ISUZU 6SD1 Service Manual
For DENSO Authorized
ECD Service Dealer Only
Diesel Injection Pump
No. E-03-02
SERVICE MANUAL
Common Rail System for ISUZU
6HK1/6SD1 Type Engine
Operation
June, 2003
-1
00400018
GENERAL
The common rail system was designed for electronic control of injection quantity, injection timing and injection pressure to obtain optimal operational control.
Features
• Lower exhaust gas and higher output due to high pressure injection in all usage ranges.
• Reduction in noise and exhaust gas due to injection rate control.
• Improved performance due to increased flexibility in the injection timing setting.
• Independent control of injection pressure in response to engine speed and load.
Main Elements
Manufacturer Vehicle Model Engine Model
6HK1
ISUZU Forward
6SD1 9,800
6WG1 15,600
Cylinder
Configuration
Straight 6
Total
Displacement
(cc)
7,800
0
1. Outline
1.1 System Outline
This system also provides the following functions:
• A self-diagnosis and alarm function using computer to diagnose the system’s major
components and alert the driver in the event of a problem.
• A fail-safe function to stop the engine, depending upon the location of the problem.
• A backup function to change the fuel regulation method, thus enabling the vehicle to
continue operation.
1.2 System Configuration
Divided by function, the system can be classified according to the fuel system and the control
system.
[1] Fuel System
High-pressure fuel that is generated by the supply pump is distributed to the cylinders using a
rail. Electromagnetic valves in the injectors then open and close the nozzle needle valve to control the start and end of fuel injection.
Electronic
control
Solenoid valve to control
the needle lift
Discharge
Fuel tank Supply pump Rail
volume
Injector
Q000080E
[2] Control System
Based on the signals received from various sensors mounted on the engine and the vehicle,
the ECU controls current timing and the duration in which the current is applied to the injectors,
thus ensuring an optimal amount of fuel is injected at an optimal time.
The control system can be broadly classified according to the following electronic components:
sensors, computers, and actuators.
Sensors Computers Actuators
Accelerator sensor
NE sensor
(Crankshaft position sensor)
TDC sensor
(Cylinder recognition sensor)
(Accelerator opening)
(Engine speed)
Cylinder
( )
recognition signal
ECU
Injectors
Fuel injection quantity
( )
and injection timing control etc.
Rail
Other sensors and switches
Supply pump
(Fuel pressure control)
1
Q000081E
[3] System Configuration (1)
Signals from
switches
ACCP
ECU
Charge-up
circuit
Accelerator position
sensor
Starter signal
Air cleaner
STA
THW
Water temp. sensor
THL
NE sensor
Fuel temp.
sensor
Leak pipe
Rail
Flow damper
Pressure limiter
Supply
pump
Fuel filiter
TDC sensor
Fuel tank
Q000082E
2
[4] System Configuration (2)
(inside Head Cover)
Injector
Injection Rate Control
Injection Quantity Control
Injection Timing Control
Injection Pressure Control
(Pressure Control in Rail)
Flow Damper
Rail Pressure sensor
Rail
Pressure Limiter
Crank Position
Sensor (NE Sensor)
Supply Pump
Cylinder Recognition
Sensor (TDC Sensor)
Accelerator Position
Sensor
Coolant Temperature Sensor
Atmospheric Air Temperature Sensor
·
·Fuel Temperature Sensor
·
Boost Pressure Sensor
ECU
Fuel
Injection
·Injection Quantity Control
·Injection Pressure Control
·Injection Timimg Control
Vehicle
Engine
Atmospheric Air
·A/T Control
·Exhaust Break Control
·Engine Shut-down control
·TECHΤ COMMUNICATION
3
(inside ECU)
Pressure Sensor
Communication
(Scan Tool)
Service Tool
TECHΤ
(Dealer)
Q000083E
1.3 Construction and Operation of the System
The rail system is comprised of a supply pump, a rail, and injectors, and also includes an ECU
and sensors to regulate those components.
The supply pump generates the internal fuel pressure in the rail. Fuel pressure is regulated by
the quantity of fuel discharged by the supply pump. In turn, the fuel discharge quantity is regulated by electronic signals from the ECU that turn the PCVs (pump control valves) ON and OFF.
Upon receiving fuel pressurized by the supply pump, the rail distributes the fuel to the cylinders.
The pressurized fuel is detected by the rail pressure sensor (installed in the rail) and undergoes
feedback control so that actual pressure will match the command pressure (designated according to the engine speed and load).
Pressurized fuel in the rail passes through the injection pipes that lead to the cylinders, and applies
pressure to the injector nozzles and the control chamber.
The injector regulates injection quantity and timing by turning the TWV (two-way valve) ON and OFF.
When the TWV is ON (current applied), the fuel circuit switches over, causing the high-pressure
fuel in the control chamber to flow out via the orifice. As a result, the force of the high-pressure
fuel at the nozzle valve opening causes the needle valve to lift, thus starting the injection of fuel.
When the TWV is turned OFF (current not applied), the fuel circuit switches over so that highpressure fuel, traveling via the orifice, is introduced to the control chamber. As a result, the needle valve lowers, thus ending the injection of fuel.
Thus, through electronic control, the timing of the current applied to the TWV determines the
injection timing, and the duration in which current is applied to the TWV determines the injection
quantity.
Additional information
(temperature, pressure)
Engine load
ECU
TWV control pulse
Rail pressure sensor
Supply Pump
Rail
Injection
pressure
control
Injector
TWV
· Injection quantity control
· Injection timing control
· Injection rate control
Leak
Orifice
Control chamber
Hydraulic piston
Nozzle
Needle
Q000084E
4
1.4 Comparison to Conventional Pump
Inline Type Common Rail System
System
Injection quantity
regulation
Injection timing
regulation
Distribution of
generated pressure
Distribution
Injection pressure
regulation
Pipe
Instantaneous high
pressure
Timer
Governor
Pump
Pump (governor)
Pump (timer)
Pump
Pump
(Dependent on engine speed and injection volume)
Nozzle
Rail
Constant high
pressure
Supply pump
Injector
ECU, injector (TWV)
ECU, injector (TWV)
Supply pump
Rail
Supply pump (PCV)
Q000085E
5
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