The system consists of the fuel supply system, which includes the fuel tank, the fuel filter with a priming pump, the high-pressure pump, the injectors and the fuel lines.
The system also includes the air supply system, which consists of the air filter, the turbocharger, the charge-air cooler and the intake pipe.
Common Rail engine fuel system
A fuel pick-up with a coarse mesh filter is installed in the stamped steel tank.
The fuel tank is installed on the frame.
From the tank, fuel is supplied through the line via the fine filter to the high-pressure fuel pump (HP pump). From the pump, fuel under high pressure enters the rail, from where it is delivered to the injectors.
The fuel pick-up is secured to the tank by a clamping ring with screws through a rubber sealing ring.
The high-pressure pump delivers fuel to the common high-pressure line regardless of engine speed.
Fuel under high pressure accumulates in this line, from where it is constantly supplied to the injectors.
The ECM module regulates the fuel supply and injection timing by activating the injectors.
In this pump, the fuel pressure is raised to 250–1600 bar in three radial delivery chambers.
The actuator valve of the electronic fuel supply control system, installed at the inlet to these chambers, regulates the volume of fuel entering them.
To do this, it uses the signals from the ECM module, which maintains the pressure in the common high-pressure line at the required level.
Fuel that does not enter the delivery chambers exits through the cascade overflow valve.
This directs part of the fuel under pressure to the channels of the HP pump lubrication system and then ensures fuel return to the tank.
The fuel rail accumulates fuel and distributes it among the lines of the individual injectors.
A sensor is installed in the rail to monitor the pressure created in it by the high-pressure pump.
The signal from this sensor is used by the ECM module to regulate the delivery of the high-pressure fuel pump. In addition, there is a relief valve in the common line.
It acts as a safety valve, releasing excess pressure if the pressure in the fuel line exceeds the set level.
Fuel drained from the common high-pressure line is returned to the fuel tank through the return line.
The HP pump is driven by gears from the rear end of the crankshaft.
A mechanical priming pump is also installed in the pump housing to ensure fuel is drawn from the tank.
The fine fuel filter with a replaceable filter element, assembled with the priming fuel pump, is intended to clean the fuel in the engine fuel system from mechanical impurities and water.
It is located in the engine compartment on the left side on the frame side member.
The filter housing has an air bleed hole closed by a bolt, a mesh filter for pre-cleaning the fuel and a cock for draining sediment (water).
To prevent filter clogging in cold weather, an electric fuel heater is built into the filter housing.
The air filter is installed in the right-hand part of the engine compartment.
In the air filter, the air entering through the air intake is filtered by passing through the pleats of the filter element.
Then, through the union in the upper part of the filter housing, the air passes along the air duct to the engine turbocharger.
The air filter element has a large filtration area.
The filter element is made of porous cardboard.
The turbocharger is installed on the exhaust manifold and is intended to improve cylinder filling by utilising the energy of the exhaust gases.
The turbocharger consists of a single-stage compressor and a radial turbine.
The operating principle of the turbocharger is that the exhaust gases from the cylinders under pressure enter the gas turbine chamber through the exhaust manifold.
Expanding, the gases rotate the turbine wheel.
The rotation is transmitted through the shaft to the compressor wheel, which draws in air, compresses it and delivers it under pressure to the engine cylinders.
The turbine wheel is cast from a heat-resistant alloy and welded to the shaft.
The compressor wheel is cast from an aluminium alloy and secured to the shaft with a special nut.
The turbocharger shaft bearing is lubricated with oil supplied under pressure through the line from the oil pump.
From the turbocharger, the oil drains through the pipe into the engine crankcase.
The turbocharger has contact gas-oil seals with spring rings.
On the turbine side, the sealing rings are installed in the groove of the sleeve pressed onto the rotor shaft, and on the compressor side — in the groove of the compressor sleeve.
To increase the efficiency of the oil seal on the compressor side, the sealing ring area is separated from the area of active oil ejection from the bearing by an oil deflector forming an additional labyrinth.
The charge-air cooler (intercooler) is of tube-and-fin aluminium construction and is installed below the engine cooling system radiator.
Before entering the engine intake pipe, the air passes through the cooler, which is connected by air ducts to the turbocharger and the intake pipe.
To make engine starting easier, an electric heater «А» is built into the intake pipe.
When the ignition key is turned, the heater switches on and a lamp lights up on the instrument panel; once it goes out, the starter can be engaged.
The throttle body is a housing with a throttle valve controlled by an electric actuator from the electronic pedal signal.
The electronic throttle control pedal (accelerator pedal) is secured with bolts to the front panel.
Materials used and recommendations
When servicing the Common Rail fuel system, use only clean tools and cloths; the ingress of dirt into the fuel injection equipment is unacceptable. The fine fuel filter has a replaceable filter element, a built-in electric heater and a sediment drain cock; replace the filter element when it is dirty and drain the sediment through the cock.
The air filter has a filter element made of porous cardboard with a large filtration area; replace it when it is dirty. The turbocharger is lubricated with oil from the oil pump through the line, so monitor the tightness of the oil lines and the cleanliness of the air path. The charge-air cooler (intercooler) is connected by air ducts to the turbocharger and the intake pipe; check the tightness of the connections. The electric heater in the intake pipe switches on when the ignition key is turned; once the warning lamp goes out, the starter can be engaged. Observe the tightening torques and fire safety requirements when working with fuel.