Isuzu KB P190. Manual - part 332

6E-294  Engine Control System (4JH1) 

Timing Control Device Description 

 

 
 

 

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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 

 

 
 
 

 

 

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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 

 

 

 

 

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 1. Coil 

  2.  From Annular Chamber 

  3.  To Feed Pump 

 4. Orifice 

 5. Valve 

Needle 

 

 

Engine Control System (4JH1)  6E-295 

The timing control valve (TCV) acts as a variable
throttle, using the rapid opening and closing (cycling)
of the valve needle in the TCV. At normal operation,
the TCV controls the pressure acting on the annular
chamber so that the hydraulic stopper cam move to
any position, from the retard position to the advance
position. At this time, the duty ratio is set by the fuel
injection pump control unit (PCU). 

 

When control current flows to the TCV coil, the valve
needle opens and the fuel annular chamber flows 
through the orifice to the feed pump inlet.
Consequently, the pressure of the annular chamber
decreases and the hydraulic stopper is moved to the 
retard side.

 

When control current to the TCV coil is cut, the valve
needle closes and the return passage is closed.
Consequently, the pressure of the annular chamber
increases and the hydraulic stopper is moved to the 
advance side. 

 
Pump Camshaft Position (CMP) Sensor  

 

 

 

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  1.  Pump Camshaft Position (CMP) Sensor  

  2.  Flexible Connecting Harness 

 3. Drive 

Shaft 

  4.  Pump Camshaft Position (CMP) Sensor Retaining

Ring  

 5. Sensor 

Wheel 

 

 

 

When the drive shaft rotates, the pump camshaft
position (CMP) sensor receives signal form the sensor 
wheel, and an electric pulse is sent through the flexible 
connecting harness to the fuel injection pump control 
unit (PCU). From these signals the PCU can determine 
the average pump speed and the momentary pump 
speed. The pump CMP sensor is mounted to the cam 
ring. Thus, the relationship between the cam ring and 
the pump CMP sensor signal is constant. The pump 
CMP sensor signal is utilized for the following purposes:

•  To determine the momentary angular position of 

the cam ring. 

•  To calculate the actual speed of the fuel injection 

pump. 

•  To determine the actual timing plunger position. 

 
 

 

 

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  1.  Pump Camshaft Position (CMP) Sensor Signal 

  2.  Crankshaft Position (CKP) Sensor Signal 

  3.  Fuel Injection Solenoid Valve Control Pulse 

  4.  Fuel Injection Solenoid Needle Valve Lift 

  5.  Cam Lift (Cam Profile) 

 6. Pulse 

Count 

  7.  Fuel Injection Solenoid Valve Close 

  8.  Fuel Injection Solenoid Valve Open 

  9.  Start of Pressure Delivery 

  10.  End of Pressure Delivery 

  11.  Pressure Delivery Angle 

 12.  Effective Stroke 

 

 

 
 
 

6E-296  Engine Control System (4JH1) 

•  Momentary Cam Ring Angular Position 
 

The momentary angular position of the cam ring is

input into the fuel injection PCU as a fuel injection

solenoid valve control signal. From momentary

input of angular position for fluctuations in running 

conditions, the fuel injection solenoid valve open

and close intervals corresponding to the cam ring's

cam lift can be accurately determined. 

•  Actual Injection Pump Speed 
  When the crankshaft position (CKP) sensor is 

faulty, the engine control module (ECM) uses the

pump CMP signal as a replacement signal. 

•  Actual Timing Plunger Position 
  The actual timing plunger position can be

determined by comparing the CKP sensor signal

with the pump CMP sensor angle. This position is

used for timer control. 

 

 

 

 

Engine Control System (4JH1)  6E-297 

Exhaust Gas Recirculation (EGR) System Description 

 

 
 
 

 

 

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Legend 

 1. EGR 

Cooler 

  2.  Engine Coolant Outlet 

  3.  Engine Coolant Inlet 

 4. EGR 

Valve 

 

 

 

 5. ECM 

  6.  MAF & IAT Sensor  

  7.  Intake Throttle Valve 

 

The EGR system recirculates a part of exhaust gas
back into the intake manifold, which results in reducing
nitrogen oxide (NOx) emissions. The EGR control
system uses an electronic control system solenoid valve
and vacuum control EGR valve to ensure both
driveability and low emission. The engine control
module (ECM) controls the EGR flow amount based on
the engine speed, engine coolant temperature, intake
air temperature, barometric pressure and fuel injection
quantity. The ECM controls the EGR valve opening by
controlling the EGR solenoid valve drive duty. The mass 

 

air flow (MAF) sensor monitors EGR gas flow amount.
An expected MAF amount should be detected while the
engine running.