Isuzu 4ja1, Workshop Manual

Page: 530 / 564

6E-276 Engine Control System (4JH1)
Timing Control Device Description
RTW66ESH003001
Legend
1. Cam Ring
2. Servo Valve
3. Timer Piston
4. Outlet
5. Feed
Pump
6. Inlet
7. Fuel
Suction
8. Ball Pin
9. Annular Chamber
10. Hydraulic Stopper
11. Return Passage
12. Timing Control Valve (TCV)
The timing device determines the optimum injection
timing against variations in engine speed. The pressure
of the fuel fed from the feed pump is adjusted in
accordance with speed by the regulating valve. This
delivery pressure acts on the hydraulic stopper's
annular chamber as control pressure. The chamber
pressure of the annular chamber is controlled by the
timing control valve (TCV). The timing plunger is
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. Movement to the right of
the timing plunger (to the spring side) advances
injection timing. The main components are timing
plunger, the TCV and pump camshaft position (CMP)
sensor.
Beginning of Injection Staring
RTW66ESH003101
The engine control module (ECM) contains
characteristic maps of the beginning of injection,
corresponding to engine operating conditions
(engine load, engine speed and engine coolant
temperature). The fuel injection pump control unit
(PCU) is constantly comparing the set beginning of
injection timing and the actual beginning of injection
timing. If there is a difference, the timing control
valve (TCV) is controlled by the duty ratio. (The
actual beginning of injection timing is determined
from the pump camshaft position [CMP] sensor.)
Timing Control Valve
RTW66ESH003201
Legend
1. Coil
2. From Annular Chamber
3. To Feed Pump
4. Orifice
5. Valve
Needle