Audi A4, S4

since 2000 of release

Repair and car operation

Power supply systems of petrol and diesel engines

General information and security measures

Petrol engines

Into structure of fuel system enter: fuel tank, fuel pump and fuel pipelines, and also fuel and air filters. Indications of rather fuel filter of the diesel engine are provided in Head the Current leaving and service.

The fuel tank has volume about 70 l and is located before a back suspension bracket of the car. The current volume of fuel in a tank is displayed to the driver on a control panel. The fuel tank has ventilation system. On the petrol engine of pair of gasoline gather in an adsorber and move in chambers of combustion of the engine.

The cable of an accelerator is absent. Instead of it on a pedal the sensor of its situation is established.

Essential influence on fuel consumption renders style of driving of the car. Some councils on the reasonable address with a gas pedal below are given.

After engine start at once get under way from a place even if it occurs on a frost. At a car stop for a while more than on 40 with, switch off the engine. Move always on the highest transfer. At movement on big distances whenever possible support uniform speed. Avoid movement on high speeds. Operate the car circumspectly. Without need do not brake. Do not transport on the car excessive cargo. If the luggage carrier is not used, remove it from a roof. Check pressure of air in tires. Do not allow excessive pressure decrease.

Diesel engines

At operation of the diesel engine in its cylinders clean air which is compressed to a high pressure is soaked up. Thus air in the cylinder heats up to the temperature exceeding temperature of ignition of diesel fuel. Fuel is injected into cylinders where air temperature makes near + 600 °C, with some advancing and ignites itself. Thus, spark plugs for ignition of fuel are not required.

There can be a situation when at very cold engine owing to compression the necessary temperature of ignition is not reached. In this case it is necessary to make preliminary heating of the engine. In each cylinder there is a glow plug which makes heating of the chamber of combustion. Duration of preheat depends on external temperature and is regulated by the control unit the engine via the preheat relay.

The diesel engine has three various ways of injection of fuel: by means of the vortical chamber, the prechamber and direct injection.

At vikhrekamerny and prechamber injection fuel is injected into the preliminary chamber of the corresponding cylinder. The mix ignites at once. The volume of oxygen which is available in the preliminary chamber is sufficient for combustion only parts of the injected fuel. The remained not burned down part of fuel the pressure, arisen in the course of combustion, jumps out the combustion chamber. There fuel burns down completely.

At direct injection fuel is injected directly into the combustion chamber.

Fuel moves the toplivopodkachivayushchy pump under the pressure of 3.5 atm. to the fuel pump of a high pressure (TNVD). In TNVD already at low numbers of turns constant pressure of compression over 1300 atm is created.

Into structure of fuel system enter: a fuel tank, the fuel filter, nozzles, fuel tubes and hoses, the sensor of a stock of the fuel, located in a tank and the block of electronic control by the engine.

Fuel moves the special pump via the filter. In the filter dirt and the water containing in fuel settles.

The engine copes the electronic system similar to a control system of petrol engines. The system operates operation of the engine, analyzing information arriving from a large number of sensors.

The valve of an otsechka of fuel at switching off of ignition is absent. To muffle the engine at ignition switching off, the control unit the engine sends a signal which, in turn, stops supply of fuel to nozzles to the TNVD control unit.

The fuel system is designed so that not to allow «подсоса» some air in the absence of fuel in a tank. The control unit constantly checks fuel level in a tank, processing information arriving from the sensor of a stock of fuel, located in a tank. When falling a stock of fuel to a certain level the control unit lights warning lamp on a control panel then compulsorily causes admissions of supply of fuel, limiting to that the maximum speed. It proceeds until fuel level in a tank will not exceed an admissible mark.

The fuel system of diesel engines is very reliable. During the using of pure fuel and performance of regular service it should function regularly before the termination of service life of the car. After very big run internal components of nozzles can wear out, and they will be necessary for repairing. As the pump - nozzles have a difficult design, repair is recommended to be carried out in a specialized workshop.

Security measures and rules of observance of purity at work with fuel system

Do not use near a workplace open fire, do not smoke and do not hold any strongly warmed up subjects. There is a danger of accident! Keep in readiness the fire extinguisher. Watch normal ventilation of a workplace. Fuel pairs are poisonous. The fuel system is under pressure. When opening system fuel can escape under pressure. Collect fuel a rag. Use goggles. At work with components of a power supply system of the diesel engine observe special precautionary measures. In special degree it belongs to nozzles. Keep in mind that pressure of fuel on an exit makes about 1100 atmospheres of nozzles. Do not allow hit of any parts of a body under a fuel stream. Shlangovye connections fasten by means of tape or tightening collars. It is necessary to replace tightening collars with tape collars or collars of the last design surely. For installation of tape collars there is a special adaptation, for example HAZET 796-5. Connections and places adjoining to them before opening carefully clear. The removed details stack on a pure lining and close. Apply for this purpose polyethylene or paper. Do not apply for this purpose a fibrous fabric! Carefully close open details or put technological caps if repair lasts some time. Establish into place only pure details. Spare parts take out from packing only directly ahead of installation. Do not apply details which were stored unpacked (for example, stored in a tool box). At the opened fuel system whenever possible do not work with the compressed air. Whenever possible do not move thus the car. Do not apply hermetics containing silicone. The elements which have got to the engine of silicone in the engine do not burn down and damage a lambda probe. Security measures at removal of a fuel tank Before removal of a tank merge from it fuel or pump out fuel pump specially provided for this purpose. The fuel tank acts in film from the bottom party of the car. Before a detachment of collars of fastening of a tank bring to it from below a jack and linings. The empty tank is explosive and cannot be utilized in such look. Before utilization the tank should be cut on a part. Watch that thus there was no spark. After tank installation into place start the engine and check tightness of all connections.