Jeep Liberty KJ. Manual - part 27

The Battery, Starting, and Charging systems operate in conjunction with one another, and must be tested as a com-
plete system. For correct operation of starting/charging systems, all components used in these 3 systems must per-
form within specifications. When attempting to diagnose any of these systems, it is important that you keep their
interdependency in mind.

The diagnostic procedures used in each of these groups 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, volt/ohmmeter, battery charger, carbon pile rheostat (load tester), and 12-volt
test lamp may be required.

Certain starting system components are monitored by the PCM and may produce a Diagnostic Trouble Code (DTC).

OPERATION

The starting system components form two separate circuits. A high-amperage feed circuit that feeds the starter
motor between 150 and 350 amperes (700 amperes - diesel engine), and a low-amperage control circuit that oper-
ates 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 clutch pedal position switch (manual transmission), the park/neutral position switch
(automatic transmission), the starter relay, the electromagnetic windings of the starter solenoid, and the connecting
wire harness components.

If the vehicle is equipped with a manual transmission, it has a clutch pedal position switch installed in series
between the ignition switch and the coil battery terminal of the starter relay. This normally open switch prevents the
starter relay from being energized when the ignition switch is turned to the momentary Start position, unless the
clutch pedal is depressed. This feature prevents starter motor operation while the clutch disc and the flywheel are
engaged. The starter relay coil ground terminal is always grounded on vehicles with a manual transmission.

If the vehicle is equipped with an automatic transmission, battery voltage is supplied through the low-amperage
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 position 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 normally 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 sole-
noid coil windings.

The energized solenoid pull-in coil pulls in the solenoid 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 manual
transmission flywheel or on the automatic transmission torque converter or torque converter 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 solenoid 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 protects 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

STARTING SYSTEM

8F - 47

relay coil is de-energized. This causes the relay contacts to open. When the relay contacts open, the starter sole-
noid plunger hold-in coil is de-energized.

When the solenoid plunger hold-in coil is de-energized, the solenoid plunger return spring returns the plunger to its
relaxed position. This causes the contact disc to open the starter feed circuit, and the shift lever to disengage the
overrunning clutch and pinion gear from the starter ring gear.

DIAGNOSIS AND TESTING - STARTING SYSTEM

The battery, starting, and charging systems operate in conjunction with one another, and must be tested as a com-
plete system. For correct starting/charging system operation, all of the components involved in these 3 systems
must perform within specifications.

Starting System Diagnosis

CONDITION

POSSIBLE CAUSE

CORRECTION

STARTER FAILS TO
OPERATE.

1. Battery discharged or
faulty.

1. Refer to Battery. Charge or replace battery, if required.

2. Starting circuit wiring
faulty.

2. Refer to 8, Wiring Diagrams. Test and repair starter
feed and/or control circuits, if required.

3. Starter relay faulty.

3. Refer to Starter Relay in Diagnosis and Testing.
Replace starter relay if required.

4. Ignition switch faulty.

4. Refer to Ignition Switch and Key Lock Cylinder.
Replace ignition switch if required.

5. Clutch pedal position
switch faulty.

5. Refer to Clutch Pedal Position Switch.

6. Park/Neutral position
switch faulty or
misadjusted.

6. Refer to Park/Neutral Position Switch. Replace
park/neutral position switch if required.

7. Starter solenoid faulty.

7. Refer to Starter Motor. Replace starter motor assembly
if required.

8. Starter motor faulty.

8. If all other starting system components and circuits test
OK, replace starter motor.

STARTER ENGAGES,
FAILS TO TURN
ENGINE.

1. Battery discharged or
faulty.

1. Refer to Battery. Charge or replace battery if required.

2. Starting circuit wiring
faulty.

2. Refer to 8, Wiring Diagrams. Test and repair starter
feed and/or control circuits if required.

3. Starter motor faulty.

3. If all other starting system components and circuits test
OK, replace starter motor assembly.

4. Engine seized.

4. Refer to Engine Diagnosis in the Diagnosis and Testing
section of 9, Engine.

STARTER ENGAGES,
SPINS OUT BEFORE
ENGINE STARTS.

1. Starter ring gear faulty.

1. Refer to Starter Motor Removal and Installation.
Remove starter motor to inspect starter ring gear.
Replace starter ring gear if required.

2. Starter motor faulty.

2. If all other starting system components and circuits test
OK, replace starter motor assembly.

STARTER DOES NOT
DISENGAGE.

1. Starter motor
improperly installed.

1. Refer to Starter Motor Removal and Installation.
Tighten starter mounting hardware to correct torque
specifications.

2. Starter relay faulty.

2. Refer to Starter Relay Diagnosis and Testing. Replace
starter relay if required.

3. Ignition switch faulty.

3. Refer to Ignition Switch and Key Lock Cylinder.
Replace ignition switch if required.

4. Starter motor faulty.

4. If all other starting system components and circuits test
OK, replace starter motor.

8F - 48

STARTING SYSTEM

INSPECTION

For complete starter wiring circuit diagrams, refer to 8, Wiring Diagrams. Before removing any unit from starting
system for repair or diagnosis, perform the following inspections:

WARNING: On vehicles equipped with airbags, refer to 8, passive restraint systems, before attempting any
steering wheel, steering column, or instrument panel component diagnosis or service. Failure to take the
proper precautions could result in accidental airbag deployment and possible personal injury.

•

Battery - Visually inspect battery for indications of physical damage and loose or corroded cable connections.
Determine state-of-charge and cranking capacity of battery. Charge or replace battery if required. Refer to Bat-
tery in 8, Battery. Note: If equipped with diesel engine, a dual battery system may be used, and both
batteries must be inspected.

•

Ignition Switch - Visually inspect ignition switch for indications of physical damage and loose or corroded wire
harness connections. Refer to Ignition Switch and Key Lock Cylinder.

•

Clutch Pedal Position Switch - If equipped with manual transmission, visually inspect clutch pedal position
switch for indications of physical damage and loose or corroded wire harness connections. Refer to Clutch
Pedal Position Switch in 6, Clutch.

•

Park/Neutral Position Switch - If equipped with automatic transmission, visually inspect park/neutral position
switch for indications of physical damage and loose or corroded wire harness connections. Refer to Park/Neu-
tral Position Switch in 21, Transmission.

•

Starter Relay - Visually inspect starter relay for indications of physical damage and loose or corroded wire
harness connections.

•

Starter Motor - Visually inspect starter motor for indications of physical damage and loose or corroded wire
harness connections.

•

Starter Solenoid - Visually inspect starter solenoid for indications of physical damage and loose or corroded
wire harness connections.

•

Wiring - Visually inspect wire harnesses for damage. Repair or replace any faulty wiring, as required. Refer to
8, Wiring Diagrams.

TESTING

COLD CRANKING TEST

For complete starter wiring circuit diagrams, refer to 8,
Wiring Diagrams. The battery must be fully-charged
and load-tested before proceeding. Refer to Battery in
Battery.

1. Connect volt-ampere tester to battery terminals (1),

(2) and (3). See instructions provided by manufac-
turer of volt-ampere tester being used. Note: Cer-
tain diesel equipped models use dual batteries.
If equipped with dual battery system, tester
should be connected to battery on left side of
vehicle only. Also, tester current reading must
be taken from positive battery cable lead that
connects to starter motor.

2. Fully engage parking brake.

3. If equipped with manual transmission, place gear-

shift selector lever in Neutral position and block
clutch pedal in fully depressed position. If equipped with automatic transmission, place gearshift selector lever in
Park position.

4. Verify that all lamps and accessories are turned off.

5. To prevent a gasoline engine from starting, remove Automatic ShutDown (ASD) relay. To prevent a diesel engine

from starting, remove Fuel Pump Relay. These relays are located in Power Distribution Center (PDC). Refer to
label on PDC cover for relay location.

STARTING SYSTEM

8F - 49

Content .. 25 26 27 28 ..