low oil pressure ISUZU TROOPER 1998 Service Repair Manual

ABBREVIATIONS CHARTS
LIST OF AUTOMOTIVE ABBREVIATIONS WHICH MAY BE USED IN THIS MANUAL
A Ð Ampere(s)
ABS Ð Antilock Brake System
A/C Ð Air Conditioning
ACCEL Ð Accelerator
ACC Ð Accessary
Adj Ð Adjust
A/F Ð Air Fuel Ratio
AIR Ð Air Injection Reaction System
ALDL Ð Assembly Line Diagnostic Link
Alt Ð Altitude
AMP Ð Ampere(s)
ANT Ð Antenna
APS Ð Absolute Pressure Sensor
ASM Ð Assembly
A/T Ð Automatic Transmission/Transaxle
ATDC Ð After Top Dead Center
Auth Ð Authority
Auto Ð Automatic
BARO Ð Barometic
Bat Ð Battery
Bat+ Ð Battery Positive Terminal
Bbl Ð Barrel
BCM Ð Body Control Module
BHP Ð Brake Horsepower
BP Ð Back Pressure
BTDC Ð Before Top Dead Center
¡C ÐDegrees Celsius
Cat. Conv. Ð Catalytic Converter
cc Ð Cubic Centimeter
CCC Ð Computer Command Control
CCOT Ð Cycling Clutch Orifice Tube
CCP Ð Controlled Canister Purge
CID Ð Cubic Inch Displacement
CL Ð Closed Loop
CLCC Ð Closed Loop Carburetor Control
CO Ð Carbon Monoxide
Coax Ð Coaxial
Conn Ð Connector
Conv Ð Converter
CP Ð Canister Purge
CPS Ð Central Power Supply
Crank Ð Crankshaft
CTS Ð Coolant Temperature Sensor
Cu.In. Ð Cubic Inch
CV Ð Constant Velocity
Cyl Ð Cylinder(s)
C
3I Ð Computer Controlled Coil Ignition
DBM Ð Dual Bed Monolith
Diff Ð Differential
DIS Ð Direct Ignition System
Dist ÐDistributor
DOHC Ð Double Overhead Camshaft
DVM Ð Digital Voltmeter (10 meg.)
DVOM Ð Digital Volt Ohmmeter
DVDV Ð Differential Vacuum Delay Valve
EAC ÐElectric Air Control
EAS Ð Electric Air Switching
EBCM Ð Electronic Brake Control Module
ECC Ð Electronic Climate Control
ECM Ð Electronic Control Module
ECU Ð Electronic Control Unit
Ð Engine Calibration Unit (PROM)
EECS Ð Evaporative Emission Control System
EFE Ð Early Fuel Evaporation
EFI Ð Electronic Fuel Injection
EGR Ð Exhaust Gas Recirculation
EGR/TVS Ð Exhaust Gas Recirculation/Thermostatic
Vacuum Switch
ELC Ð Electronic Level Control
ESC Ð Electronic Spark Control
EST Ð Electronic Spark Control
ETR Ð Electronically Tuned Receiver
EVRV Ð Electronic Vacuum Regulator Valve (EGR)
Exh Ð Exhaust
¡F Ð Degrees Fahrenheit
FF Ð Front Drive Front Engine
FL Ð Fusible Link
FLW Ð Fusible Link Wire
FRT ÐFront
FWD Ð Front Wheel Drive
4WD Ð Four Wheel Drive
4x4 Ð Four Wheel Drive
4 A/T Ð Four Speed Automatic Transmission/Transaxle
Gal Ð Gallon
Gen Ð Generator
Gov Ð Governor
g Ð Gram
Harn Ð Harness
HC Ð Hydrocarbons
HD ÐHeavy Duty
HEI Ð High Energy Ignition
Hg Ð Mercury
HiAlt Ð High Altitude
HVAC Ð Heater-Vent-Air Conditioning
IAC Ð Idle Air Control
IC Ð Integrated Circuit
ID Ð Identification
Ð Inside Diameter
IDI Ð Integrated Direct Ignition
IGN Ð Ignition
ILC Ð Idle Load Compensator
INJ ÐInjection
IP Ð Instrument Panel
IPC Ð Instrument Panel Cluster
INT Ð Intake
J/B Ð Junction Block
km Ð Kilometers
km/h Ð Kilometer per Hour
kPa Ð KiloPascals
KV Ð Kilovolts (thousands of volts)
KW Ð Kilowatts
0AÐ12 GENERAL INFORMATION

00 Ð 50 SERVICE INFORMATION
Legend
1. Clutch Driver
2. Rotor Bearing Retainer
3. Pulley Rotor and Bearing
Assembly
4. Clutch Coil Assembly
5. Connector
6. Shaft Seal Parts
7. Pump Assembly
8. High Pressure Relief Valve
9. Shipping Cap
10. Special 134a Suction Port
11. Special 134a Discharge Port
Caution
The operations described below are based
on bench overhaul with the compressor
removed from the vehicle, except as noted.
They have been prepared in order of
accessibility of the components. When a
compressor is removed from the vehicle for
servicing, the amount of PAG lubricant
remaining in the compressor should be
drained, measured and recorded. This PAG
lubricant should then be discarded and an
equal amount of new PAG lubricant added to
the compressor.
The service compressor is shipped without
PAG oil. When service procedures require,
use only Isuzu approved PAG oil.
HEATING, VENTILATION AND AIR CONDITIONING(HVAC)
1
2
3
4
5
68
97
10
11
871RW002

1B Ð 4 AIR CONDITIONING
The refrigeration cycle includes the following four
processes as the refrigerant changes repeatedly
from liquid to gas and back to liquid while
circulating.
EVAPORATION
The refrigerant is changed from a liquid to a gas
inside the evaporator. The refrigerant mist that
enters the evaporator vaporizes readily. The liquid
refrigerant removes the required quantity of heat
(latent heat of vaporization) from the air around the
evaporator core cooling fins and rapidly vaporizes.
Removing the heat cools the air, which is then
radiated from the fins and lowers the temperature
of the air inside the vehicle.
The refrigerant liquid sent from the expansion valve
and the vaporized refrigerant gas are both present
inside the evaporator and the liquid is converted to
gas.
With this change from liquid to gas, the pressure
inside the evaporator must be kept low enough for
vaporization to occur at a lower temperature.
Because of that, the vaporized refrigerant is sucked
into the compressor.
COMPRESSION
The refrigerant is compressed by the compressor
until it is easily liquefied at normal temperature.
The vaporized refrigerant in the evaporator is
sucked into the compressor. This action maintains
the refrigerant inside the evaporator at a low
pressure so that it can easily vaporize, even at low
temperatures close to 0¡C (32¡F).
Also, the refrigerant sucked into the compressor is
compressed inside the cylinder to increase the
pressure and temperature to values such that the
refrigerant can easily liquefy at normal ambient
temperatures.
CONDENSATION
The refrigerant inside the condenser is cooled by
the outside air and changes from gas to liquid.
The high temperature, high pressure gas coming
from the compressor is cooled and liquefied by the
condenser with outside air and accumulated in the
receiver/drier. The heat radiated to the outside air
by the high temperature, high pressure gas in the
compressor is called heat of condensation. This is
the total quantity of heat (heat of vaporization) the
refrigerant removes from the vehicle interior via the
evaporator and the work (calculated as the quantity
of heat) performed for compression.
EXPANSION
The expansion valve lowers the pressure of the
refrigerant liquid so that it can easily vaporize.
The process of lowering the pressure to encourage
vaporization before the liquefied refrigerant is sent
to the evaporator is called expansion. In addition,
the expansion valve controls the flow rate of the
refrigerant liquid while decreasing the pressure.
That is, the quantity of refrigerant liquid vaporized
inside the evaporator is determined by the quantity
of heat which must be removed at a prescribed
vaporization temperature. It is important that the
quantity of refrigerant be controlled to exactly the
right value.
COMPRESSOR
The compressor performs two main functions:
It compresses low-pressure and low-temperature
refrigerant vapor from the evaporator into high-
pressure and high-temperature refrigerant vapor to
the condenser. And it pumps refrigerant and
refrigerant oil through the A/C system.
6VD1/6VE1 engine on RHD model is equipped with
an invariable capacity five-vane rotary compressor
(DKV-14D Type).
The compressor sucks and compresses refrigerant
by the rotation of the vane installed to the shaft,
and always discharges a fixed amount of refrigerant
independent of the load of refrigerant.
The thermo sensor is installed to the front head of
the compressor to protect it by stopping its
operation when the refrigerant gas is insufficient or
when the temperature is abnormally high.
·OFF ....... 160 ±5¡C (320.0 ±41¡F)
·ON ........ 135 ±5¡C (275.0 ±41¡F)
Diesel Engine models and 6VD1/6VE1 engine on
LHD model are equipped with a swash plate type
compressor
Swash plate compressors have a swash (slanted)
plate mounted on the shaft. When the shaft turns,
the rotation of the swash plate is converted to
reciprocating piston motion which sucks in and
compresses the refrigerant gas.
Shaft seal (Lip type) is installed between the valve
plate and shaft & cylinder head to prevent
refrigerant gas leaks. A specified amount of
compressor oil is contained in the oil pan.
This oil is supplied to the cylinders, bearings, etc.,
by an oil pump which is connected to the swash
plate shaft.

AIR CONDITIONING 1B Ð 5
With some compressors the differential between
the intake pressure and discharge pressure
generated while the compressor is operating is
used for lubrication instead of an oil pump.
The specified amount of the DKV-14D, DKS-15CH
and HD6 compressors oil is 150cc (4.2 Imp fl oz).
Also, compressor oil to be used varies according to
the compressor model. Be sure to avoid mixing
two or more different types of oil.
If the wrong oil is used, lubrication will be poor and
the compressor will seize or malfunction.
The magnetic clutch connector is a waterproof type.
MAGNETIC CLUTCH
The compressor is driven by the drive belt from the
crank pulley of the engine. If the compressor is
activated each time the engine is started, this
causes too much load to the engine. The magnetic
clutch transmits the power from the engine to the
compressor and activates it when the air
conditioning is ÒONÓ. Also, it cuts off the power
from the engine to the compressor when the air
conditioning is ÒOFFÓ. (Magnetic clutch repair
procedure can be found in Section 1D.)
CONDENSER
The condenser assembly in front of the radiator,
which carry the refrigerant and cooling fins to
provide rapid transfer of heat.
Also, it functions to cool and liquefy the high-
pressure and high-temperature vapor sent from the
compressor by the radiator fan or outside air.
A condenser may malfunction in two ways: it may
leak, or it may be restricted. A condenser restriction
will result in excessive compressor discharge
pressure. If a partial restriction is present, the
refrigerant expands after passing through the
restriction.
Thus, ice or frost may from immediately after the
restriction. If air flow through the condenser or
radiator is blocked, high discharge pressures will
result. During normal condenser operation, the
refrigerant outlet line will be slightly cooler than the
inlet line.
The vehicle is equipped with the condenser of the
parallel flow type condenser. A larger thermal
transmission area on the inner surface of the tube
allows the radiant heat to increase and the
ventilation resistance to decrease.
The refrigerant line connection has a bolt at the
block joint, for easy servicing.
RECEIVER/DRIER
The receiver/drier performs four functions;
·As the quantity of refrigerant circulated varies
depending on the refrigeration cycle conditions,
sufficient refrigerant is stored for the refrigera-
tion cycle to operate smoothly in accordance
with fluctuations in the quantity circulated.
·The liquefied refrigerant from the condenser is
mixed with refrigerant gas containing air
bubbles. If refrigerant containing air bubbles is
sent to the expansion valve, the cooling
capacity will decrease considerably. Therefore,
the liquid and air bubbles are separated and
only the liquid is sent to the expansion valve.
·The receiver/drier utilizes a filter and dryer to
remove the dirt and water mixed in the cycling
refrigerant.
·The sight glass, installed atop the receiver/
drier, show the state of the refrigerant.
A receiver/drier may fail due to a restriction inside
the body of the unit. A restriction at the inlet to the
receiver/drier will cause high pressures.
Outlet restrictions will be indicated by low pressure
and little or no cooling. An excessively cold
receiver/ drier outlet may indicate a restriction.
The receiver/drier of this vehicle is made of
aluminum with a smaller tank. It has 300 cc
(8.5 Imp fl oz) refrigerant capacity.
The refrigerant line connection has a bolt at the
block joint, for easy servicing.
DKV-14D TYPE
DKS-15CH TYPE
HD6 TYPE
Magnetic clutch
CompressorSuction side
Discharge side
Compressor Magnetic clutch
852RW031 871RY00012
871RY00011

AIR CONDITIONING 1B Ð 39
Removal Steps
1. Radiator grille
2. Pressure switch connector
3. Pressure switch
Installation Steps
To install, follow the removal steps in the
reverse order.
PRESSURE SWITCH
2
3
1
REMOVAL
Preparation:
·Disconnect the battery ground cable
·Discharge and recover refrigerant (Refer to
ÒREFRIGERANT RECOVERYÓ in this section.)
1. Radiator Grille
2. Pressure Switch Connector
3. Pressure Switch
When removing the switch connected part, the
connecting part should immediately be plugged or
capped to prevent foreign matter from being mixed
into the line.
INSTALLATION
To install, follow the removal steps in the reverse order,
noting the following points:
1. O-ring cannot be reused. Always replace with a new
one.
2. Be sure to apply new compressor oil to the O-ring
when connecting pressure switch.
3. Tighten the pressure switch to the specified torque.
Pressure Switch Torque Nám (kgám / lbáin)
13 (1.3 / 113)

1B Ð 40 AIR CONDITIONING
Legend
1. Pressure Switch Connector
2. Refrigerant Line
3. Receiver / Drier
4. Radiator Grille
5. Bracket Bolt
Receiver/Drier and Associated Parts (LHD V6 without Condenser Fan)
4
2
32 51
REMOVAL
1. Disconnect the battery ground cable
2. Discharge and recover refrigerant
·Refer to ÒREFRIGERANT RECOVERYÓ in this
section.
3. Remove radiator grille.
4. Disconnect pressure switch connector.
5. Disconnect refrigerant line.
·When removing the line connected part, the
connecting part should immediately be plugged or
capped to prevent foreign matter form being mixed
in to line.
6. Remove bracket bolt.
7. Remove receiver/drier.
·Loosen the bolt, then, using care not to touch or
bend the refrigerant line, carefully pull out the
receiver/drier.
INSTALLATION
To install, follow the removal steps in the reverse order,
noting the following points:
1. If installing a new receiver/drier, be sure to add
30cc(1.0 fl. oz.) of new compressor oil to a new one.
2. Put the receiver/drier in the bracket and connect with
the refrigerant line. Check that no excessive force is
imposed on the line. Fasten the bracket bolt to the
receiver/drier.
3. Tighten the refrigerant line to the specified torque.
Refrigerant Line Blot Torque Nám (kgám / lbáin)
6 (0.6 / 52)
4. O-rings cannot be reused. Always replace with new
ones.
5. Be sure to apply new compressor oil to the O-rings
when connecting the refrigerant line.
875RW002

AIR CONDITIONING 1B Ð 41
Pressure Switch and Associated Parts
2
3 1
Legend
1. Pressure switch connector
2. Pressure switch
3. Radiator Grille
REMOVAL
Preparation:
·Disconnect the battery ground cable
·Discharge and recover refrigerant (Refer to
ÒREFRIGERANT RECOVERYÓ in this section.)
1. Radiator Grille
2. Pressure Switch Connector
3. Pressure Switch
When removing the switch connected part, the
connecting part should immediately be plugged or
capped to prevent foreign matter from being mixed
into the line.
INSTALLATION
To install, follow the removal steps in the reverse order,
noting the following points:
1. O-ring cannot be reused. Always replace with a new
one.
2. Be sure to apply new compressor oil to the O-ring
when connecting pressure switch.
3. Tighten the pressure switch to the specified torque.
Pressure Switch Torque Nám (kgám / lbáin)
13 (1.3 / 113)
875RW005

1B Ð 50 AIR CONDITIONING
Removal Steps
1. Radiator grille
2. Air cleaner
2a. Dust
2b. Battery and reserver tank
2c. Air cleaner cover
3. Clip and clamp
4. Liquid line (High-pressure pipe)
5. Suction line (Low-pressure pipe)
6. Suction line (Low-pressure hose)
7. Discharge line (High-pressure hose)
Installation Steps
To install, follow the removal steps in the
reverse order.
REMOVAL
Preparation:
·Disconnect the battery ground cable
·Discharge and recover refrigerant (Refer to
ÒREFRIGERANT RECOVERYÓ in this section.)
1. Radiator Grille
2. Air Cleaner
2a. Duct
2b. Battery and Reserver Tank
2c. Air Cleaner Cover
3. Clip and Clamp
4. Liquid Line (High-pressure pipe)
5. Suction Line (Low-pressure pipe)
6. Suction Line (Low-pressure hose)
7. Discharge Line (High-pressure hose)
·Use a back-up wrench when disconnecting and
reconnecting the refrigerant lines.
·When removing the refrigerant line connecting
part, the connecting part should immediately be
plugged or capped to prevent foreign matter from
being mixed into the line.
INSTALLATION
To install, follow the removal steps in the reverse order,
noting the following points:
1. O-rings cannot be reused. Always replace new ones.
2. Be sure to apply compressor oil to the O-rings when
connecting refrigerant lines.
3. Tighten the refrigerant line to the specified torque.
(Refer to ÒSERVICE INFORMATIONÓ for FIXING
TORQUE in section 00.)

COMPRESSOR OVERHAUL 1D Ð 3
solvent, and dried with dry air. Use only lint free
cloths to wipe parts.
The operations described below are based on
bench overhaul with compressor removed from the
car, except as noted. They have been prepared in
order of accessibility of the components. When the
compressor is removed from the car for servicing,
the oil remaining in the compressor should be
discarded and new refrigerant oil added to the
compressor.
Magnetic clutch assembly repair procedures require
that the system be discharged of refrigerant. (Refer
to Section 1B for ÒREFRIGERANT RECOVERYÓ.)
Compressor malfunction will appear in one of four
ways: noise, seizure, leakage or low discharge
pressure. Resonant compressor noises are not
cause for alarm; however, irregular noise or rattles
may indicate broken parts or excessive clearances
due to wear. To check seizure, de-energize the
magnetic clutch and check to see if the drive plate
can be rotated. If rotation is impossible, the
compressor is seized. Low discharge pressure may
be due to a faulty internal seal of the compressor,
or a restriction in the compressor. Low discharge
pressure may also be due to an insufficient
refrigerant charge or a restriction elsewhere in the
system. These possibilities should be checked prior
to servicing the compressor. If the compressor is
inoperative, but is not seized, check to see if current
is being supplied to the magnetic clutch coil
terminals.
The compressor has vanes built into a rotor which
is mounted on a shaft.
When the shaft rotates, the vanes built into the
cylinder block assembly are opened by centrifugal
force.
This changes the volume of the space formed by
the rotor and cylinder, resulting in the intake and
compression of the refrigerant gas. The discharge
valve and the valve stopper, which protects the
discharge valve, are built into the cylinder block
assembly. There is no suction valve but a shaft seal
is installed between the shaft and head; a trigger
valve, which applies back pressure to the vanes, is
installed in the cylinder block and a refrigerant gas
temperature sensor is installed in the front head.
The specified quantity of compressor oil is
contained in the compressor to lubricate the various
parts using the refrigerant gas discharge pressure.
6VD1 engine is equipped with an invariable
capacity five-vane rotary compressor (DKV-14D
Type).
The compressor sucks and compresses refrigerant
by the rotation of the vane installed to the shaft,
and always discharges a fixed amount of refrigerant
independent of the load of refrigerant.The thermo sensor is installed to the front head of
the compressor to protect it by stopping its
operation when the refrigerant gas is insufficient or
when the temperature get abnormally high.
·OFF ..... 160 ±5¡C (320.0 ±9.0¡F)
·ON ..... 135 ±5¡C (275.0 ±9.0¡F)
4JG2 Engine are provided with a swash plate type
compressor (DKS-15CH Type)
Swash plate compressors have a swash (slanted)
plate mounted on the shaft. When the shaft turns,
the rotation of the swash plate is converted to
reciprocating piston motion which sucks in and
compresses the refrigerant gas.
Shaft seal (Lip type) is installed between the valve
plate and shaft & cylinder head to prevent
refrigerant gas leaks. A specified amount of
compressor oil is contained in the oil pan.
This oil is supplied to the cylinders, bearings, etc.,
by an oil pump which is connected to the swash
plate shaft.
With some compressors the differential between
the intake pressure and discharge pressure
generated while the compressor is operating is
used for lubrication instead of an oil pump.
Three pistons are arranged at 120g intervals around
the center of the swash plate shaft. These pistons
are connected to the ends of the swash plate
through shoe disks and balls.
The rotation of the swash plate causes
reciprocating movement of the piston inside the
cylinders, with each piston operating as two
cylinders. Because of that, the compressor operates
as though it has 6 cylinders.
The specified amount of the compressors oil is
150cc (4.2 Imp fl oz).
Also, compressor oil to be used varies according to
the compressor model. Be sure to avoid mixing two
or more different types of oil.
If the wrong oil is used, lubrication will be poor and
the compressor will seize or malfunction.

1D Ð 24 COMPRESSOR OVERHAUL
6. Remove any excess oil resulting from installing the
new seal parts from the shaft and inside the
compressor neck.
7. Install the clutch plate and hub assembly as
described previously.8. Reinstall compressor belt and tighten bracket.
9. Evacuate and charge the refrigerant system.
COMPRESSOR PRESSURE RELIEF VALVE
Removal
1. Recover the refrigerant using Refrigerant Recovery
System.
2. Remove old pressure relief valve.
Installation
1. Clean valve seat area on rear head.2. Lubricate O-ring of new pressure relief valve and
O-ring assembly with new 525 viscosity refrigerant
oil. Install new valve and torque in place, 9.0 Nám
(6.1 ft lbs)
3. Evacuate and recharge the system.
4. Leak test system.
COMPRESSOR OIL
Compressor Oil Check
The oil used to lubricate the compressor is circulating
with the refrigerant.
Whenever replacing any component of the system or a
large amount of gas leakage occurs, add oil to maintain
the original amount of oil.
Checking and Adjusting Oil Quantity for
Used Compressor
1. Perform oil return operation. Refer to Oil Return
Operation in this section.
2. Discharge and recover refrigerant and remove the
compressor.
3. Drain the compressor oil and measure the extracted
oil with a measuring cylinder.
4. If the amount of oil drained is much less than 90 cc
(3.0 fl. oz.), some refrigerant may have leaked out.
Conduct a leak tests on the connections of each
system, and if necessary, repair or replace faulty
parts.
5. Check the compressor oil contamination. (Refer to
Contamination of Compressor Oil in this section.)
6. Adjust the oil level following the next procedure
below.7. Install the compressor, then evacuate, charge and
perform the oil return operation.
8. Check system operation.
When it is impossible to preform oil return
operation, the compressor oil should be checked in
the following order:
1. Discharge and recover refrigerant and remove the
compressor.
2. Drain the compressor oil and measure the extracted
oil with a measuring cylinder.
3. Check the oil for contamination.
4. If more than 90 cc (3.0 fl. oz.) of oil is extracted from
the compressor, supply the same amount of oil to
the compressor to be installed. If the amount of oil
extracted is less than 90 cc (3.0 fl. oz.), recheck the
compressor oil in the following order:
5. Supply 90 cc (3.0 fl. oz.) of oil to the compressor
and install it onto the vehicle.
6. Evacuate and recharge with the proper amount of
refrigerant.
7. Perform the oil return operation.
8. Remove the compressor and recheck the amount of
oil.
9. Adjust the compressor oil, if necessary.
Checking and Adjusting for Compressor
Replacement
The oil is not charged in compressor (service parts). So
it is necessary to charge the proper amount of oil to the
new compressor. (Oil Capacity)
Capacity total in system 150 cc (5.0 fl.oz)
Compressor (Service 150 cc (5.0 fl.oz)
parts) charging amount
(Collected Amount) (Charging Amount)
more than 90 cc same as collected
(3.0 fl.oz) amount
less than 90 cc (3.0 fl.oz) 90 cc (3.0 fl.oz)
(Collected Amount) (Charging Amount)
more than 90 cc same as collected
(3.0 fl.oz) amount
less than 90 cc (3.0 fl.oz) 90 cc (3.0 fl.oz)