Jeep XJ. Manual - part 87

DIAGNOSIS AND TESTING

STARTING SYSTEM

DIAGNOSIS

The battery, starting system and charging system

in the vehicle operate with one another, and must be
tested as a complete system. In order for the engine
to start and the battery to charge properly, all of the
components that are used in these systems must per-
form within specifications. The service information
for these systems has been separated within this ser-
vice manual to make it easier to locate the specific
information

you

are

seeking.

However,

when

attempting to diagnose any of these systems, it is
important that you keep their interdependency in
mind.

The diagnostic procedures used for the battery,

starting system and charging system include the
most basic conventional diagnostic methods, to the
more sophisticated On-Board Diagnostics (OBD) built
into the Powertrain Control Module (PCM). Use of an
induction-type milliampere ammeter, a volt/ohmme-
ter, a battery charger, a carbon pile rheostat (load
tester) and a 12-volt test lamp may be required. All
OBD-sensed systems are monitored by the PCM.
Each monitored circuit is assigned a Diagnostic Trou-
ble Code (DTC). The PCM will store a DTC in elec-
tronic memory for any failure it detects. Refer to
Charging System, On-Board Diagnostic Test in
the index of this service manual for the location of
the proper on-board diagnostic test procedures.

Starting System Diagnosis

Condition

Possible Cause

Correction

Starter fails to operate.

1. Battery discharged or
faulty.
2. Starting circuit wiring
faulty.
3. Starter relay faulty.
4. Ignition switch faulty.
5. Clutch pedal position
switch faulty.
6. Park/Neutral position
switch faulty or
misadjusted.
7. Starter solenoid faulty.
8. Starter motor faulty.

1. Refer to Battery in the index of this service manual for
the location of the proper battery diagnosis and testing
procedures. Replace the faulty battery, as required.
2. Refer to Starting System in the index of this service
manual for the location of complete starting system wiring
diagrams. Test and repair the faulty starter feed and/or
control circuits, as required.
3. Refer to Starter Relay in the index of this service
manual for the location ofr the proper starter relay
diagnosis and testing procedures. Replace the faulty
starter relay, as required.
4. Refer to Ignition Switch and Key Lock Cylinder in the
index of this service manual for the location of the proper
ignition switch diagnosis and testing procedures. Replace
the faulty ignition switch, as required.
5. Refer to Clutch Pedal Position Switch in the index of
this service manual for the location of the proper clutch
pedal position switch diagnosis and testing procedures.
Replace the faulty clutch hydraulic linkage unit, as
required.
6. Refer to Park/Neutral Position Switch in the index of
this service manual for the location of the proper
park/neutral position switch diagnosis and testing
procedures. Replace the faulty park/neutral position
switch, as required.
7. Refer to Starter Motor in the index of this service
manual for the location of the proper starter solenoid
diagnosis and testing procedures. Replace the faulty
starter motor, as required.
8. Refer to Starter Motor in the index of this service
manual for the location of the proper starter motor
diagnosis and testing procedures. Replace the faulty
starter motor, as required.

8B - 4

STARTING SYSTEMS

Starting System Diagnosis

Condition

Possible Cause

Correction

Starter engages, fails to
turn engine.

1. Battery discharged or
faulty.
2. Starting circuit wiring
faulty.
3. Starter motor faulty.
4. Engine seized.

Starter engages, spins
out before engine starts.

1. Starter ring gear faulty.
2. Starter motor faulty.

1. Refer to Starter Motor in the index of this service
manual for the location of the proper starter motor
removal and installation procedures. Remove the starter
motor to inspect the starter ring gear. Replace the faulty
starter ring gear, as required.
2. Refer to Starter Motor in the index of this service
manual for the location of the proper starter motor
diagnosis and testing procedures. Replace the faulty
starter motor, as required.

Starter does not
disengage.

1. Starter motor
improperly installed.
2. Starter relay faulty.
3. Ignition switch faulty.
4. Starter motor faulty.

1. Refer to Starter Motor in the index of this service
manual for the location of the proper starter motor
installation procedures. Tighten the starter motor
mounting hardware to the correct tightness specifications,
as required.
2. Refer to Starter Relay in the index of this service
manual for the location of the proper starter relay
diagnosis and testing procedures. Replace the faulty
starter relay, as required.
3. Refer to Ignition Switch and Key Lock Cylinder in the
index of this service manual for the location of the proper
ignition switch diagnosis and testing procedures. Replace
the faulty ignition switch, as required.
4. Refer to Starter Motor in the index of this service
manual for the location of the proper starter motor
diagnosis and testing procedures. Replace the faulty
starter motor, as required.

TESTING

Before testing the starting system perform a visual

inspection of the starting system components and
connections. Refer to Starting System in the index
of this service manual for the location of the proper
starting system cleaning and inspection procedures.

COLD CRANKING TEST

Refer to Starting System in the index of this ser-

vice manual for the location of complete starting sys-

tem wiring diagrams. Before performing this test, be
certain that the following procedures are accom-
plished:

• The battery is fully-charged and load tested.

Refer to Battery Charging in the index of this ser-
vice manual for the location of the proper battery
charging procedures. Refer to Battery in the index of
this service manual for the location of the battery
diagnosis

and

testing

procedures,

including

the

proper battery load test procedures.

STARTING SYSTEMS

8B - 5

DIAGNOSIS AND TESTING (Continued)

• Fully engage the parking brake.

• If the vehicle is equipped with an automatic

transmission, place the gearshift selector lever in the
Park position. If the vehicle is equipped with a man-
ual transmission, place the gearshift selector lever in
the Neutral position and block the clutch pedal in the
fully depressed position.

• Verify that all lamps and accessories are turned

off.

• To prevent the engine from starting, remove the

Automatic ShutDown (ASD) relay. The ASD relay is
located in the Power Distribution Center (PDC), in
the engine compartment. See the fuse and relay lay-
out label affixed to the underside of the PDC cover
for ASD relay identification and location.

(1) Connect a suitable volt-ampere tester to the

battery terminals (Fig. 3). See the instructions pro-
vided by the manufacturer of the volt-ampere tester
being used.

(2) Rotate and hold the ignition switch in the Start

position. Note the cranking voltage and current
(amperage) draw readings shown on the volt-ampere
tester.

(a) If the voltage reads below 9.6 volts, refer to

Starter Motor in the index of this service manual
for the location of the proper starter motor diagno-
sis and testing procedures. If the starter motor
tests OK, refer to Engine Diagnosis in the index
of this service manual for the location of the proper
engine diagnosis and testing procedures. If the
starter motor is not OK, replace the faulty starter
motor.

(b) If the voltage reads above 9.6 volts and the

current (amperage) draw reads below specifica-
tions, refer to the Feed Circuit Test in this sec-
tion.

the starter motor does not turn, refer to the Con-
trol Circuit Test in this section.

(d) If the voltage reads 12.5 volts or greater and

the starter motor turns very slowly, refer to the
Feed Circuit Test in this section.

NOTE: A cold engine will increase the starter cur-
rent (amperage) draw reading, and reduce the bat-
tery voltage reading.

FEED CIRCUIT TEST

The starter feed circuit test (voltage drop method)

will determine if there is excessive resistance in the
high-amperage starter feed circuit. Refer to Starting
System in the index of this service manual for the
location of complete starting system wiring diagrams.

When performing the voltage drop test, it is impor-

tant to remember that the voltage drop is giving an
indication of the resistance between the two points at
which the voltmeter probes are attached. EXAM-
PLE: When testing the resistance of the battery pos-
itive cable, touch the voltmeter leads to the battery
positive cable terminal clamp and to the battery pos-
itive cable eyelet terminal at the starter solenoid
B(+) terminal stud. If you probe the battery positive
terminal post and the battery positive cable eyelet
terminal at the starter solenoid B(+) terminal stud,
you are reading the combined voltage drop in the
battery positive cable terminal clamp-to-terminal
post connection and the battery positive cable.

The following operation will require a voltmeter

accurate to 1/10 (0.10) volt. Before performing this
test, be certain that the following procedures are
accomplished:

• The battery is fully-charged and load tested.

and

testing

procedures,

including

the

proper battery load test procedures.

• Fully engage the parking brake.

• If the vehicle is equipped with an automatic

• Verify that all lamps and accessories are turned

off.

Fig. 3 Volts-Amps Tester Connections - Typical

1 – POSITIVE CLAMP
2 – NEGATIVE CLAMP
3 – INDUCTION AMMETER CLAMP

8B - 6

STARTING SYSTEMS

DIAGNOSIS AND TESTING (Continued)

• To prevent the engine from starting, remove the

(1) Connect the positive lead of the voltmeter to

the battery negative terminal post. Connect the neg-
ative lead of the voltmeter to the battery negative
cable terminal clamp (Fig. 4). Rotate and hold the
ignition switch in the Start position. Observe the
voltmeter. If voltage is detected, correct the poor con-
tact between the battery negative cable terminal
clamp and the battery negative terminal post.

(2) Connect the positive lead of the voltmeter to

the battery positive terminal post. Connect the nega-
tive lead of the voltmeter to the battery positive cable
terminal clamp (Fig. 5). Rotate and hold the ignition
switch in the Start position. Observe the voltmeter. If
voltage is detected, correct the poor connection
between the battery positive cable terminal clamp
and the battery positive terminal post.

(3) Connect the voltmeter to measure between the

battery positive cable terminal clamp and the starter
solenoid B(+) terminal stud (Fig. 6). Rotate and hold
the ignition switch in the Start position. Observe the
voltmeter. If the reading is above 0.2 volt, clean and
tighten the battery positive cable eyelet terminal con-
nection at the starter solenoid B(+) terminal stud.
Repeat the test. If the reading is still above 0.2 volt,
replace the faulty battery positive cable.

(4) Connect the voltmeter to measure between the

battery negative cable terminal clamp and a good
clean ground on the engine block (Fig. 7). Rotate and
hold the ignition switch in the Start position.
Observe the voltmeter. If the reading is above 0.2
volt, clean and tighten the battery negative cable
eyelet terminal connection to the engine block.
Repeat the test. If the reading is still above 0.2 volt,
replace the faulty battery negative cable.

Fig. 4 Test Battery Negative Connection Resistance

- Typical

1 – VOLTMETER
2 – BATTERY

Fig. 5 Test Battery Positive Connection Resistance -

Typical

1 – VOLTMETER
2 – BATTERY

Fig. 6 Test Battery Positive Cable Resistance -

Typical

1 – BATTERY
2 – VOLTMETER
3 – STARTER MOTOR

STARTING SYSTEMS

8B - 7

DIAGNOSIS AND TESTING (Continued)

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