) Remove jumper wire.
(4) Connect generator output wire to generator
battery terminal. Tighten to 5 to 6 NIm (45 to 75 in.
lbs.).
(5) Connect negative cable to battery.
(6) Use DRB scan tool to erase DTC.
GENERATOR OUTPUT TEST
Generator output test determines whether genera-
tor can deliver its rated current output.PREPARATION
(1) Before starting any tests make sure vehicle has
a fully charged battery. Test and procedures on how
to check for a fully charged battery are shown in
Battery Test Procedures.
(2) Disconnect negative cable from battery.
(3) Disconnect generator output wire at the gener-
ator battery terminal.
(4) Connect a 0-150 ampere scale D.C. ammeter in
series between generator battery terminal and dis-
connected generator output wire (Fig. 3). Connect
positive lead to generator battery terminal and neg-
ative lead to disconnected generator output wire.
(5) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to generator battery terminal.
(6) Connect negative lead of test voltmeter to a
good ground.
(7) Connect an engine tachometer and connect bat-
tery negative cable.
(8) Connect a variable carbon pile rheostat be-
tween battery terminals. Be sure carbon pile is in
OPEN or OFF position before connecting leads. See
Load Testing in Battery Test Procedures.
(9) Connect one end of a jumper wire to ground
and with other end probe green K20 lead wire at
back of generator (Fig. 3). This will generate a DTC.
CAUTION: Do not connect green/orange A142 lead
of wiring to ground. Refer to Group 8W - Wiring Di-
agrams for more information.
TEST
(1) Start engine. Immediately after starting reduce
engine speed to idle.
(2) Adjust carbon pile and engine speed in incre-
ments until a speed of 1250 rpm and voltmeter read-
ing of 15 volts is obtained.
CAUTION: Do not allow voltage meter to read above
16 volts.
(3) The ammeter reading must be within limits
shown for that size of generator being tested. See
Generator Specifications in Battery/Starter/Genera-
tor Service.
RESULTS
(1) If reading is less than specified and generator
output wire resistance is not excessive, generator
should be replaced. Refer to Group 8B - Battery/
Starter/Generator Service.
(2) After current output test is completed reduce
engine speed, turn OFF carbon pile and turn OFF ig-
nition switch.
(3) Disconnect negative cable from battery.
(4) Remove test ammeter, voltmeter, tachometer
and carbon pile.
8A - 16 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

USING ON-BOARD DIAGNOSTIC SYSTEM
OPERATION OF ON-BOARD DIAGNOSTIC
(OBD) SYSTEM
The Powertrain Control Module (PCM) monitors
critical input and output circuits of the charging sys-
tem making sure they are OK. Some are checked
continuously and some are checked only under cer-
tain conditions.
If OBD system senses that one critical circuit is
bad during the monitoring cycle, it will put a diag-
nostic trouble code into memory. Each input and out-
put circuit monitored by the OBD system has its own
diagnostic trouble code. The diagnostic trouble code
(DTC) will stay in memory as long as the circuit con-
tinues to be bad. If the problem does not happen
again after the fault code is put into memory, the
PCM is programmed to clear the memory after 50 en-
gine starts.
DIAGNOSTIC TROUBLE CODES (DTC)
Diagnostic trouble codes are two-digit numbers
flashed on Malfunction Indicator (Check Engine)
Lamp that identify which circuit is bad. In most
cases they do not identify which component in a cir-
cuit is bad. A trouble code description can be read us-
ing the DRB scan tool. Refer to Group 14 - Fuel
Systems for more information. Therefore, a DTC is
only a symptom, not necessarily the cause for the
problem. In some cases, because of the design of the
driveability test procedure, a DTC can be the reason
for the problem. It is important that the test proce-
dure be followed to understand what caused the DTC
of the on-board diagnostic system to be set.
HOW TO USE MALFUNCTION INDICATOR (CHECK
ENGINE) LAMP FOR DIAGNOSTIC TROUBLE
CODES
To start this function, cycle the ignition switch ON-
OFF-ON-OFF-ON within 5 seconds and any trouble
code stored in the PCM will be displayed. The Mal-
function Indicator (Check Engine) Lamp will display
a DTC by flashing on and off. There is a short pause
between flashes and a longer pause between digits.
All codes displayed are two digit numbers with a 4
second pause between codes.
An example of a code is as follows:
(1) Lamp on for 2 seconds, then turns off.
(2) Lamp flashes 4 times pauses and then flashes 1
time.
(3) Lamp pauses for 4 seconds, flashes 4 times,
pauses and then flashes 7 times.
The 2 codes are 41 and 47. Any number of codes
can be displayed as long as they are in memory. The
lamp will flash until all are displayed (55 = End of
test).
CHARGING SYSTEM DIAGNOSTIC TROUBLE
CODES
See Generator Diagnostic Trouble Code chart for
diagnostic trouble codes which apply to the charging
system. Refer to the Powertrain Diagnostic Proce-
dures manal to diagnose an On-Board Diagnostic
System, Trouble Code.
GENERATOR DIAGNOSTIC TROUBLE CODE (DTC)
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 19