JEEP CHEROKEE 1988 Service Repair Manual
Manufacturer: JEEP, Model Year: 1988, Model line: CHEROKEE, Model: JEEP CHEROKEE 1988Pages: 1378, PDF Size: 19.9 MB
Page 171 of 1378
* Switch to LOW
blower.
* Close doors. Too warm - Check control
lever operation, heater
water valve, cooling
system and gauge readings.
* Check outlet
temperature. 35-45
F (1.7-7.2 C)\
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Visual Check Visual Check Shows:
* Compressor Quiet, No Leaks Noisy - Check belts, oil
level, seals, gaskets,
reed valves.
* Condenser Free of Obstructions Blocked - Clean off.
Plugged - Flush or
replace.
* Receiver-Drier Dry and warm to Frosty - Check for re-
touch striction, replace
Desicant.
* Sight Glass Clear or few bubbles Bubbly, foamy or streaks -
Check gauge readings.
* High Side Lines Dry and warm to Frosty or very hot - Check
touch for restriction or
overcharge.
* Low Side Lines Dry and cool to Frosty or warm - Check for
touch restriction, low charge or
bad valve.
* Expansion Valve Dry Frosty - Check for moisture
or restriction. Check
sensing bulb.
* STV Dry and cool to Frosty or warm - Check
touch gauge readings for valve
malfunction.
* Evaporator Dry and cold to Freezing or warm - Check
touch expansion valve, STV or
thermo switch.
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Gauge Readings Gauge Readings are:
* High Side Gauge See Pressure Chart Above or below normal - See
A/C DIAGNOSIS.
* Low Side Gauge See Pressure Chart Above or below normal - See
A/C DIAGNOSIS.
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PRESSURE CHARTS
Page 172 of 1378
Fig. 4: Ambient Temperature/Pressure
Page 173 of 1378
![JEEP CHEROKEE 1988 Service Repair Manual Fig. 5: Evaporator Temperature/Pressure
A/C SYSTEM DIAGNOSIS WITH GAUGES
DIAGNOSIS WITH GAUGES - SYSTEMS WITH INSUFFICIENT OR NO COOLING\
\](/img/16/57037/w960_57037-172.png "JEEP CHEROKEE 1988 Service Repair Manual Fig. 5: Evaporator Temperature/Pressure
A/C SYSTEM DIAGNOSIS WITH GAUGES
DIAGNOSIS WITH GAUGES - SYSTEMS WITH INSUFFICIENT OR NO COOLING\
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Fig. 5: Evaporator Temperature/Pressure
A/C SYSTEM DIAGNOSIS WITH GAUGES
DIAGNOSIS WITH GAUGES - SYSTEMS WITH INSUFFICIENT OR NO COOLING\
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LOW SIDE HIGH SIDE OTHER SYMPTOMS(1) DIAGNOSIS
GAUGE GAUGE
Normal Normal No or few bubbles in sight Some Air and
glass. High side gauge may Moisture in System
go high. Low side gauge
does not fluctuate with
compressor on/off cycle.
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Normal Normal Cools okay in morning but Excessive Moisture
not during hot part of day. in System
Page 174 of 1378
![JEEP CHEROKEE 1988 Service Repair Manual Tiny bubbles in sight
glass. Discharge air warm
when low side gauge drops
into vacuum.
\](/img/16/57037/w960_57037-173.png "JEEP CHEROKEE 1988 Service Repair Manual Tiny bubbles in sight
glass. Discharge air warm
when low side gauge drops
into vacuum.
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Tiny bubbles in sight
glass. Discharge air warm
when low side gauge drops
into vacuum.
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Normal Normal Thermostatic switch system Defective Thermo-
only-compressor cycles off static Switch
and on too rapidly.
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Normal Normal Cycling clutch systems Misadjusted Thermo
to High only-Compressor doesn't static Switch or
turn on soon enough. Defective Pressure
Discharge air becomes Sensing Switch
warm as low side
pressure rises.
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Low Low Bubbles in sight glass. Low R-12 Charge
Outlet air slightly cool.
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Low Low Sight glass clear or oil- Excessively Low
streaked. Outlet air very R-12 Charge
warm.
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Low Low Outlet air slightly cool. Expansion Valve
Sweating or frost at Stuck Closed.
expansion valve. Screen Plugged or
Sensing Bulb
Malfunction
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Low Low Outlet air slightly cool. Restriction on
High side line cool to High Side.
touch. Sweating or frost
on high side.
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Low High Evaporator outlet pipe STV Stuck Open
cold. Low side goes into
vacuum when blower is
disconnected.
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High Low Evaporator outlet pipe STV Stuck Open
warm. Outlet air warm.
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High Low Noise from compressor Compressor
Malfunction
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High High Outlet air warm. Condenser
Liquid line very hot. Malfunction or
Bubbles in sight glass. R-12 Overcharge
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High High Outlet air slightly cool. Large Amount of
Bubbles in sight glass. Air and Moisture
in System.
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High High Outlet air warm. Expansion Valve
Evaporator outlet Stuck Open.
sweating and frost.
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(1) - If equipped with a low refrigerant charge protection system,
compressor operation may have stopped.
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A/C SYSTEM SERVICE SPECIFICATIONS
Page 175 of 1378
![JEEP CHEROKEE 1988 Service Repair Manual REFRIGERANT OIL & R-12 CAPACITY TABLE\
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\](/img/16/57037/w960_57037-174.png "JEEP CHEROKEE 1988 Service Repair Manual REFRIGERANT OIL & R-12 CAPACITY TABLE\
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REFRIGERANT OIL & R-12 CAPACITY TABLE\
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(1) Oil R-12
Application Ounces Ounces
Eagle ......................... 5.7 ........................... 36
(1) - Total system capacity, unless otherwise noted.
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SYSTEM REFRIGERANT CAPACITIES\
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Application Pounds Ounces
Eagle
Medallion & Premier ..... 1 7/8 .............. 29
Summit (FX105V) ......... 2 1/4 .............. 36
Jeep
CJ Models ............... 2 1/2 .............. 40
Comanche .................. 2 ................ 32
All Other Jeep Models . 2 1/4 .............. 36
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COMPONENT OIL REPLACEMENT QUANTITIES\
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Component Ounces
Accumulator ................................... (1)
Condenser ....................................... 1
Evaporator ...................................... 1
Receiver-Drier .................................. 1
Compressor
Premier ....................................... (1)
Medallion ..................................... 5.7
Grand Wagoneer .................................. 8
All Other Jeep Models ........................... 7
(1) - Add amount drained plus 1 ounce.
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COMPRESSOR BELT TENSION (Lbs.) (1)\
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Application New Belt Used Belt
Eagle
1.4L & 1.7L ............ 120-160 ......... 90-115
Jeep
Regular Belt ........... 125-155 ......... 90-115
Serpentine Belt ........ 180-200 ........ 140-160
(1) - Using standard strand tension gauge.
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COOLING SYSTEM CAPACITIES (1)\
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Application Quarts (Liters)
Eagle
Medallion & Premier
With A/C .............................. 4.8 (4.5)
Page 176 of 1378
Without A/C ........................... 4.4 (4.2)
Jeep
Cherokee & Wagoneer (2)
4-Cylinder ........................... 10.0 (9.5)
V6 .................................. 12.0 (11.4)
CJ & Scrambler
4-Cylinder ............................ 9.0 (8.5)
6-Cylinder ........................... 10.5 (9.9)
Grand Wagoneer & Truck (3)
6-Cylinder .......................... 12.5 (11.8)
V8 .................................. 15.5 (14.7)
(1) - May vary +/- 15% due to system variations.
(2) - Includes 2.3 qts. (2.2L) in recovery bottle.
(3) - Includes 1 qt. (.9L) for heater.
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Page 177 of 1378
\003
AIR C LE A N ER - T H ER M OSTA TIC
1988 J e ep C hero ke e
1988 Exhaust Emission Systems
JEEP THERMOSTATIC AIR CLEANER
DESCRIPTION
On models equipped with carburetor, a system for pre-heating
air entering carburetor is used. This system is part of the air
cleaner and maintains air temperature at a point where carburetor can
be calibrated at leaner setting to reduce hydrocarbon emissions and
improve driveability during warm-up.
These systems are vacuum-operated and consist of heat shroud
on exhaust manifold, hot air duct, thermal sensor switch, vacuum
motor, air valve assembly and reverse delay valve.
Fig. 1: Thermostatic Air Cleaner (TAC) Assembly
Courtesy of Chrysler Motors.
OPERATION
Page 178 of 1378
During engine warm-up, temperature sensor switch applies
vacuum to vacuum motor. Air diverter valve is held to "ON" position.
Exhaust manifold heated air flows to air cleaner. As temperature of
incoming air increases to 90
F (32 C), temperature sensor opens
vacuum line to atmosphere allowing spring pressure to push valve to
"OFF" position. Air now flows from outside, through air cleaner duct
to carburetor.
AIR CLEANER TRAP DOOR
On California vehicles, spring-loaded trap door is built
into air cleaner to close off air cleaner when engine is shut off.
Door is vacuum operated.
REVERSE DELAY VALVE
Reverse delay valve is installed in vacuum line in some
vehicles to prevent trap door from closing during low engine vacuum
periods. Valve provides about 9 seconds delay before allowing trap
door to close.
Fig. 2: Cutaway View of Thermostatic Air Cleaner Assembly
Courtesy of Chrysler Motors.
Page 179 of 1378
TESTING
VACUUM MOTOR & TEMPERATURE SENSOR
1) Remove air cleaner assembly from vehicle and allow to
cool to room temperature. Look through air cleaner duct and observe
position of air diverter valve. It should be fully open to outside
air.
2) Reinstall assembly on carburetor and connect hot air duct
and manifold vacuum hose. Start engine and observe position of air
valve in snorkel. It should be fully closed to outside air.
3) Move throttle lever rapidly to 1/2 to 3/4 opening and
release. Air diverter valve should open and then close again. Allow
engine to warm to operating temperature and observe position of air
valve in snorkel. It should be fully open to outside air.
4) If valve does not move to fully close off outside air at
83
F (28 C) or less with vacuum applied, check for binding of duct,
vacuum leaks in hose connections or disconnected vacuum motor. If
valve mechanism operates freely and no vacuum leaks are detected,
connect hose from intake manifold vacuum source directly to vacuum
motor.
5) If air valve now moves to close off outside air, replace
thermal sensor switch. If valve still does not move to close off
outside air, replace air cleaner assembly and vacuum motor assembly.
TRAP DOOR
1) With engine off, remove air cleaner and check position of
trap door. It should be closed.
2) Remove vacuum hose from intake manifold vacuum source and
apply an external vacuum source of approximately 2-4 in. Hg vacuum.
Trap door should open.
3) If door does not open, apply vacuum directly to vacuum
motor. If door does not open, check for binding and adjust as
necessary. If door swings freely, replace vacuum motor.
4) If door opens during step 3), check vacuum hose for
blockage, cracks or leaks. Correct as necessary and retest as
specified in step 2).
5) If hoses are not defective, remove reverse delay valve,
join vacuum hose and retest from step 2). If door opens, replace
reverse delay valve.
REVERSE DELAY VALVE
1) Connect external vacuum source to port on White side of
delay valve. Connect one end of 24" (610 mm) section of rubber hose
to vacuum gauge and other end to port on colored side of valve.
2) With a constant 10 in. Hg vacuum applied, note time
required for vacuum gauge pointer to move from 0-8 in. Hg.
Page 180 of 1378
AIR IN JE C TIO N S YSTE M
1988 J e ep C hero ke e
1988 Exhaust Emission Systems
JEEP PULSE AIR INJECTION SYSTEM
4.2L
DESCRIPTION
Pulse air injection system is used to inject fresh air into
exhaust system. When fresh air is injected into hot exhaust gases,
combustion takes place. This reduces amount of unburned fuel that
escapes into the atmosphere.
System consists of check valves, control valves, control
valve solenoids, vacuum reservoir, vacuum lines and air lines. Pulse
air system is capable of injecting air at both catalytic converter
(downstream) or at front exhaust pipe.
OPERATION
Pulse air system uses alternating positive and negative
pressure pulsations in exhaust system to draw in fresh air through
air cleaner. Check valves are used to allow fresh air into exhaust,
but prevent exhaust from flowing back into intake system.
Air is switched between upstream and downstream injection by
2 vacuum-operated control valves. Each control valve is switched by
an electrically operated-vacuum solenoid.
Vacuum solenoids are switched on and off by MCU according to
engine operating conditions. Vacuum storage tank maintains vacuum
supply to switching solenoids.
DIAGNOSIS & TESTING
1) Check condition of all hoses and lines in system. Reroute
any kinked or restricted hoses. Repair or replace any cracked or
broken hoses. To check system operation, feel for suction in
injection hoses at air cleaner.
2) If problem exists, check to see if vacuum is being
supplied to the valve. If vacuum is not present at valve(s), check
vacuum lines or ports.