- accurate dosing of the amount of fuel in any operating condition of the engine with lower fuel consumption and good running performance;
- reduction of toxicity of the fulfilled gases as a result of precisely measured fuel;
- the possibility of purifying exhaust gases with a lambda-controlled catalyst;
- self-diagnosis of the injection control unit, as a result of which - a quick finding of a malfunction;
- The injection system is equipped with a memory in which malfunctions are recorded.
If malfunctions occur in the injection system or the engine during operation, they are stored in the memory. Faults recorded can be printed out using the VW memory interrogator. If the injection system or engine is not working properly, the CTO-VW can print out a list of faults for further troubleshooting.
Attention! If the battery is disconnected, the fault memory is cleared. If the fault reappears while driving, it is recorded.
The injection system consists of virtually no wear parts and requires virtually no maintenance, only the air filter element needs to be replaced every 30,000 km.
Significant repair and adjustment work can only be carried out with the help of expensive VW control units, so such work can only be carried out by suitably equipped workshops.
Attention! When working on the injection system, the same rules of cleanliness must be observed as when working on the ignition system.
Work in the injection system is hampered by a short hood cover, which limits access to the engine compartment. Based on this, the radiator with the grille and the fan simply lean forward. The tilting of the radiator is required for almost all work on the injection system and is described in subsection 2.2.
Digifant injection system
The Digifant system developed by VW AG In this system, the control of the ignition system and the injection system is integrated into the electronic control unit.
Fuel is taken from the fuel tank by an electric fuel pump and through the fuel filter on the bottom, is fed to the fuel distributor, then to the injection valves. The pressure regulator on the distribution pipe ensures that the fuel supply system maintains a constant pressure of about 2.5 bar. A vibration damper in the pressure regulator reduces pressure fluctuations in the fuel return line.
Air is drawn in by the engine through the air filter and enters the engine through the throttle valve and intake manifold. The position of the throttle valve is estimated by a potentiometer and serves as a measure for the control unit, together with the engine speed at the moment and the vacuum of the intake pipe, to regulate the air flow.
The control unit, depending on the amount of air supplied, regulates the injection time and the amount of injected fuel. The longer the injection valves are open, the more fuel is injected. Additional probes and sensors monitor the correct amount of fuel in special operating conditions.
The idle speed control valve regulates the idle speed, especially during the warm-up phase and if the engine is loaded with electrical appliances on.
The throttle valve potentiometer is located directly on the throttle shaft. It informs the control unit of the throttle position, especially idle and full power, due to which the traction switch is controlled. If the machine moves without using the engine force due to inertia, the control unit blocks the fuel supply to the engine. In this case, the throttle is in the idle position and the engine speed is slightly above 1500 rpm.
The pressure sensor is located in the control unit and is connected by a hose to the inlet pipe.
The Hall sensor in the ignition distributor informs the control unit about the number of revolutions at a given time.
The cold start valve additionally injects fuel into the intake manifold during a cold start. A faulty cold start valve makes it difficult to start the engine (cold and hot), degrades throttle response and increases fuel consumption.
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