Audi A4, S4

since 2000 release

Repair and operation of the car

System of injection of fuel of the diesel engine

General information

The fuel system of the diesel engine copes an electronic control system of the engine. It has the following advantages:

• Self-diagnostics of a control system of the engine allows to run for fast troubleshooting.
• Exact dispensing of amount of injectable fuel provides reduction of the content of harmful substances in the fulfilled gases and low fuel consumption.
• Regulation of turns of idling and restriction of turns is made automatically.

During the operation of the diesel engine in its cylinders clean air which contracts to a high pressure is soaked up. Thus air temperature rises to 700 °C, the exceeding temperature of ignition of diesel fuel. Fuel is injected into the cylinder with some advancing and ignites. Thus, spark plugs for ignition of fuel are not used.

Air in the engine is sucked in or arrives from a turbocompressor and passes through the air filter. The turbocompressor compresses air which then arrives in an interkuler where it is cooled after heating as a result of compression in a turbocompressor. Cooling promotes the best filling of cylinders with the forced air that in turn raises a torque and engine capacity.

For reduction of a share of harmful substances in the fulfilled gases diesel engines have the diesel oxidizing catalytic converter. At the same time the system of recirculation provides essential decrease in the fulfilled gases of the content of oxides of nitrogen. It is reached thanks to supply of the fulfilled gases to the air which is soaked up by the engine that provides decrease in concentration of oxygen in the air coming to engine cylinders. It leads to a delay of ignition and to lower temperature of combustion that as a result reduces formation _{of NOx}. Process of recirculation of the fulfilled gases has to be dosed however precisely, otherwise the maintenance of a soot increases in the fulfilled gases. For this purpose the amount of the sucked-in air is defined by the measuring instrument that allows the electronic block to operate recirculation process.

Injection of fuel is carried out directly in the combustion chamber.

In the bottoms of pistons there are vortex chambers providing a turbulence of the fuel coming to combustion chambers.

Control of warming up of the cold engine is exercised the control unit of the engine. At the cold engine the moment of injection is displaced by the control unit. The control unit of the engine, in turn, operates work of candles of an incandescence. Glow plugs are installed in each cylinder and join before start of the engine, work during an engine provorachivaniye with a starter and some time after start of the engine. Candles considerably facilitate start of the cold engine. After inclusion of ignition on a control panel the lamp (address to the Head Governing bodies and methods of safe operation) signaling about inclusion of candles of an incandescence lights up. As soon as the lamp goes out, you can start the engine. If air temperature very low, candles continue to work still some time after start of the engine. It reaches stable operation of the engine and decrease in harmful impurity in the fulfilled gases.

Owing to high starting qualities of the engine with direct injection in a cold state preliminary heat is required only at a temperature below -10 °C.

Fuel passes through the fuel filter. In the filter fuel separates from water and pollution. Therefore it is important to delete water from fuel and to make timely replacement of the filtering element.

The engine of 2.5 l with direct injection

Fuel is soaked up by distributive TNVD from a fuel tank.

TNVD creates pressure about 900 atm. also injects fuel through multiple-jet nozzles in two steps, according to an ignition order. At first preliminary injection of small volume of fuel that creates necessary conditions for the subsequent injection of the main volume of fuel is made. Such process provides softer and less noisy combustion of fuel just as it occurs at vikhrekamerny injection.

TNVD does not demand service. All mobile parts of the pump are greased with diesel fuel. The TNVD drive is carried out from a cranked shaft of the engine by a gear belt.

The engine of 1.9 l with direct injection

Arrangement of elements of system of injection in a compartment of the diesel engine of 1.9 l

1 — the Mechanical valve of recirculation of the fulfilled gases with the gate of the inlet pipeline 2 — the Sensor of temperature of cooling liquid 3 — the block Socket the pump nozzle 4 — the fuel temperature Sensor 5 — the absorption pressure Sensor with the sensor of temperature of the soaked-up air 6 — the Socket of the sensor of number of turns of the engine 7 — the Socket of the sensor of the Hall of provision of a camshaft 8 — electronics Box in a water-collecting compartment. The control unit of system of direct injection with height sensor

9 — the Sensor of number of turns of the engine 10 — the Sensor of the Hall of provision of a camshaft 11 — the Electromagnetic valve of restriction of pressure of pressurization 12 — the Vacuum drive of pressure of restriction of pressure of pressurization 13 — the Valve of switching of the gate of the inlet pipeline 14 — the Valve of 1 system of recirculation of the fulfilled gases 15 — the Measuring instrument of mass of air

Here injection happens by means of pump nozzle system (an illustration lower). Unlike the previous system of injection where fuel compresses one TNVD for all nozzles, the pump nozzle system has own TNVD for each cylinder.

Thus, TNVD, the operating valve and a nozzle are integrated in one block.

Block pump nozzle

1 — the Nozzle 2 — pressure Pump 3 — the Control unit (the electromagnetic valve) 4 — the Roller lever 5 — an injection Cam 6 — the Cavity of a high pressure	7 — a piston Spring 8 — the pump Piston 9 — fuel Return 10 — fuel Supply 11 — the Glow plug 12 — a nozzle Needle

Supply of diesel fuel is carried out by the electric fuel pump located in a tank, and also the mechanical fuel pump giving fuel to the block the pump nozzle. Mechanical fuel to a nasosvmesta with the vacuum pump it is fixed on a head of cylinders and it is set in motion directly from a camshaft. Four fuel pumps of the block the pump nozzle are set in motion by an additional cam, located on distributive to a shaft, via the roller lever. The volume of injectable fuel is regulated by the engine control unit via electromagnetic valves.

Owing to a high pressure of compression in the block the pump nozzle fuel strongly heats up that has an adverse effect on operation of the sensor of a reserve of fuel in a tank. For cooling of fuel in the returnable pipeline there is a special refrigerator.

Before hit of fuel in the fuel pump it passes through the fuel filter. There from fuel water and pollution separate. It is necessary to pay attention to importance of service of the fuel filter.

During the work with fuel system it is necessary to observe security measures and special purity, address to the Section General information and security measures.