Valve injectors (Audi 80 B4)

Valve injectors are the final component of the fuel system of diesel engines. They are designed to inject fuel into the swirl chamber with its simultaneous atomization. Only when the required fuel pressure is provided does the injector needle rise and fuel is injected. The injection pressure on the injectors of cars produced before 6/92 is 155-163 bar, and for cars produced since 7/92 - 150-158 bar. The force of the spring pressing the injector needle is so great that the pressure generated during combustion of the air-fuel mixture cannot penetrate the fuel system. And if this happens, for example, due to sticking of the needle, then the corresponding injector can be distinguished by a strong knock (see illustration 3.0a).



Starting from 7/92, AUDI 80 cars are equipped with two-stage injectors, which are distinguished by an enlarged body. Their recognition by the article number is more reliable. Injectors intended for installation on cars manufactured before 6/92 have the number 068 130 202 E, and for cars manufactured after 7/92 - 028 130 201 B (see illustration 3.0b).



Cooling and lubrication of the injector needle is provided by diesel fuel. Since not all the fuel is injected into the combustion chambers of the cylinders, the remaining part is diverted back to the fuel tank (see illustration 3.0v).





The nominal value of the time interval from the start of fuel injection to the ignition of the mixture is 0.002 seconds. The slightest deviation, caused by various reasons, including poor mixture formation, uneven fuel supply, leads to a decrease in the effective engine power and/or the appearance of so-called detonation knocks.

Diesel engines, which are equipped with AUDI 80 cars, do not exhibit detonation knocks during normal operation. They can be felt only when starting a cold engine.

However, if detonation knocks are heard when the engine is warm, then the reason for this is a delay in the ignition of the mixture, i.e. the time interval between the start of injection and the ignition of the mixture is too large.

The reasons for such engine behavior may be:

• injector needle sticking;
• waxing of fuel, for example when using summer type in cold weather;
• too high load at low revs;
• too low compression.

A faulty injector can be identified with the engine running by loosening the union nut of the fuel supply line of each injector in order. If, when loosening the union nut of the fuel line of the corresponding injector, the idle speed does not change and remains constant, then this injector is faulty.



A defective injector may manifest itself in the following:

• constant failure of the glow plug. The time interval between forced replacement of the plugs is very short.
• black exhaust.
• high fuel consumption.
• engine overheating.
• loud knocks.
• loss of engine power.
• uneven engine running.

[The original article is located on the online resource: AUDImanual.ru]