Direct fuel injection (VW Golf 4)

With direct fuel injection, fuel is supplied directly into the combustion chamber. The fuel pump supplies fuel at a pressure of approximately 900 bar, and the fuel is injected in two stages.

The use of dual-channel fuel injectors allows for the initial injection of a small amount of fuel, resulting in improved combustion and a smoother combustion process. The amount of fuel injected is controlled by the electronic engine management system.

The amount of fuel injected is regulated by the control system based on information from the following sensors:

• accelerator pedal position sensor. The accelerator pedal position sensor provides information to the engine control unit about the current position of the accelerator pedal;
• engine crankshaft speed sensor;
• fuel injector needle displacement sensor. Based on the information from this sensor, the fuel injection moment is determined and the injection process is adjusted depending on the operating conditions and engine crankshaft speed;
• engine Air Intake Pressure Sensor (boost sensor);
• engine Air Temperature Sensor;
• coolant temperature sensor;
• diesel fuel temperature sensor;
• spool position potentiometer. Based on the information from this sensor, the actual amount of fuel injected is determined.

The air entering the engine in the intake ports is twisted in a spiral, which improves the combustion process in the engine cylinders. This also makes it easier to start a cold engine, and engine preheating should be done at air temperatures below -10°C.

Before the fuel enters the high-pressure fuel pump, it passes through a fuel filter, where water is also separated from it and must be drained periodically.



The fuel pump is driven by the engine crankshaft via a toothed belt. The internal moving parts of the fuel pump are lubricated with diesel fuel.

Warning: Do not allow diesel fuel to come into contact with the cooling system hoses. Hoses that have been exposed to diesel fuel for a long time must be replaced.

Warning: The diesel engine fuel system is particularly sensitive to contamination, so when working on the fuel system, maintain maximum cleanliness. Before disconnecting the fuel lines, thoroughly clean them from dirt.

[The original article is posted on the website: www.vwmanual.ru]

Do not use compressed air to clean fuel system components mounted on the engine.

Warning: When checking the operation of the fuel injectors, never place your hands or any part of your body in the jet of fuel coming out of the injector. Fuel comes out of the injector under high pressure and can penetrate your skin.