Content .. 86 87 88 89 ..

Jeep Grand Cherokee WJ. Manual - part 88

SPECIFICATIONS

BATTERY SPECIFICATIONS

CRANKING RATING

The current battery can deliver for 30 seconds and

maintain a terminal voltage of 7.2 volts or greater at
specified temperature.

Fig. 14 Cleaning Battery Cable Terminal

1 – BATTERY CABLE CLEANING TOOL
2 – BATTERY CABLE

Reserve

Cold Cranking

Reserve

(Amps)

Rating @ -17.8C (0.0F)

Capacity

DIN/BCI

MIN.

300 Amp

300/600 Amp

120 Minutes

335 Amp

420/670 Amp

110 Minutes

8A - 10

BATTERY

SERVICE PROCEDURES (Continued)

2000 JEEP GRAND CHEROKEE

STARTING SYSTEMS

TABLE OF CONTENTS

page

DESCRIPTION AND OPERATION

STARTING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . 1
STARTER MOTOR. . . . . . . . . . . . . . . . . . . . . . . . . 2
STARTER RELAY . . . . . . . . . . . . . . . . . . . . . . . . . 2

DIAGNOSIS AND TESTING

STARTING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . 3
STARTER MOTOR. . . . . . . . . . . . . . . . . . . . . . . . . 7

STARTER RELAY . . . . . . . . . . . . . . . . . . . . . . . . . 8

REMOVAL AND INSTALLATION

STARTER MOTOR. . . . . . . . . . . . . . . . . . . . . . . . . 9
STARTER RELAY . . . . . . . . . . . . . . . . . . . . . . . . 11

SPECIFICATIONS

STARTING SYSTEM . . . . . . . . . . . . . . . . . . . . . . 12

DESCRIPTION AND OPERATION

STARTING SYSTEM

DESCRIPTION

An electrically operated engine starting system is

standard factory-installed equipment on this model.
The starting system is designed to provide the vehi-
cle operator with a convenient, efficient and reliable
means of cranking and starting the internal combus-
tion engine used to power the vehicle and all of its
accessory systems from within the safe and secure
confines of the passenger compartment. See the own-
er’s manual in the vehicle glove box for more infor-
mation and instructions on the recommended use
and operation of the factory-installed starting sys-
tem.

The starting system consists of the following com-

ponents:

• Battery

• Starter relay

• Starter motor (including an integral starter sole-

noid)

• Ignition switch

• Park/neutral position switch

• Wire harnesses and connections (including the

battery cables).

This group provides complete service information

for the starter motor and the starter relay. Complete
service information for the other starting system
components can be located as follows:

• Refer to Battery in the proper section of Group

8A - Battery for complete service information for the
battery.

• Refer to Ignition Switch and Key Lock Cyl-

inder in the proper section of Group 8D - Ignition
System for complete service information for the igni-
tion switch.

• Refer to Park/Neutral Position Switch in the

proper section of Group 21 - Transmission for com-
plete service information for the park/neutral posi-
tion switch.

• Refer to the proper section of Group 8W - Wir-

ing Diagrams for complete service information and
circuit diagrams for the starting system wiring com-
ponents.

Group 8A covers the Battery, Group 8B covers the

Starting Systems, and Group 8C covers the Charging
System. We have separated these systems to make it
easier to locate the information you are seeking
within this Service Manual. However, when attempt-
ing to diagnose any of these systems, it is important
that you keep their interdependency in mind.

The battery, starting, and charging systems in the

vehicle operate with one another, and must be tested
as a complete system. In order for the vehicle to start
and charge properly, all of the components that are
used in these systems must perform within specifica-
tions.

The diagnostic procedures used in each of these

groups include the most basic conventional diagnostic
methods, to the more sophisticated On-Board Diag-
nostics (OBD) built into the Powertrain Control Mod-
ule (PCM). Use of an induction-type milliampere
ammeter, volt/ohmmeter, battery charger, carbon pile
rheostat (load tester), and 12-volt test lamp may be
required.

All OBD-sensed systems are monitored by the

PCM. Each monitored circuit is assigned a Diagnos-
tic Trouble Code (DTC). The PCM will store a DTC in
electronic memory for any failure it detects. Refer to
On-Board Diagnostic Test For Charging System
in the Diagnosis and Testing section of Group 8C -
Charging System for more information.

STARTING SYSTEMS

8B - 1

OPERATION

The starting system components form two separate

circuits. A high-amperage feed circuit that feeds the
starter motor between 150 and 350 amperes, and a
low-amperage control circuit that operates on less
than 20 amperes. The high-amperage feed circuit
components include the battery, the battery cables,
the contact disc portion of the starter solenoid, and
the starter motor. The low-amperage control circuit
components include the ignition switch, the park/
neutral position switch, the starter relay, the electro-
magnetic windings of the starter solenoid, and the
connecting wire harness components.

Battery voltage is supplied through the low-amper-

age control circuit to the coil battery terminal of the
starter relay when the ignition switch is turned to
the momentary Start position. The park/neutral posi-
tion switch is installed in series between the starter
relay coil ground terminal and ground. This normally
open switch prevents the starter relay from being
energized and the starter motor from operating
unless the automatic transmission gear selector is in
the Neutral or Park positions.

When the starter relay coil is energized, the nor-

mally open relay contacts close. The relay contacts
connect the relay common feed terminal to the relay
normally open terminal. The closed relay contacts
energize the starter solenoid coil windings.

The energized solenoid pull-in coil pulls in the sole-

noid plunger. The solenoid plunger pulls the shift
lever in the starter motor. This engages the starter
overrunning clutch and pinion gear with the starter
ring gear on the automatic transmission torque con-
verter drive plate.

As the solenoid plunger reaches the end of its

travel, the solenoid contact disc completes the high-
amperage starter feed circuit and energizes the sole-
noid plunger hold-in coil. Current now flows between
the solenoid battery terminal and the starter motor,
energizing the starter.

Once the engine starts, the overrunning clutch pro-

tects the starter motor from damage by allowing the
starter pinion gear to spin faster than the pinion
shaft. When the driver releases the ignition switch to
the On position, the starter relay coil is de-energized.
This causes the relay contacts to open. When the
relay contacts open, the starter solenoid plunger
hold-in coil is de-energized.

When the solenoid plunger hold-in coil is de-ener-

gized, the solenoid plunger return spring returns the
plunger to its relaxed position. This causes the con-
tact disc to open the starter feed circuit, and the shift
lever to disengage the overrunning clutch and pinion
gear from the starter ring gear.

Following are general descriptions of the major

components in the starting system.

STARTER MOTOR

DESCRIPTION

The starter motors used for both the 4.0L and the

4.7L engines available in this model are very similar,
but are not interchangeable. Both starter motors are
mounted with two screws to the automatic transmis-
sion torque converter housing and are located on the
right side of the engine.

Each of these starter motors incorporates several

of the same features to create a reliable, efficient,
compact, lightweight and powerful unit. The electric
motors of both starters feature four electromagnetic
field coils wound around four pole shoes, and four
brushes contact the motor commutator. Both starter
motors are rated at 1.4 kilowatts (about 1.9 horse-
power) output at 12 volts.

Both of these starter motors are serviced only as a

unit with their starter solenoids, and cannot be
repaired. If either component is faulty or damaged,
the entire starter motor and starter solenoid unit
must be replaced.

OPERATION

These starter motors are equipped with a plane-

tary gear reduction (intermediate transmission) sys-
tem. The planetary gear reduction system consists of
a gear that is integral to the output end of the elec-
tric motor armature shaft that is in continual
engagement with a larger gear that is splined to the
input end of the starter pinion gear shaft. This fea-
ture makes it possible to reduce the dimensions of
the starter. At the same time, it allows higher arma-
ture rotational speed and delivers increased torque
through the starter pinion gear to the starter ring
gear.

The starter motors for both engines are activated

by an integral heavy duty starter solenoid switch
mounted to the overrunning clutch housing. This
electromechanical switch connects and disconnects
the feed of battery voltage to the starter motor and
actuates a shift fork that engages and disengages the
starter pinion gear with the starter ring gear.

Both starter motors use an overrunning clutch and

starter pinion gear unit to engage and drive a starter
ring gear that is integral to the torque converter
drive plate mounted on the rear crankshaft flange.

STARTER RELAY

DESCRIPTION

The starter relay is an electromechanical device

that switches battery current to the pull-in coil of the
starter solenoid when the ignition switch is turned to
the Start position. The starter relay is located in the
Power Distribution Center (PDC), in the engine com-

8B - 2

STARTING SYSTEMS

DESCRIPTION AND OPERATION (Continued)

partment. See the fuse and relay layout label affixed
to the inside surface of the PDC cover for starter
relay identification and location.

The starter relay is a International Standards

Organization (ISO) micro-relay. Relays conforming to
the ISO specifications have common physical dimen-
sions, current capacities, terminal patterns, and ter-
minal

functions.

The

ISO

micro-relay

terminal

functions are the same as a conventional ISO relay.
However, the ISO micro-relay terminal pattern (or
footprint) is different, the current capacity is lower,
and the physical dimensions are smaller than those
of the conventional ISO relay.

The starter relay cannot be repaired or adjusted

and, if faulty or damaged, it must be replaced.

OPERATION

The ISO relay consists of an electromagnetic coil, a

resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.

When the electromagnetic coil is de-energized,

spring pressure returns the movable contact to the
normally closed position. The resistor or diode is con-
nected in parallel with the electromagnetic coil in the
relay, and helps to dissipate voltage spikes that are
produced when the coil is de-energized.

DIAGNOSIS AND TESTING

STARTING SYSTEM

DIAGNOSIS

The battery, starting, and charging systems oper-

ate with one another, and must be tested as a com-
plete system. In order for the vehicle to start and
charge properly, all of the components involved in
these systems must perform within specifications.

Group 8A covers the Battery, Group 8B covers the

The diagnostic procedures used in these groups

include the most basic conventional diagnostic meth-
ods, to the more sophisticated On-Board Diagnostics
(OBD) built into the Powertrain Control Module
(PCM). Use of an induction-type milliampere amme-
ter, volt/ohmmeter, battery charger, carbon pile rheo-
stat (load tester), and 12-volt test lamp may be
required.

All OBD-sensed systems are monitored by the

STARTING SYSTEMS

8B - 3

DESCRIPTION AND OPERATION (Continued)

Content .. 86 87 88 89 ..