1991 MITSUBISHI MONTERO check engine light

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A/C C O M PR ESSO R O IL C HEC KIN G

1991 M it s u bis h i M onte ro
1991 GENERAL SERVICING
Compressor Refrigerant Oil Checking
ISOLATING COMPRESSOR
NOTE: Only compressors with stem-type service valves can be
isolated.
1) Connect service gauge set to the compressor service valves
and open compressor valves slightly (turn in clockwise). Start engine
and operate air conditioning. Slowly turn compressor suction valve
clockwise toward closed (front-seated) position.
2) When suction pressure is reduced to zero or less, turn off
engine and compressor and quickly turn suction valve stem in to full
front-seated position. Suction pressure should be slightly above zero.
Turn discharge valve into front-seated position.
3) To check oil level, slowly open compressor crankcase plug
to relieve any remaining pressure. After oil level is corrected, cap
service gauge ports on both valves. Back-seat suction service valve to
allow refrigerant to enter compressor. Open discharge valve halfway.
4) Loosen discharge service valve cap, allowing refrigerant
pressure to force air out of compressor. Back-seat service valve and
tighten cap. Compressor is now ready for operation.
REFRIGERANT OIL
Only new, pure, moisture-free refrigerant oil should be used
in the air conditioning system. This oil is highly refined and
dehydrated to a point where moisture content is less than 10 parts per
million. The oil container must be tightly closed at all times when
not in use, or moisture will be absorbed into the refrigerant oil from
the air.
SERVICING PRECAUTIONS
NOTE: Recent findings by the EPA indicate that refrigerant is
harmful to the earth's protective Ozone layer. When
discharging refrigerant, DO NOT allow refrigerant to enter
the atmosphere. If available, use refrigerant
recovery/recycle systems when discharging system. Always
follow manufacturer's instructions.
DISCHARGING SYSTEM PRECAUTIONS
If compressor has stem-type service valves, it can be
isolated and removed without discharging entire system. See ISOLATING
COMPRESSOR at the beginning of this article. Otherwise, discharge
system completely before loosening any fittings.
DISCONNECTING LINES & FITTINGS TEST
After system is discharged, carefully clean area around all
fittings to be opened. Always use 2 wrenches when tightening or
loosening fittings to avoid twisting or distorting lines. Cap or plug
all openings as soon as lines are removed. DO NOT remove caps until
immediately before connections are made. This will keep entry of air

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A/C C O M PR ESSO R S ER VIC IN G

1991 M it s u bis h i M onte ro
1991 GENERAL SERVICING
Compressor Service
* PLEASE READ THIS FIRST *
CAUTION: When discharging air conditioning system, use only approved
refrigerant recovery/recycling equipment. Make every attempt
to avoid discharging refrigerant into the atmosphere.
ISOLATING COMPRESSOR
NOTE: Only compressors with stem-type service valves can be
isolated.
1) Connect service gauge set to the compressor service valves
and open compressor valves slightly (turn in clockwise). Start engine
and operate air conditioning. Slowly turn compressor suction valve
clockwise toward closed (front-seated) position.
2) When suction pressure is reduced to zero or less, turn off
engine and compressor and quickly turn suction valve stem in to full
front-seated position. Suction pressure should be slightly above zero.
Turn discharge valve into front-seated position.
3) To check oil level, slowly open compressor crankcase plug
to relieve any remaining pressure. After oil level is corrected, cap
service gauge ports on both valves. Back-seat suction service valve to
allow refrigerant to enter compressor. Open discharge valve halfway.
4) Loosen discharge service valve cap, allowing refrigerant
pressure to force air out of compressor. Back-seat service valve and
tighten cap. Compressor is now ready for operation.
REFRIGERANT OIL
Only new, pure, moisture-free refrigerant oil should be used
in the air conditioning system. This oil is highly refined and
dehydrated to a point where moisture content is less than 10 parts per
million. The oil container must be tightly closed at all times when
not in use, or moisture will be absorbed into the refrigerant oil from
the air.
DISCHARGING SYSTEM PRECAUTIONS
CAUTION: When discharging air conditioning system, use only approved
refrigerant recovery/recycling equipment. Make every attempt
to avoid discharging refrigerant into the atmosphere.
If compressor has stem-type service valves, it can be
isolated and removed without discharging entire system. Otherwise,
discharge system completely using approved refrigerant
recovery/recycling equipment before loosening any fittings.
DISCONNECTING LINES & FITTINGS TEST
After system is discharged, carefully clean area around all
fittings to be opened. Always use 2 wrenches when tightening or
loosening fittings to avoid twisting or distorting lines. Cap or plug
all openings as soon as lines are removed. Do not remove caps until

terminal "B" and negative lead to positive battery terminal. Reconnect
negative battery cable.
3) Start engine. Turn accessories on and adjust engine speed
until ammeter indicates 20 amps, and note voltmeter reading. If
voltmeter indicates .2 volt or less, system is okay.
4) If voltage is greater than .2 volt, wiring is defective
between alternator terminal "B", fusible link and battery positive
terminal. Disconnect negative battery cable, and remove test
equipment.
ALTERNATOR OUTPUT TEST
NOTE: During alternator output test, a slightly discharged battery
should be used as a fully charged battery may not allow full
alternator output.
1) Turn ignition switch to OFF position. Disconnect negative
battery cable. Disconnect alternator output wire from terminal "B".
Install positive lead of 100-amp ammeter to terminal "B" and negative
lead to disconnected output lead.
CAUTION: Tighten each connection securely as heavy current flow will
exist. DO NOT use clips on ammeter.
2) Connect positive voltmeter lead (0-20 volts) to alternato\
r
terminal "B" and negative lead to ground. Install tachometer, and
reconnect negative battery cable.
3) Ensure voltmeter indicates battery voltage. If no voltage
exists, an open circuit is present in wire between alternator terminal
"B" and battery negative terminal. Check grounds and fusible link.
4) Turn headlights on, and start engine. Set headlights at
high beam and heater switch on HIGH. Quickly accelerate engine speed
to 2500 RPM and note alternator output current registered on the
ammeter. Minimum output should be within specification. Refer to the
ALTERNATOR MINIMUM OUTPUT SPECIFICATIONS table.
NOTE: Output voltage changes with electrical load and temperature.
Ensure proper electrical load is applied while checking
output. Nominal output may not be obtained if alternator or
ambient temperature is excessive. Allow to cool, and recheck
output. Alternator output is stamped on metal plate attached
to alternator case.
5) If minimum output is not obtained and alternator wiring is
okay, repair alternator. Disconnect negative battery cable, and remove
test equipment.
REGULATED VOLTAGE TEST
NOTE: Ensure battery is fully charged and proper drive belt
tension exists.
1) Turn ignition switch to OFF position. Disconnect negative
battery cable. Install a digital voltmeter between alternator terminal
"S" and ground. See Fig. 10. Connect positive voltmeter lead to
terminal "S" of alternator. Connect negative voltmeter lead to ground.
2) Disconnect alternator output wire from terminal "B".
Install a 100-amp ammeter in series to terminal "B" and disconnected
output lead. Install positive lead of ammeter to terminal "B" and
negative lead to disconnected output wire. Install a tachometer, and
reconnect negative battery cable.
3) Turn ignition switch to ON position and ensure voltmeter
indicates battery voltage. If no voltage exists, an open circuit

exists in wire between alternator terminal "S" and positive battery
terminal or fusible link is blown.
4) Start engine. Ensure all lights and accessories are off.
Operate engine at 2500 RPM and read voltmeter when alternator output
current drops to 10 amps or less. Voltage regulator is okay if voltage
output is within specification. See REGULATOR VOLTAGE SPECIFICATIONS
table.
BENCH TESTING
RECTIFIER ASSEMBLY
1) Using ohmmeter, check for continuity between both diodes
and stator coil lead connection. See Fig. 11. Reverse leads. If
continuity exists in both directions, diode is shorted. Replace
rectifier assembly.
2) To check entire diode assembly, use an ohmmeter to check
for continuity between both ends of each diode. See Fig. 11. Switch
ohmmeter leads. Continuity should exist in one direction, but not
other. If no continuity exists or continuity exists in both
directions, diode is defective. Replace rectifier assembly.
Fig. 11: Testing Rectifier Assembly
Courtesy of Mitsubishi Motor Sales of America.
ROTOR

BRAK E S YSTE M

1991 M it s u bis h i M onte ro
1991 BRAKES
Disc & Drum
Chrysler Motors: Ram-50;
Mitsubishi: Montero, Pickup
DESCRIPTION
Brake system consists of a master cylinder, vacuum power
brake unit, proportioning valve and self-adjusting assembly. Pickup
and Ram-50 models have a Load-Sensing Proportioning Valve (LSPV). All
models are equipped with front disc brakes and rear drum brakes.
Parking brake assembly activates rear brakes.
BLEEDING BRAKE SYSTEM
BLEEDING PROCEDURES
Montero
Bleed brake system in following order: right rear, right
front and left front (one circuit handles both rear brakes).
Pickup & Ram-50
Bleed brake system in following order: right rear, left rear,
LSPV, right front and left front.
ADJUSTMENTS
BRAKE PEDAL HEIGHT & FREE PLAY
1) Separate connector from stoplight switch, and loosen lock
nut. Position switch so it does not contact brake pedal arm. Adjust
brake pedal height by rotating master cylinder push rod (yoke, if
equipped) until distance from top of brake pedal to floor board is
correct. See BRAKE PEDAL SPECIFICATIONS table.
2) DO NOT depress push rod. Tighten lock nut, and ensure
brake pedal height is within specification. Start engine to evacuate
brake booster chamber. Stop engine, and apply brake several times to
remove vacuum from brake booster.
3) Using hand pressure, depress brake pedal to measure free
play before resistance is felt. If distance is incorrect, bleed the
brake hydraulic system, and check for misadjusted brakes. Refer to the
BRAKE PEDAL SPECIFICATIONS table.
BRAKE PEDAL SPECIFICATIONS TABLE









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Free Play Pedal Height
Application In. (mm) In. (mm)
Montero ............ .12-.31 (3-8) ... 7.5-7.7 (191-196)
Pickup & Ram-50 .... .12-.31 (3-8) ........... 6.5 (166)









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LOAD-SENSING PROPORTIONING VALVE (LSPV) (Pickup & Ram-50)
Park vehicle on level surface. Remove all luggage and
passengers. Ensure lever is not against stopper bolt. Check spring

brake pedal to center shoes, and check pedal travel. Rotate brake drum
to verify free movement.
STOPLIGHT SWITCH
Loosen lock nut, and adjust switch-to-pedal arm clearance to
.02-.04" (.5-1.0 mm). Tighten lock nut. DO NOT depress master cylinder
push rod during stoplight switch adjustment.
TESTING
POWER BRAKE UNIT
Check Valve Inspection
Remove vacuum hose from power brake unit. Remove check valve
from hose (if possible). Using a vacuum pump, ensure airflow is in
direction of intake manifold only.
System Check
1) Run engine for 2 minutes, and shut it off. Depress brake
pedal several times with normal pressure. If pedal height gradually
becomes higher with successive applications, power brake unit is okay.
If pedal height remains steady, power brake unit is faulty.
2) With engine stopped, depress brake pedal repeatedly until
it's height no longer falls. Hold brake pedal down, and start engine.
If pedal moves downward slightly, power brake unit is okay. If pedal
height does not change, power brake unit is faulty.
3) With engine running, press and hold brake pedal and shut
off engine. Hold brake pedal for 30 seconds. Brake pedal height should
not change. If pedal height falls, power brake unit is faulty.
LOAD-SENSING PROPORTIONING VALVE (LSPV) (PICKUP & RAM-50)
1) Before diagnosing Load-Sensing Proportioning Valve (LSPV)\
,
ensure all other brake components are operating properly. When all
other brake system components are determined to be okay, perform LSPV
test beginning with next step.
2) Ensure unladen vehicle is on level ground. Ensure lever is
not contacting stopper bolt. See Fig. 1.
3) When lever is pushed toward valve, distance from LSPV
lever hole and support hole must be 6.97-7.09 in. (177-180 mm). If
measured distance is not within specification, loosen support bolt.
Adjust support until measured distance is within specification.
4) After measured distance is within specification, connect
pressure gauges to input and output ports of LSPV. See Fig. 4. Bleed
brake system. See BLEEDING BRAKE SYSTEM .
Fig. 4: Connecting Pressure Gauges to LSPV (Pickup & Ram-50)
Courtesy of Mitsubishi Motor Sales of America.

Colt, Colt 200, Mirage & Summit
Remove defogger timer from junction block under left side of
instrument panel. Connect a battery and test light to defogger timer
terminals. See Fig. 3. Apply battery voltage to terminal No. 7 for 5-7
seconds. Ensure test light illuminates for approximately 10 seconds.
Reapply battery voltage to terminal No. 7. Test light should go off
when voltage is applied again.
Colt Vista
With ignition switch in ON position, apply battery voltage to
terminal No. 2 of defogger timer. Timer should operate for
approximately 11 seconds then stop. See Fig. 3.
Eclipse & Galant
Remove defogger timer from interior relay block. Connect
battery voltage and test light to timer. See Fig. 3. Ensure test light
illuminates for approximately 11 seconds when battery voltage is
applied to terminal No. 4. Reapply battery voltage to terminal No. 4
and observe test light. Test light should go off.
Fig. 3: Identifying Defogger Timer Terminals
Courtesy of Chrysler Motors.
GRID TEST
1) Start engine and operate at 2000 RPM. Ensure battery is
fully charged. Turn defogger switch to ON position. Using a voltmeter,
check voltage at center section of each grid wire. If voltage is
approximately 6 volts, grid wire is okay. If voltage is approximately
12 volts, an open is present in the negative circuit. Move probe
slowly toward the negative terminal to determine location of open
circuit.
2) If voltage is zero volt, an open is present in the
positive circuit. Move probe slowly toward the positive terminal to

Abbreviation Description
AIS ............................ Air Injection System
CBVV ..................... Carburetor Bowl Vent Valve
CE ............................... Check Engine Light
CEC ..................... Computerized Engine Control
EGR ....................... Exhaust Gas Recirculation
EGR-CS ......................... EGR Control Solenoid
EGR-TS ....................... EGR Temperature Sensor
EGR-TV .............................. EGR Thermovalve
EGR-TVS ................... EGR Thermal Vacuum Switch
EGR-VRV .................. EGR Vacuum Regulator Valve
EVAP ........................ Fuel Evaporation System
EVAP-CBVV ........... EVAP Carburetor Bowl Vent Valve
EVAP-CS ....................... EVAP Control Solenoid
EVAP-PV ............................ EVAP Purge Valve
EVAP-TV .......................... EVAP Thermal Valve
EVAP-VC ......................... EVAP Vapor Canister
FBC ............................. Feedback Carburetor
HAC ...................... High Altitude Compensation
HAC-VSV .................. HAC Vacuum Switching Valve
MCV ........................... Mixture Control Valve
O2 .................................... Oxygen Sensor
PAS ............................. Pulse Air Injection
PAS-PAV ......................... PAS Pulse Air Valve
PAS-PAVCS ............ PAS Air Valve Control Solenoid
PAV ................................. Pulse Air Valve
PAV-CSOLV ................ PAV Control Solenoid Valve
PCV .................. Positive Crankcase Ventilation
PFI ............................. Port Fuel Injection
PG-CSOLV ............... Purge Control Solenoid Valve
PG-CV .......................... Purge Control Valve
PG-TV ............................. Purge Thermovalve
SPK ................................... Spark Control
SPK-CC ...................... SPK Computer Controlled
SPK-TVS ................... SPK Thermal Vacuum Switch
TAC ........................ Thermostatic Air Cleaner
TWC .............................. Three-Way Catalyst









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