Non-turbo engines
The diesel engine fuel system includes a fuel tank, a high pressure fuel pump, a fuel filter mounted on the fuel pump and a main fuel filter, fuel supply and return lines, and fuel injectors installed one for each cylinder.
The fuel pump is driven by a chain and rotates at half the speed of the engine crankshaft. Fuel from the fuel tank is taken by the fuel pump through the primary and main filters and then supplied under high pressure to the fuel injectors.
The moment of fuel injection is set by turning the fuel pump on the mounting brackets. When the engine is running, the injection timing is determined mechanically by the fuel pump, depending on the position of the accelerator pedal and engine speed. The moment of fuel injection can be changed using the adjusting device located on the side of the fuel pump.
The fuel injector is a valve that opens at a strictly defined fuel pressure. The atomizer, located at the lower end of the nozzle, forms a torch of sprayed fuel of the required shape. The fuel is cut off by a needle under the influence of the nozzle spring. The atomizer and needle are a precision assembly and must be handled with care when repairing. Excess fuel after cut-off is pumped along the needle, lubricating it, and is discharged through the return pipeline to the fuel tank.
Serviceability and correct adjustment of injectors are very important for the normal operation of the engine. If the nozzle atomizer does not provide a torch of the required shape or a bad cut-off occurs, the engine starts to work with vibration, strong mechanical knocks appear, and pressure rises. It should be noted that nozzles from different engine models are externally the same, but have different characteristics, in particular, the shape of the torch, so new nozzles should be used only those that are designed for this model.
The engine is switched off using a vacuum switch, which is mounted on top of the high pressure fuel pump. When the key is turned in the ignition switch to position "OFF" a vacuum switch connected to the ignition switch closes the vacuum supply to the vacuum switch, which in turn cuts off the fuel supply to the fuel pump and the engine stops.
The idle speed of the engine is controlled by a mechanical regulator, which is built into the high pressure fuel pump. A centrifugal-type mechanical regulator changes the position of the fuel pump rack through a spring-loaded lever. Idle speed control is carried out by one or more actuators that change the idle speed when a load is applied. For example, when turning on the power steering, turning on the air conditioner, turning on the drive on models with an automatic transmission, or starting a cold engine.
On later models with 6-cylinder engines and models with 4- and 5-cylinder engines with an air conditioning system and an automatic transmission, an electronic idle control system is installed (ELR). In this system, an electronic control device monitors engine speed using a sensor mounted near the flywheel and coolant temperature using a sensor screwed into the cylinder head. The ECU compares the actual values with the values stored in the memory and, if necessary, turns on the electromagnetic actuator, which moves the fuel pump control and changes the engine idle speed.
On some models with a manual transmission, a system is installed that prevents engine jerks (ARA). This system, based on information about engine speed and coolant temperature, eliminates the possibility of car jerks during acceleration and deceleration. When approaching a jerk condition, an actuator mounted on the side of the fuel pump momentarily reduces the amount of fuel supplied. As a result, the engine torque is reduced and the tendency to jerk disappears. On models with 6-cylinder engines, the engine is controlled by an electronic device ELR, and on other models by a specialized electronic device.
Turbocharged engines
The operation of the fuel injection system on turbocharged engines is similar to the operation of the fuel injection system on non-turbocharged engines. On turbocharged engines, the idle speed control and anti-jerk control are controlled by the diesel engine's electronic control system (EDS), which also controls the pressure in the exhaust gas reburning system and the turbocharger.
When working on the fuel system, fuel may leak out, so care must be taken.
Attention! Do not allow diesel fuel to enter the cooling system hoses. Hoses that have been exposed to diesel fuel for a long time must be replaced.
Attention! The fuel system of a diesel engine is particularly sensitive to contamination, so be as clean as possible when working on the fuel system. Before disconnecting the fuel lines, thoroughly clean them of dirt.
Attention! Do not use compressed air to clean engine-mounted fuel system components.
Attention! When checking the operation of the fuel injectors, never place your hands or any part of your body under the jet of fuel coming out of the injector. The fuel exits the nozzle at high pressure and can enter the body through the skin.