Ford Workshop Service and Repair Manuals

General

Description

A Siemens Common Rail diesel fuel injection system is introduced in the 1.4L DuraTorq TDCi turbodiesel engine.

Common rail diesel fuel injection systems are pressure storage injection systems. This means that the fuel pressure is continuously available on these systems, whereas on traditional systems with distributor injection pumps, the pressure must be newly built up for every injection.

Creation of pressure and fuel injection are performed separately on common rail diesel fuel injection systems. Because of this, the build up of injection pressure is largely independent of engine speed and injection quantity.

An injection pressure of up to 1,500 bar is kept ready in the fuel distribution rail (common rail).

General operation

An integral transfer pump is found inside the high pressure pump, and this transfers the fuel from the tank to the high pressure pump.

The high pressure pump supplies fuel through the high pressure system into the common rail and to the injectors and builds up the injection pressure there.

Injection timing and quantity are calculated by the powertrain control module ( PCM) .

Using various input variables, the PCM controls the piezoelectrically operated injectors, which inject the required quantity of fuel into the applicable combustion chamber.

The fuel pressure sensor on the common rail provides the PCM with information on the current fuel pressure. Another variable is the fuel temperature.

Based on these input variables, the PCM controls the fuel metering for the system by using the fuel metering valve and the fuel pressure regulator, so that the optimum fuel pressure is available for every operating state.

Excess fuel passes through the fuel return collector pipe, past the fuel temperature sensor, and back to the fuel tank.

In the tank a venturi pump ensures that the fuel returned helps the filling of the fuel supply unit in the tank.

High-pressure pump

Fuel supply is carried out through an integral transfer pump. This is a vane cell pump and is driven by the drive shaft of the high pressure pump.

The fuel passes from the transfer pump to the high pressure pump itself. This is contains three pump cylinders which are arranged radially.

The fuel metering valve is located in the supply channel between the transfer pump and the high pressure pump. The fuel metering valve operates electromagnetically and is controlled by the PCM .

The fuel metering valve affects the fuel flow to the high pressure pump, and thus controls the amount of fuel destined for the high pressure pump.

The fuel pressure regulator controls the output pressure of the high pressure pump. The fuel pressure regulator operates electromagnetically and is controlled by the PCM .

Operation of the high pressure pump

The storage pressure required for the common rail is created in the high pressure pump.

Three pump cylinders are arranged radially around the drive shaft.

Fuel is sucked into the inside of the pump cylinders by the rotating motion of the drive shaft, and is supplied under pressure to the common rail and also to the high pressure system.

Fuel flow through the high pressure pump during acceleration

During acceleration fuel is passed unrestricted from the transfer pump through the supply channel to the high pressure pump.

A proportion of the fuel passes through a calibrated return bore, past the fuel temperature sensor and back to the tank, thus serving to cool and lubricate the pump.

Fuel flow through the high pressure pump during over-run.

In over-run, the fuel metering valve closes the supply channel from the transfer pump to the high pressure pump. This causes the pressure in the supply channel to increase.

When a given pressure is reached, a pressure control valve opens, which is connected by a bore to the transfer pump.

The excess fuel partly flows back to the suction side of the transfer pump, partly back into the tank.

Common rail

The fuel supplied by the high pressure pump passes through a high pressure line into the common rail.

The common rail is made of forged steel. It stores fuel under high pressure and damps pressure fluctuations.

The fuel passes to the injectors through four high pressure lines.

Feedback information for pressure control is provided by a fuel pressure sensor located in the common rail.

NOTE:The fuel pressure sensor in the common rail must not be slackened or removed.

High pressure fuel lines

NOTE:The radii of the bends on the high pressure lines must not be changed.

NOTE:Every time the high pressure lines are undone, new ones must be installed, otherwise leaks can occur at the line unions because of the particularly high fuel pressure.

The high pressure fuel lines connect the common rail with the high pressure pump and the injectors.

The high pressure lines which lead to the injectors are all the same length. All the high pressure lines have bend radii which are matched to the system.

Injectors

CAUTION:Danger of damage to components. Never disconnect the wiring harness electrical connector from an injector with the engine running.

NOTE:New injectors must be installed if repairs are needed. They cannot be dismantled.

Start of injection and injection quantity are achieved by electrically controlled injectors.

Control of the injectors is performed directly by the PCM .

The injectors consist of three separate functional groups:

• Injector nozzle,
• hydraulic servo system,
• piezoelectric actuator.

Electromechanical operation is achieved using piezoelectric elements, which have a particularly fast switching time of approximately 0.2 milliseconds.

Low pressure fuel system

Fuel supply unit

The fuel supply unit contains an integral venturi pump. In this way, the returning fuel sucks up additional fuel into the housing. Because of this, the fuel volume of the tank is used in the most optimal way.

Fuel filter

The fuel filter is located on the air cleaner housing towards the transmission.

The fuel filter has electric fuel pre-heating for vehicle operation in low ambient temperatures.

The fuel filter forms a single component with the housing and can only be renewed as a complete unit.

In addition, the fuel filter is equipped with a water separator. This must be regularly drained in accordance with the service instructions.

To do this, the drain screw on the filter housing must be undone. Then allow approx. 80 ml of liquid to run out (collect and dispose of this) and then close the water drain screw again.

Low pressure fuel lines in the engine compartment

The low pressure fuel system is equipped with a manual pump. Using the manual pump, fuel can be supplied from the fuel tank through the fuel filter to just before the inlet to the high pressure pump, in order to allow the vane cell pump to suck fuel out of the tank itself.

The collector pipe for return fuel brings together the return lines from the high pressure pump, manual pump and leak off fuel and contains the fuel temperature sensor.