JEEP CHEROKEE 1988 Service Repair Manual

system. For testing, see appropriate IGNITION SYSTEM CHECK
flow chart in COMPUTERIZED ENGINE CONTROLS section. For
diagnosis of HEI system, refer to following diagnostic
chart. See Fig. 11.
Fig. 11: Ignition Sys Check (HEI Only), Testing applies to HEI
sys with mechanical weights and vacuum advance.
Courtesy of General Motors Corp.
OVERHAUL

REASSEMBLY
Ensure pick-up assembly arm is correctly installed on pin. If
not, arm can float and cause ignition timing to vary. To prevent
corrosion, ensure module terminals are lubricated with petroleum jelly
before installation. To prevent heat damage, coat bottom of module and
module rest pad in housing with silicone grease. Before installation
of roll pin in driven gear, ensure timing mark on roll pin and rotor
tip align. See Figs. 12 through 14.
Fig. 12: Exploded View of HEI Distributor
Courtesy of General Motors Corp.

Fig. 13: Exploded View of HEI-EST Distributor With Sealed Connector
Courtesy of General Motors Corp.

Fig. 14: Exploded View of HEI Distributor Without Sealed Connector
Courtesy of General Motors Corp.

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IN STR UM EN T P A N EL - S TA N DAR D

1988 J e ep C hero ke e
1988 Switches & Instrument Panels
JEEP
DESCRIPTION & OPERATION
Instrument panel is composed of speedometer housing,
tachometer and instrument cluster gauges.
FUEL GAUGE
System consists of a fuel gauge, an in-tank sending unit, and
appropriate wiring. Fuel gauge is grounded through variable resistor
of sending unit. A float attached to a slide rheostat follows fuel
level and varying resistance increases or decreases indicator reading.
TEMPERATURE GAUGE
System consists of gauge and sending unit and appropriate
wiring. The gauge is grounded through variable resistor of sending
unit. Changes in coolant temperature vary resistance in sending unit,
increasing or decreasing indication on gauge.
VOLTMETER
The voltmeter indicates regulated voltage to provide an
indication of charging system's ability to maintain battery charge.
OIL PRESSURE GAUGE
The oil pressure gauge system consists of gauge and a
variable resistance sending unit. Gauge needle, attached to bi-
metallic strip, responds to temperature changes.
REMOVAL & INSTALLATION
INSTRUMENT CLUSTER
Removal & Installation
1) Disconnect negative battery cable. On models with cruise
control, reach behind instrument cluster and disconnect speedometer
cable from speed switch. See Fig. 1.
2) On models without cruise control, raise vehicle on hoist.
Disconnect speedometer cable from transfer case (or transmission) and
at frame rail bracket. Move speedometer cable forward and upward to
provide slack. Lower vehicle.
3) On all models, remove instrument panel bezel screws and
bezel. Remove screws attaching cigarette lighter and switch housings
to instrument panel. Move housings aside.
4) Remove screws attaching cluster to instrument panel and
carefully pull cluster and speedometer toward rear of vehicle.
Disconnect wiring harness connectors.
5) Squeeze speedometer cable locking tabs and disconnect
cable from speedometer. See Fig. 1. Remove instrument cluster. To
install, reverse removal procedure.

Fig. 1: Speedometer Cable Disconnect Points
Courtesy of Chrysler Motors.
SPEEDOMETER & TACHOMETER

Removal & Installation
Remove and disassemble instrument cluster. Remove
speedometer, tachometer, or gauge being serviced. To install, reverse
removal procedure.

JA C KIN G & H O IS TIN G

1988 J e ep C hero ke e
1988 Jacking & Hoisting
JEEP
HOISTING
FRAME CONTACT HOIST
Cherokee, Comanche, Wagoneer & Wrangler
Vehicle may be raised on single or twin-post swiveling arm
or ramp-type drive hoists. If using swiveling arm hoist, ensure
lifting pads are positioned evenly on frame rails at points "A" and
"B". Ensure lifting pads are not contacting transfer case or skid
plate. All hoists should be equipped with proper adapters to support
vehicle at frame rails only.
Grand Wagoneer
Vehicle may be raised on single or twin-post swiveling arm
or ramp-type drive hoists. If using swiveling arm hoist, ensure
lifting pads are positioned evenly on frame rails and lifting pads
are not contacting transfer case or skid plate. All hoists should be
equipped with proper adapters to support vehicle at frame rails only.
JACKING
FLOOR JACK
Cherokee, Comanche, Wagoneer & Wrangler
Vehicle may be raised by positioning jack at points "A" and
"B" only. Never attempt to raise the vehicle with the jack positioned
under the axle tubes, body side sills or front suspension arms. Use
the sub frame rail lift points only.
Grand Wagoneer
Vehicle may be raised by positioning jack under the front or
rear frame rails. Never place jack under front or rear axle tubes, or
under shock absorber mounting brackets.
Fig. 1: Hoisting & Jacking Points
Position lifting pads evenly on frame rails.

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LO CKIN G H UBS - A U TO M ATIC

1988 J e ep C hero ke e
1988 Locking Hubs - Command-Trac & Selec-Trac
Jeep
DESCRIPTION & OPERATION
Command-Trac locking hub is used on Model 30 front axles.
This system can be shifted between 2WD and 4WD high range while
vehicle is moving. The only time vehicle must be stopped to shift into
or out of 4WD is when shifter is in low range. See Fig. 1.
Selec-Trac locking hubs allow full or part time 4WD. Used on
Model 30 front axles, system can be shifted into 2WD or 4WD modes only
when vehicle is stopped. See Fig. 2.
Fig. 1: Command-Trac Vacuum Control System
TROUBLE SHOOTING
SELEC-TRAC SYSTEM
2WD To 4WD
Position mode select switch to "4WD" position while driving
vehicle 2-3 MPH. Axle should ratchet and clunk into position. Transfer
case should shift after axle shifts, accompanied by hissing sound from
mode selector switch.
4WD To 2WD
1) Position mode select switch to "2WD" position. Transfer
case should shift to 2WD and not allow shifting into 4WD or "LO"
range. Axle should shift after transfer case shifts.

2) To determine if front axle has completed a shift out of
4WD into 2WD, position mode select switch back to "4WD" position while
operating vehicle at slow speed. If vehicle shifts into 2WD, axle will
ratchet. If shift is not completed, transfer case will shift into 4WD
and hissing sound will come from mode select switch.
FRONT AXLE SHIFT MOTOR TEST
1) Disconnect vacuum harness from front axle shift motor.
Connect vacuum pump to shift motor front port. Apply 15 in. Hg vacuum
to shift motor. Rotate right front wheel to disengage axle.
2) Shift motor should hold vacuum at least 30 seconds. If
not, replace motor. If motor does hold vacuum, disconnect vacuum pump
from shift motor front port. Connect pump to shift motor rear port and
cap transfer case connecting port. Apply 15 in. Hg vacuum to motor.
3) Shift motor should hold vacuum for at least 30 seconds. If
not, replace motor. If motor does hold vacuum, remove cap from shift
motor transfer case connecting port and check for vacuum. If no vacuum
is present, rotate right front wheel to ensure axle has shifted
completely. Axle must completely shift to open shift motor connecting
port.
4) Recheck vacuum at shift motor transfer case port. If
vacuum is present, transfer case requires diagnosis. Command-Trac uses
Model 207 transfer case. Selec-Trac uses Model 228 transfer case.
REMOVAL & INSTALLATION
LOCKING HUB
Removal
1) Remove cover to outer clutch housing. Remove bearing race
spring assembly. Remove sealing ring and seal bridge retainer. Remove
bearing components.
2) Squeeze tangs of wire retaining ring together with needle-
nose pliers. Pull remaining components of automatic hub from wheel.
Installation
1) Ensure lock ring is in position. Using Bearing Nut Wrench
(J-6893-D), tighten wheel bearing adjusting nut to 50 ft. lbs. (60 N.\
m) to seat bearings.
2) Back off nut and tighten to 35 ft. lbs. (47 N.m) while
rotating hub. Finally, back off nut a maximum of 3/8 turn. Assemble
lock ring (with tab in keyway) over axle shaft, against bearing
adjustment nut.
3) Adjustment nut pin must pass through one of the washer
holes. Tighten outer adjusting nut to 183 ft. lbs. (248 N.m). Align
outer clutch housing splines with splines of wheel hub.
4) Loosen cover screws 3 or 4 turns, and push in on cover to
allow retaining ring to expand into rotor hub groove. Tighten cover
cap screws to 40-50 INCH lbs. (4.5-5.6 N.m).
Fig. 2: Selec-Trac Vacuum Control System
AXLE SHIFT MOTOR & HOUSING