General information
Non-turbo engines
The main parts of the fuel system are a fuel tank, a high pressure fuel pump, a fuel pre-filter and a main fuel filter located in the engine compartment, fuel supply and return lines, as well as nozzles, one for each cylinder.
High pressure fuel pump (injection pump) has a chain drive from the camshaft and its rotation speed is equal to half the speed of rotation of the camshaft. Fuel from the fuel tank through the fuel pre-filter and the main fuel filter enters the high pressure fuel pump, which directs it at very high pressure through separate feed pipes to the injectors.
The main setting of the fuel timing is carried out by turning the high pressure fuel pump on the bracket supporting it. During engine operation, the timing of the start of fuel supply is controlled by the high pressure fuel pump itself and is primarily determined by the position of the accelerator and the engine speed. The injection timing can be changed using the threaded regulator located on the side of the injection pump.
The injectors are mechanical spring valves that open when the pressure of the incoming fuel exceeds a certain level. In this case, fuel from the nozzle of the nozzle is injected through the prechamber into the cylinder (indirect injection).
The engine is stopped by means of a vacuum-controlled cut-off valve, which is located on the lower wall of the injection pump. When the start key is set to "OFF", a vacuum switch integrated with the start key closes the vacuum line to the shut-off unit, which in turn cuts off fuel supply to the high pressure fuel pump, causing the engine to stop.
The operation of the engine in idle mode is controlled, first of all, by a mechanical regulator combined with a high-pressure fuel pump. The principle of operation of the regulator is based on the use of centrifugal force arising from the rotation of weights fixed on the pump axle, which through a spring-loaded lever change the position of the control rod of the high-pressure fuel pump. The governor mechanism can be actuated by one or more actuators, which makes it possible to gradually increase the engine speed in idling mode, taking into account the load, that is, when the power steering or air conditioning is operating, or when the automatic transmission drive is engaged, as well as under cold start conditions when mechanical friction is high.
Models with air conditioning and automatic transmission are equipped with an electronic idle control system (ELR). Using a sensor located on the flywheel and a sensor mounted in the cylinder head, this system monitors the engine speed and coolant temperature. The microprocessor compares the value of the engine speed with the optimal value stored in its memory. If these values differ, the microprocessor generates a control signal for an electromagnetic actuator, which mechanically acts on the regulator in order to change the idle speed accordingly.
Electronic Anti-Jerk System (ARA) usually installed on manual transmission models. This system uses information about engine speed and coolant temperature to minimize the vehicle's tendency to jerk when accelerating and decelerating a partially loaded vehicle. To do this, an electromagnetic drive mounted on the high pressure fuel pump partially reduces the amount of fuel supplied to the engine, resulting in a decrease in the developed torque and a decrease in the ability to jerk. Engine overload control is carried out by a built-in electronic unit.
Turbocharged engines
The fuel system operates in the same way as on non-turbo engines. However, the idle control system and the anti-jerk system are now controlled by the diesel engine's electronic control system (EDS), which also controls the intake pressure (turbo pressure) and an exhaust gas recirculation system.
Precautionary measures
Many of the operations described in this chapter involve disconnecting fuel lines, which may cause some fuel to leak out. Please read the Warnings below and the information before starting work "Safety first!" at the beginning of this guide.
Warning: Under no circumstances should diesel fuel come into contact with the coolant hoses - wipe off splashes immediately. Hoses that have been contaminated with fuel for a long time must be replaced. Diesel fuel systems are especially sensitive to the ingress of dirt, air and water. Pay special attention to cleanliness when working on any part of the fuel system. Thoroughly wipe the area around the fuel system connections before disconnecting them. Store dismantled parts in tightly closed containers to prevent contamination and condensation from entering the system. Use only a lint-free cloth and clean fuel for flushing. Do not use compressed air to purge the system during operation.
Caution: When working on any part of the fuel system, avoid skin contact with diesel fuel - wear protective clothing and gloves when handling fuel system components. Ensure good ventilation in the work area to avoid high concentrations of diesel fuel vapors.
Warning: Injectors operate at extremely high pressure and the jet of fuel from the injector nozzle can injure the skin with all possible unpleasant consequences. Exercise extreme caution when working with injectors. Never place your hand or any other part of your body under the injector nozzles. You must strictly adhere to the rule that work involving pressure testing of injectors must be carried out by dealers or specialists in diesel fuel equipment.