ad blue JEEP CHEROKEE 1988 Service User Guide

the old insert and machining an oversize insert bore. Replacement
oversize insert is usually chilled and the cylinder head is sometimes
warmed. Valve seat is pressed into the head. This operation requires
specialized machine shop equipment.
Valve Seat Concentricity
Using dial gauge, install gauge pilot in valve guide.
Position gauge arm on the valve seat. Adjust dial indicator to zero.
Rotate arm 360 degrees and note reading. Runout should not exceed
specification.
To check valve-to-valve seat concentricity, coat valve face
lightly with Prussian Blue dye. Install valve and rotate it on valve
seat. If pattern is even and entire seat is coated at valve contact
point, valve is concentric with the seat.
REASSEMBLY
Valve Stem Installed Height
Valve stem installed height must be checked when new valves
are installed or when valves or valve seats have been ground. Install
valve in valve guide. Measure distance from tip of valve stem to
spring seat. See Fig. 11. Distance must be within specifications.
Fig. 11: Measuring Valve Stem Installed Height - Typical
This Graphic For General Information Only
Remove valve and grind valve stem tip if height exceeds
specification. Valve tips are surface hardened. DO NOT remove more

SPARK PLUG CHECK
Faulty or fouled plugs may perform well at idle speed, but at
higher engine speeds, they frequently fail. Faulty plug can exhibit
the following symptoms:
* Poor fuel economy.
* Power loss.
* Decreased engine speed.
* Hard starting.
* Generally poor performance.
Spark plugs also malfunction due to carbon fouling,
excessive electrode air gap, or broken insulators.
SYNC PULSE SIGNAL GENERATOR (STATOR) TEST
NOTE: For this test, an analog voltmeter MUST be used.
1) Insert the positive (+) lead of the voltmeter into the
Blue wire at the distributor connector.
2) Insert the negative (-) voltmeter lead into the Gray/Whit\
e
wire at the distributor connector.
CAUTION: DO NOT remove the distributor connector from distributor.
Insert the voltmeter leads into the backside of the
distributor connector to make contact with the terminals.
3) Set the voltmeter to the 15-Volt D/C scale. Turn ignition
key to "ON".
4) The voltmeter should display approximately 5.0 volts.
5) If no voltage displays, check that the voltmeter leads are
making good contact. If there is still no voltage, go to next step.
6) Remove the ECU and check for voltage at pin "C-16" and
ground with harness connected. If there in still no voltage, proceed
to the next step.
7) Connect Diagnostic Tester M.S. 1700 to the vehicle. Using
the diagnostic tester, perform vehicle test. If voltage is present, go
to the next step.
8) Check for continuity between the Blue wire at the
distributor connector and pin C-16 at the ECU.
9) If there in no continuity, repair harness as necessary.
10) Check for continuity between the Gray/White wire at the
distributor connector and pin C-5 at the ECU.
11) If there is no continuity, repair harness as necessary.
12) Check for continuity between the Black wire at the
distributor connector and ground.
13) If there is no continuity, repair harness as necessary.
14) While observing the voltmeter, crank the engine; the
voltmeter needle should fluctuate back and forth while the engine in
cranking. A fluctuation verifies that the stator in the distributor is
operating properly.
15) If there is no pulse sync, replace the stator. Refer to
REMOVAL & INSTALLATION below in this article.
REMOVAL & INSTALLATION
COOLANT TEMPERATURE SENSOR (CTS)
Removal
1) Drain the cooling system.

Electronic Spark Timing (EST) is used on most computer
controlled systems. The Electronic Control Module (ECM) monitors
information from various engine sensors, computes desired spark
timing, and signals distributor for correct timing change. The HEI
distributor with EST does not have centrifugal advance weights,
springs, or a vacuum advance unit. See Figs. 2 and 3.
HEI & EST WITH ELECTRONIC SPARK CONTROL (ESC)
All fuel injected vehicles are equipped with Electronic Spark
Control (ESC). ESC systems contain a knock sensor mounted in the
engine block. A Blue wire connects the sensor to the ESC module. If
the sensor detects knock, it sends a signal to the module which, in
turn, signals the ECM. The ECM sends a signal to the distributor to
retard spark timing.
Fig. 2: Typical HEI/EST Distributor, Integral coil system shown.
Courtesy of General Motors Corp.
OPERATION

TU RN S IG NALS & H AZA R D F LA SH ER S

1988 J e ep C hero ke e
1988 Turn Signal & Hazard Light Systems
JEEP
DESCRIPTION
Turn signals and hazard flashers systems use a common turn
signal/hazard light switch assembly mounted within upper steering
column housing.
FLASHER LOCATIONS
Hazard
Mounted on fuse block.
Turn Signal
Mounted on fuse block.
TROUBLE SHOOTING
NOTE: Following trouble shooting is only information available
from manufacturer.
Hazard Lights (Comanche, Cherokee & Wagoneer)
If lights do not come on with hazard switch turned on, check
hazard/stop light fuse by operating stop lights. If fuse is okay,
check turn signal flasher, turn signal/hazard switch, and related
wiring. If only one hazard light does not work, check bulb.
Turn Signals (Comanche, Cherokee & Wagoneer)
If all turn signals do not work, check turn/back-up light
fuse by operating back-up lights. If fuse is okay, check turn signal
flasher, turn signal/hazard switch, and related wiring. If only one
turn signal does not work, check bulb.
TESTING
NOTE: Following trouble shooting is only information available
from manufacturer.
Hazard Indicators (Wrangler)
1) Turn ignition and hazard warning switch "ON". Check for
pulsating voltage at Light Blue (left indicator) and Dark Blue (right\
indicator) wires. If voltage is present, go to next step. If voltage
is not present, replace turn signal switch.
2) Remove bulbs for turn signal indicators. Measure
resistance across bulb terminals. If resistance is zero ohms, replace
light bulb(s). If resistance readings are not zero ohms, go to next
step.
3) Check for pulsating voltage at battery side of bulb
sockets. If voltage is present, go to next step. If voltage is not
present, repair open circuit between socket and turn signal switch
steering column connector.
4) Turn ignition off and check resistance on ground side of
bulb sockets. If resistance is zero ohms, hazard indicator circuit is
okay. If resistance reading is not zero ohms, repair open in ground
circuit.
Hazard Lights (Wrangler)

1) Check operation of stop lights. If stop lights come on, go
to next step. If not, check hazard/stop light fuse. If fuse is okay,
check for voltage on battery side of hazard/stop light fuse. If
voltage is not present, repair open circuit between fusible link and
fuse block.
2) Remove hazard flasher and check for voltage on battery
side of hazard flasher at fuse block. If voltage is present, go to
next step. If voltage is not present, repair open circuit to fuse
block.
3) Measure resistance across turn signal flasher terminals.
If resistance across flasher is zero ohms, replace flasher. If
resistance is other than zero ohms, install flasher and turn ignition
on.
4) Check for voltage at Brown wire of turn signal switch
steering column connector. If voltage is present, go to next step. If
voltage is not present, repair open circuit between flasher and turn
signal switch connector.
5) Turn hazard warning switch "ON". Check for pulsating
voltage at Light Blue, Dark Blue, Yellow, and Dark Green wires. If
voltage is present, hazard light circuit is okay. If voltage is not
present, replace turn signal switch.
Turn Signals (Wrangler)
1) Turn ignition on and check operation of back-up lights. If
lights come on, go to step 3). If back-up lights do not come on, check
turn signal/back-up light fuse.
2) If fuse is okay, check for voltage at battery side of turn
signal/back-up light fuse. If voltage is not present, repair open
circuit between fuse block and ignition switch. If voltage is present,
go to next step.
3) Remove turn signal flasher and measure resistance across
flasher terminals. If resistance across flasher is zero ohms, replace
turn signal flasher. If flasher is okay, install flasher and turn
ignition on.
4) Check for voltage on battery side of flasher at fuse
block. If voltage is present, go to next step. If voltage is not
present, repair open circuit to fuse block.
5) Disconnect turn signal switch at steering column
connector. Place turn signal switch in left turn position and measure
resistance between Yellow and Purple wires. If resistance across wires
is zero ohms, replace turn signal switch. If resistance is other than
zero ohms, go to next step.
6) Place turn signal switch in right turn position and
measure resistance between Dark Green and Purple wires. If resistance
across wires is zero ohms, replace turn signal switch. If resistance
is other than zero ohms, turn signal circuit is okay.
Turn Signal Indicators (Wrangler)
1) Turn ignition on. Place turn signal switch in left turn
position and check for pulsating voltage at Light Blue wire. If
voltage is present, go to next step. If voltage is not present,
replace turn signal switch.
2) Place turn signal switch in right turn position and check
for pulsating voltage at Dark Blue wire. If voltage is not present,
replace turn signal switch. If voltage is present, go to next step.
3) Remove bulbs from turn signal indicators. Measure
resistance across bulb terminals. If resistance is zero ohms, replace
light bulb(s). If resistance readings are not zero ohms, turn ignition\
on.
4) Place turn signal switch in left and right turn position
and check for pulsating voltage at battery side of bulb sockets. If
voltage is present, go to next step. If voltage is not present, repair
open circuit between socket(s) and steering column connector.

\003
WIP ER /W ASH ER S YSTE M

1988 J e ep C hero ke e
1988 Wiper/Washer Systems
JEEP
All Models
DESCRIPTION
Jeep vehicles use a 2-speed electric motor, which is a
compound wound (series and shunt) type. A crank arm, attached
externally to gear shaft, operates linkage which activates wiper
blades.
All models have an optional intermittent feature. All models
use an electric washer system consisting of a motor, reservoir, and
necessary hoses and nozzles.
Some Cherokee and Wagoneer models are equipped with rear
wipers. The rear motor is a single-speed motor with an automatic park
feature. The circuit is protected by a separate 4.5-amp circuit
breaker attached to brake pedal support.
TROUBLE SHOOTING
WIPER INOPERATIVE OR OPERATES AT ONE SPEED ONLY
1) If wiper does not operate on either speed, check for
binding or interference of linkage. If okay, place wiper switch on
"LO" and then on "HI" setting. Connect a test light between terminals
of wiring harness plug that connects to motor.
2) Check for power at White wire with tracer and Black
(ground) wire terminal for low speed. Check between Dk. Blue with
tracer and Black wire terminal for high speed.
3) If light does not glow, check ignition switch, wiper
switch, harness or terminals for open circuits. If light glows, check
for loose or misaligned connection between wiring harness plug and
motor plug. If okay, replace wiper motor.
WIPERS DO NOT PARK
1) Disconnect motor and connect Gray lead to White lead.
Apply 12 volts to Blue lead. Replace motor if it fails to park. If it
parks, turn ignition switch on, and wiper switch to "PARK".
2) Connect a test light to Lt. Green wire with tracer and to
ground at motor plug.
3) Check continuity between Tan wire with tracer and White
wire with tracer.
4) If test light does not glow, check harness connections
between motor and instrument panel switch. If okay, replace panel
switch. If not okay, repair harness connection.
WIPER MOTOR QUITS WHILE WIPING
1) With engine idling and blower motor on high, operate
wipers at high speed setting for 5 cycles consisting of 3 seconds of
water and 57 seconds of drying.
2) If motor struggles to a complete stop, clean glass and
replace blades. Repeat test. If motor stops, test circuit breaker in
panel switch. If motor stopped suddenly in original test, check
circuit breaker. Repeat test. If motor stops, replace motor.

Fig. 2: Identifying Option Symbols
COLOR ABBREVIATIONS IDENTIFICATION
COLOR ABBREVIATIONS








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Color Normal Optional
Black .................. BLK ................... BK
Blue ................... BLU ................... BU
Brown .................. BRN ................... BN
Clear .................. CLR ................... CR
Dark Blue ............ DK BLU ............... DK BU
Dark Green ........... DK GRN ............... DK GN
Green .................. GRN ................... GN
Gray ................... GRY ................... GY
Light Blue ........... LT BLU ............... LT BU
Light Green .......... LT GRN ............... LT GN
Orange ................. ORG ................... OG
Pink ................... PNK ................... PK
Purple ................. PPL ................... PL
Red .................... RED ................... RD
Tan .................... TAN ................... TN