1994 JEEP CHEROKEE Service Repair Manual

SPECIFICATIONS
IGNITION OFF DRAW (IOD) DIAGNOSIS
GENERAL INFORMATION
Ignition off draw refers to power being drained
from the battery with the ignition switch turned off.
A normal vehicle electrical system will draw from 5
to 20 milliamps. This is with the ignition switch in
the OFF position, and all non-ignition controlled cir-
cuits in proper working order. A vehicle that has not
been operated for approximately 20 days, may dis-
charge the battery to an inadequate level. Battery
drain should not exceed approximately 20 MA (20
milliamps = 0.020 amps).
The 20 MA are needed to supply PCM memory,
digital clock memory, and ETR (electronically tuned
radio) memory.
Excessive battery drain is caused by items left
turned on, internally shorted generator, or intermit-
tent short in wiring.
If the IOD is over 20 milliamperes, the defect must
be found and corrected before replacing a battery. In
most cases the battery can be charged and returned
to service.
When a vehicle will not be used for 20 days or
more (stored), remove IOD fuse in the Power Distri-
bution Center to reduce battery discharging.
TEST PROCEDURE
Testing for higher amperage IOD must be per-
formed first to prevent damage to most milliamp
meters.
(1) Verify that all electrical accessories are OFF.
Turn off all lamps, remove ignition key, and close all
doors. If the vehicle is equipped with electronic acces-
sories (illuminated entry, high line radio), allow the
systems to automatically shut off (time out), up to 3
minutes.
(2) Determine that the underhood lamp is operat-
ing properly, then disconnect or remove bulb.
(3) Disconnect negative cable from battery.
(4) Connect a typical 12-volt test lamp (low watt-
age bulb) between the negative cable clamp and the
battery negative terminal. If equipped with security
alarm, cycle the key in the door to turn off the flash-ing lights. Make sure that the doors remain closed so
that illuminated entry is not activated.
The test lamp may light brightly for up to 3 min-
utes or may not light at all (depending on the elec-
trical equipment). The term brightly being used
throughout the following tests, implies the bright-
ness of the test lamp will be the same as if it were
connected across the battery.
The test lamp must be securely clamped to the neg-
ative cable and battery terminal. If the test lamp be-
comes disconnected during any part of the IOD test,
the electronic timer function will be activated and all
tests must be repeated.
If the ammeter circuit is broken the Security
Alarm Module will turn on parking lamps.
(5) After 3 minutes, the test lamp should turn OFF
or be DIMLY lit (depending on the electrical equip-
ment). If the test lamp remains brightly lit do not
disconnect it. Remove each fuse or circuit breaker
(refer to Group 8 - Wiring Diagrams) until test lamp
is either OFF or DIMLY lit. This will eliminate the
higher amperage draw.
If test lamp is still bright after disconnecting each
fuse and circuit breaker, disconnect the wiring har-
ness from the generator. Refer to Generator Test Pro-
cedures in this group. Do not disconnect the test
lamp.
After higher amperage IOD has been corrected, low
amperage IOD may be checked.
It is now safe to install milliamp meter to check for
low amperage IOD.
(6) With test lamp still connected securely, clamp
an ammeter between battery negative terminal and
negative battery cable.
Do not open any doors or turn on any electri-
cal accessories with the test lamp disconnected
or the meter may be damaged.
(7) Disconnect test lamp. The current draw should
not exceed 0.020 amp. If it exceeds 0.020 milliamps,
isolate each circuit by removing circuit breakers and
fuses. The meter reading drops once the high current
problem is found. Repair this section of the circuit,
whether it is a wiring short or component failure.
BATTERY CLASSIFICATIONS AND RATINGSTORQUE SPECIFICATIONS
8A - 8 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

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

(1) Connect positive lead of voltmeter to battery
negative post. Connect negative voltmeter lead to
battery negative cable clamp (Fig. 2). Rotate and
hold ignition switch in the START position. Observe
voltmeter. If voltage is detected, correct poor contact
between cable clamp and post.
(2) Connect positive lead of voltmeter to battery
positive post. Connect negative lead to battery cable
positive clamp (Fig. 2). Rotate and hold ignition
switch in the START position. Observe voltmeter. If
voltage is detected, correct poor contact between ca-
ble clamp and post.
(3) Connect a voltmeter to measure between the
battery positive post and the center of the B+ starter
solenoid stud (Fig. 3).
(4) Rotate and hold ignition switch in the START
position. If voltage reads above 0.2 volt, correct poor
STARTING SYSTEM DIAGNOSIS
TEST CONDITIONS
²PLACE GEAR SELECTOR IN PARK OR NEUTRAL AND SET PARK BRAKE OR EQUIVALENT.
²VERIFY BATTERY STATE-OF-CHARGE AND CRANKING CAPACITY, SEE BATTERY SECTION.
²CLEAN BATTERY TOP, POSTS, AND TERMINALS.
²VERIFY GENERATOR DRIVE BELT TENSION.
²DISCONNECT AND GROUND COIL CABLE.
Fig. 1 Volt-Amps Tester Connections (Typical)
8A - 10 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

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

(3) Check for continuity between solenoid terminal and
solenoid housing. There should be continuity (Fig. 7).
(4) If there is continuity, solenoid is good. If there
is no continuity in either test, solenoid has an open
circuit and is defective. Replace starter motor.
(5) Install starter as described in Group 8B.
(6) Connect field coil wire to field coil terminal.
STARTER RELAY OPERATION/TESTING
The starter relay is in the Power Distribution Cen-
ter (Figs. 8 and 9). Refer to the underside of the
Power Distribution Center cover for relay location.
OPERATION
²Terminal No. 30 is usually connected to battery
voltage and can be switched or B+ at all times.
²Terminal No. 87A is connected to terminal 30 in
the de-energized position.
²Terminal No. 87 is connected to terminal 30 in the
energized position which supplies battery voltage to
the operated device.
²Terminal No. 86 is connected to the electromagnet
and usually connected to a switched power source.²Terminal No. 85 is connected to the electromagnet
and is usually grounded by a switch or Powertrain
Control Module.
TESTING
Remove relay from Power Distribution Center to
perform the following tests.
²A relay in the de-energized position should have
continuity between terminal 87A and terminal 30.
²Resistance value between terminals 85 and 86
(electromagnet) is 7565 ohms.
²Connect a battery to terminals 85 and 86. There
should be continuity between terminal 30 and 87.
Fig. 9 Power Distribution CenterÐYJ
STARTER RELAY CONNECTIONS
Fig. 7 Continuity Test Between Solenoid Terminal
and Solenoid Case
Fig. 8 Power Distribution CenterÐXJ
8A - 12 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

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