1988 JEEP CHEROKEE Service Repair Manual

1) Disconnect pick-up coil leads from HEI/EST module
terminals "N" and "P". Set ohmmeter to middle scale and connect one
lead to either pick-up coil lead and the other lead to distributor
housing. See Fig. 9. Flex pick-up coil leads by hand to check for
intermittent shorts to ground. Reading should be infinity at all
times. If not, replace pick-up coil.
2) Connect ohmmeter between both pick-up coil leads. Check
for intermittent opens by flexing wires and connectors. Resistance
should be 500-1500 ohms. If not, replace pick-up coil.
Fig. 9: Checking Distributor Pick-Up Coil, Integral coil system
shown. External coil testing is similar
Courtesy of General Motors Corp.

Fig. 10: Integral Coil Spark Tester (ST-125) Hook-Up
Courtesy of General Motors Corp.
NOTE: Diagnosis of HEI systems with EST and EST/ESC require
thorough understanding of Computer Command Control (CCC)

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