The high pressure injection system is designed to deliver a precise quantity of diesel fuel to the engine at a set
moment. The Siemens VDO piezo Common Rail system used on the K9K Step 2 engine is a second genera-
tion Common Rail injection system. Fuel pressure in the rail can reach a maximum of 1,600 bar. It uses fuel
injectors controlled by piezoelectric actuators. The fuel is pressurised by means of a high pressure pump then
sent to a rail which supplies the four fuel injectors.
• The circuit comprises two subsystems, which are distinguished by the fuel pressure level:
- the low pressure circuit comprises the tank, the diesel fuel filter, the transfer pump and the fuel injector return

lines,

- the high-pressure circuit comprises the high-pressure (HP) pump, the rail, the fuel injectors and the high-

pressure (HP) pipes.

Finally, there are a number of control sensors and actuators which enable the entire system to be controlled
and monitored.
• The system comprises:
- Priming bulb
- Fuel filter
- High pressure supply pump
- Fuel rail
- Fuel rail pressure sensor
- Fuel injector
- Fuel pump temperature sensor
- Engine coolant temperature sensor
- Camshaft position sensor
- Crankshaft position sensor
- Turbocharger boost sensor
- EGR volume control valve control position sensor
- EGR volume control valve
- Barometric pressure sensor (built in ECM)
- Mass air flow sensor
- Intake air temperature sensor
- Electric throttle control actuator

High Pressure Supply Pump

The high pressure supply pump consists of the following components:
• Internal fuel transfer pump:
- This pump is a vane-type rotary pump. It draws in fuel from the fuel tank through a fuel filter and supplies the

high pressure pump with fuel.

• Volumetric control valve:
- This solenoid valve regulates the flow of fuel entering the high pressure pump and enables an optimum

quantity of fuel to be pressurised according to operating phase; this improves the output of the high pressure
supply pump and thereby the output of the engine as well.

• High pressure pump:
- This pump is a 3-piston radial pump, it generates the required pressure in the rail.
• Pressure control valve:
- This solenoid valve regulates the output pressure of the high pressure pump.

Fuel Injector (Piezo Type)

CAUTION:

The fuel injector voltage is very high (much higher than that of conventional fuel injectors). This volt-
age can be as much as 150 V.
The piezo fuel injectors enable rapid, precise metering of the quantity of fuel injected, with excellent injection
process repetitivity.
The piezo actuator operates like a capacitor. To control the fuel injector, the computer sends, at the correct
time, a quantity of energy which is sufficient to enable the actuator to deform and the fuel injector to open.
During the injection period, the piezo actuator stores this energy.
At the end of the injection period, the computer recovers the energy sent at the start of the control operation.
The piezo actuator discharges and returns to its original shape. The fuel injector closes. To improve output, the

EC-1064

< FUNCTION DIAGNOSIS >

[K9K]

FUEL INJECTION CONTROL

energy returned by the piezo actuator is reused, which keeps down the amount of energy that has to be sup-
plied for the next injection process.

Engine Synchronisation

One of the determining factors for fuel injection control is knowing the position of each of the pistons in their
respective cylinders at all times.
The angular position is measured by means of a magneto-inductive sensor which is excited by the teeth
machined onto the flywheel; this is known as the crankshaft position sensor. The flywheel has 60 teeth, each 6
degrees apart; 2 of these teeth are missing to form a notch.
A second sensor (Hall-effect sensor), stimulated by a tooth machined onto the camshaft, which turns at half
the engine speed, provides a signal relating to the progress of the injection cycle. Indeed, when the piston of
cylinder 1 is at top dead centre (TDC), either at the end of the compression stroke or at the end of the exhaust
stroke, the camshaft position sensor enables a distinction to be made between these two states.
By comparing the signals from these two sensors, the computer is able to provide all its systems with synchro-
nisation parameters, namely: the angular position of the flywheel, engine speed, the number of the active fuel
injector and the progress of the injection cycle.
This module also supplies the system with the rotation speed signal.
The camshaft position sensor is only used when starting the engine. As soon as the engine is running by itself
(not being cranked by the starter), the signal provided by the crankshaft position sensor is sufficient. If the
camshaft position sensor should fail while the engine is running, this will not affect the operation of the engine.

Quantity of Fuel Injected and Control of Start of Injection

• The parameters for controlling injection are, for each cylinder, the quantity to be injected and the start of

injection. These are calculated by the ECM from the following information:

- Engine speed.
- Accelerator pedal position.
- Turbocharge air pressure.
- Engine coolant temperature.
- Intake air temperature.
- Fuel pump temperature.
- Mass air flow.
- Pressure of fuel in the rail.

Station to Station Flow Regulation

The aim of this regulation process is to facilitate smooth engine operation by compensating for the system
variations (fuel injectors, compression rate, etc.) which affect the torque generated by each cylinder during
combustion.
The regulation process is only active at idle speed, with a warm engine and on condition that the engine speed
is sufficiently stable. An injection timing correction coefficient is assigned to each cylinder; this is "learning" all
the time the regulation process is active and remains fixed at the last value that was learned when the regula-
tion is inactive.
At each new cycle, the coefficients are initialised to 1.

Cylinder Balancing Control

This controller allows smooth behavior of running engine, reduction of noise and oscillations in the drivetrain
by compensating for system dispersions (fuel injectors, compression ratio, manufacturing tolerances of cylin-
ders or valves...) having an influence on the torque generated by each cylinder during combustion.
The controller is only activated if engine is in idle, warm and not too rough. Corrective coefficient on the injec-
tion time is associated with each cylinder that is learnt as soon as the regulation is active. Otherwise it remains
with its last memorized value.
At each new driving cycle, coefficients are initialized to 1.

FUEL INJECTION CONTROL

EC-1065

< FUNCTION DIAGNOSIS >

[K9K]

Component Parts Location

INFOID:0000000001611144

Priming pump

Fuel pump

Glow plug

Fuel rail

Turbocharger boost control solenoid
valve

Turbocharger boost sensor

Engine coolant temperature sensor

Crankshaft position sensor

Glow relay

10. ECM

11.

Mass air flow sensor

12. Electric throttle control actuator

13. Camshaft position sensor

14. EGR volume control valve

15. Fuel injector

ALBIA0296ZZ

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