1997 SSANGYONG KORANDO fuel pressure

1F2 -- 4 M161 ENGINE CONTROLS
D AEW OO M Y_2000
FASTENER TIGHTENING SPECIFICATIONS
ApplicationNSmLb-FtLb-In
Camshaft Position Sensor Retaining Bolts10--89
Canister Mounting Bolts6--53
Coolant Temperature Sensor3022--
Crankshaft Position Sensor Retaining Bolt10--89
Engine Control Module (ECM) Mounting Bracket Nuts10--89
Fuel Filter Mounting Bracket Bolt6--53
Fuel Filter Lines2821--
Fuel Pressure Test Connector2518--
Fuel Rail Assembly Bolts2518--
Fuel Return And Supply Lines2317--
Fuel Tank Retaining Nuts3828--
Knock Sensor Mounting Bolt2518--
Oxygen Sensor5541--
Pedal Position Censor Mounting Bolts And Nut6--53
Throttle Body Bolts12--106

1F2 -- 6 M161 ENGINE CONTROLS
D AEW OO M Y_2000
SPECIAL TOOLS AND EQUIPMENT
SPECIAL TOOLS TABLE
YAA1F890
661 589 00 46 00
Fuel Tank Cap Wrench
KAA1F490
103 589 00 21 00
Fuel Pressure Gauge

M161 ENGINE CONTROLS 1F2 -- 35
D AEW OO M Y_2000
KAB1F450
Failure
CodeDescriptionTrouble AreaMaintenance Hint
68Random / Multiple
Misfire
When detection misfire of
multiple cylinder for source of
over the emission threshold or
catalyst damage
DInspection the ignition system
DInspection the injection system
DInspection the fuel pressure
DInspection the compression pressure
DInspection the valve timing or
clearance
DInspection the air flow sensor
DInspection the crankshaft position
sensor and air gap
DInspection the engine wiring system
DInspection the Engine Control Module
(ECM)
Circuit Description
The ECM monitors the crankshaft and camshaft positions to detect if the engine is misfiring. The ECM looks for a quick
drop in crankshaft speed. Misfire multiple cylinder is monitored by engine roughness measuring. The actual roughness
value is compared with the actual (emission and catalyst damage) threshold.

1F2 -- 40 M161 ENGINE CONTROLS
D AEW OO M Y_2000
FUEL SYSTEM
The function of the fuel metering system is to deliver the correct amount of fuel to the engine under all operating condi-
tions. The fuel is delivered to the engine by the individual fuel injectors mounted into the intake manifold near each
cylinder.
The main fuel control sensors are the Mass Air Flow (MAF) sensor and the oxygen (O2) sensors.
The MAF sensor monitors the mass flow of the air being drawn into the engine. An electrically heated element is
mounted in the intake air stream, where it is cooled by the flow of incoming air. Engine Control Module (ECM) modu-
lates the flow of heating current to maintain the temperature differential between the heated film and the intake air at a
constant level. The amount of heating current required to maintain the temperature thus provides an index for the
mass air flow. This concept automatically compensates for variations in air density, as this is one of the factors that
determines the amount of warmth that the surrounding air absorbs from the heated element. MAF sensor is located
between the air filter and the throttle valve.
Under high fuel demands, the MAF sensor reads a high mass flow condition, such as wide open throttle. The ECM
uses this information to enrich the mixture, thus increasing the fuel injector on-- time, to provide the correct amount of
fuel. When decelerating, the mass flow decreases. This mass flow change is sensed by the MAF sensor and read by
the ECM, which then decreases the fuel injector on-- time due to the low fuel demand conditions.
The O2 sensors are located in the exhaust pipe before catalytic converter. The O2 sensors indicate to the ECM the
amount of oxygen in the exhaust gas, and the ECM changes the air/fuel ratio to the engine by controlling the fuel
injectors. The best air/fuel ratio to minimize exhaust emissions is 14.7 to 1, which allows the catalytic converter to
operate most efficiently. Because of the constant measuring and adjusting of the air/fuel ratio, the fuel injection system
is called a “closed loop” system.
The ECM uses voltage inputs from several sensors to determine how much fuel to provide to the engine. The fuel is
delivered under one of several conditions, called ‘‘modes”.
Starting Mode
When the ignition is turned ON, the ECM turns the fuel pump relay on for 1 second. The fuel pump then builds fuel
pressure. The ECM also checks the Engine Coolant Temperature (ECT) sensor and the Throttle Position (TP) sensor
and determines the proper air/fuel ratio for starting the engine. This ranges from 1.5 to 1 at -- 36°C(--33°F) coolant
temperature to 14.7 to 1 at 94°C (201°F) coolant temperature. The ECM controls the amount of fuel delivered in the
starting mode by changing how long the fuel injector is turned on and off. This is done by ‘‘pulsing” the fuel injectors for
very short times.
Run Mode
The run mode has two conditions called ‘‘open loop” and ‘‘closed loop”.
Open Loop
When the engine is first started and it is above 690 rpm, thesystem goes into “open loop” operation. In “open loop”, the
ECM ignores the signal from the HO2S and calculates the air/fuel ratio based on inputs from the ECT sensor and the
MAF sensor. The ECM stays in “open loop” until the following conditions are met:
DThe O2 has a varying voltage output, showing that it is hot enough to operate properly.
DThe ECT sensor is above a specified temperature (22.5°C).
DA specific amount of time has elapsed after starting the engine.
Closed Loop
The specific values for the above conditions vary with different engines and are stored in the Electronically Erasable
Programmable Read -- Only Memory (EEPROM). When these conditions are met, thesystem goes into “closed loop”
operation. In “closed loop”, the ECM calculates the air/fuel ratio (fuel injector on-- time) based on the signals from the
O2 sensors. This allows the air/fuel ratio to stay very close to 14.7 to 1.
Acceleration Mode
The ECM responds to rapid changes in throttle position and airflow and provides extra fuel.
Deceleration Mode
The ECM responds to changes in throttle position and airflow and reduces the amount of fuel. When deceleration is
very fast, the ECM can cut off fuel completely for short periods of time.

1F2 -- 42 M161 ENGINE CONTROLS
D AEW OO M Y_2000
FUEL PUMP
YAA1F380
Requirements for Fuel Pump
ItemSpecified ValueItemSpecified Value
System Pressure3.8 barMinimum Delivery at 8V30 Litre/Hr
Maximum Pressure8.5 bar (12 V)Operating Voltage8V
Minimum Pressure5.0 bar (12 V)Maximum Allowable
Current7.5 A
Nominal Voltage12 VAmbient Temperature-- 30 ~ +70°C
Minimum Amount
of Fuel Supply114 Liter/Hr (12 V, 3.8 bar,
-- 30 ~ +70°C)Maximum Amount
of Fuel Supply165 Liter/Hr (12V, 3.8 bar,
-- 3 0 ~ + 7 0°C)

1F2 -- 46 M161 ENGINE CONTROLS
D AEW OO M Y_2000
FUEL INJECTOR
YAA1F0C0
The Multipoint Fuel Injection (MFI) assembly is a solenoid -- operated device controlled by the Engine Control Module
(ECM) that meters pressurized fuel to an each individual cylinder. The injector sprays the fuel, in precise quantities at a
point in time determined by the ECM, directly toward the cylinder intake valve. ECM energizes the fuel injector solenoid
to lift the needle valve and to flow the fuel through the orifice. This injector ’s discharge orifice is calibrated to meet the
effective fuel atomization necessary for both ensuring the maximum homogeneity in the air -- fuel mixture and holding
the condensation along the walls of the intake tract to a minimum.
Fuel enters the top feed injector from above and flows through its vertical axis. The lower end extends into the intake
valve. Fuel from the tip is directed at the intake valve, causing it to become further atomized and vaporized before
entering the combustion chamber.
A fuel injector which is stuck partially open would cause a loss of fuel pressure after the engine is shut down. Also, an
extended crank time would be noticed on some engines. Dieseling could also occur because some fuel could be deliv-
ered to the engine after the ignition is turned off.

M161 ENGINE CONTROLS 1F2 -- 53
D AEW OO M Y_2000
Fuel Pressure Test
Tools Required
103 589 00 21 00 Fuel Pressure Gauge
1. Turn the ignition switch to “OFF” position.
2. Remove the fuel pressure test connector.
YAA1F700
3. Connect the fuel pressure gauge to the fuel pressure test connector.
4. Test the fuel pressure at idling by operating the engine using the fuel pressure gauge 103 589 00 21 00.
Vacuum Hose Connected (bar)
3.2~3.6
Vacuum Hose Disconnected (bar)3.7~4.2
5. Replace the pressure regulator diaphragm if out of the specification.
Internal Leakage Test
1. Connect the fuel pressure gauge 103 589 00 21 00 to
the fuel pressure test connector.
YAA1F0K0
2. Stop the engine for approximately 30 minutes and then check the fuel pressure changes.
Pressure change
Fuel pressure drops slowlyDFuel leakage at the injector
DFaulty fuel pressure regulator ’s diaphragm and O-ring
Fuel pressure drops rapidlyDFaulty check valve in the fuel pump
3. If there is no change in fuel pressure and maintain the following pressure over 30minutes, it is normal.
Fuel pressure (bar)
≥2.5

1F2 -- 54 M161 ENGINE CONTROLS
D AEW OO M Y_2000
FUEL PRESSURE REGULATOR
YA A 1 F0 F0
Function of the Fuel Pressure Regulator
The fuel pressure regulator maintains the fuel pressure
in the fuel line with the pressure of 3.2 bars to 3.8 bars
according to the intake manifold pressure. This operat-
ing pressure cannot be changed, and the fuel injection
volume will be only determined by the injection time.
Over supplied fuel returns to the fuel tank through the
return line.

There is no negative pressure applied to the spring
chamber (9) during the full load, and it is separated from
the fuel chamber (8) by the diaphragm (5).
When the fuel pressure goes up, the diaphragm forces
the compression spring (6) in the direction of compres-
sion . At this moment, the valve (3) sticks to the dia-
phragm by the fuel pressure, and the fuel return line (2)
opens. The fuel over supplied returns to the fuel tank
through the return line.
YAA1F490
2. Fuel return line
3. Valve
5. Diaphragm
6. Compression Spring
8. Fuel Chamber
9. Spring Chamber
A. Valves Closed
B. Valves Opened