Isuzu 4JA1 Workshop Manual page 524

6E-270 Engine Control System (4JH1)
Fuel Injection System Description
Legend
1. Drive Shaft
2. Fuel Feed Pump
3. Pump Camshaft Position (CMP) Sensor
4. Fuel Injection Pump Control Unit (PCU)
5. Distributor Head
6. Constant Pressure Valve (CPV) Holder
Bosch VP44 Fuel Injection Pump
Instead of the previous face cam type, the radial
plunger distributor type injection pump utilizes a cam
ring to enable fuel injection at high-pressures, marking it
suitable for small, high-speed direct injection diesel
engines. This pump was developed to provide the most
suitable fuel injection quantity and injection timing to
satisfy the demand for engine reliability, driveability, low
smoke, low noise, high output and low exhaust
emissions.
The engine control module (ECM) calculates the
desired fuel injection quantity and timing using data sent
from various sensors. These desired data are sent to
the fuel injection pump control unit (PCU) via a
controller area network (CAN) communication bus. The
PCU also receives signals from the internal inputs:
pump camshaft position (CMP) sensor that is located
inside the fuel injection pump to determine the cam ring
7. Fuel Injection Solenoid Valve
8. Constran Pressure Valve (CPV)
9. Timing Control Valve (TCV)
10. Timer
11. Radial Plunger
rotation angle and the fuel injection pump speed. The
fuel temperature (FT) sensor is internal the PCU. These
values are used to compare the desired values sent
from the ECM then PCU determines the injection timer
piston position and fuel injection quantity, and actuates
timing control valve (TCV) & fuel injection solenoid
valve based on control maps in the PCU.
The timing device changes the optimum injection
timing against various engine conditions. The
pressure of the fuel fed from the feed pump is
adjusted and it acts to the timing plunger by TCV
controlled fuel pressure.
fuel injection pump rear side and it is controlled by duty
ratio cycle from the PCU.)
connected to the cam ring by a ball pin. Axial
movement of the timing plunger is transferred to the
cam ring in the form of rotational movement.
RTW66EMF000401
(The TCV is installed to the
The timing plunger is