- fuel tank with fuel level sensor, electric pump and suction jet pump;
- piping systems with fuel filter;
- main fuel pump and high pressure pump (NVD);
- distribution line;
- adapter
- injectors;
- pressure limiting valve;
- bimetallic valve;
- fuel cooler;
- expansion tank with dust filter;
- fuel management systems (DDE system).
Fuel electric pump (2), located in the fuel tank (1), feeds the booster pump with fuel. To create the necessary pressure for fuel injection, HP is used (21), which creates it in a hydraulic accumulator (24), for all injectors (25). An additional pump is installed between the low pressure fuel pump and the electric fuel pump of the tank - the main one (22), which supports the fuel tank pump when fuel consumption is high.
Fuel is supplied to HP from the fuel pump located in the tank through the supply pipelines, through the main pump and the fuel filter. NVD feeds the injector with fuel through a hydraulic accumulator.
By means of a pressure limiting valve included in the engine supply circuit, this boost pressure is kept constant. The valve is installed on the HP.
The fuel leaving the injectors and HPP enters the bimetallic valve (27), which distributes the amount of return flow depending on the temperature of the fuel. At low fuel temperatures, most of it again enters the supply pipeline in front of the main pump through the adapter (20) with 5 outlets, thus accelerating fuel heating at low outside temperatures. If the fuel temperature is high, then most of it is returned through the fuel cooler (28) and a return line to the fuel tank. This prevents excessive heating of the fuel at high outside temperatures.
Fuel return flow can be, under extreme operating conditions, large and hot. For example, when driving uphill or with a trailer. Therefore, through the throttle located in the adapter, part of the fuel is diverted directly to the supply pipeline. This measure additionally prevents excessive heating of the fuel in the tank.
Diesel fuel does not evaporate well, so there is no need for an adsorber. Fuel vapor condensate from the expansion tank (15) returns to the fuel tank. When refueling, the tank is vented through the filling vent line (7) in the filler neck.
Fuel tank
Fuel tank (1) designed to store the necessary fuel supply during the movement of the car. A two-section plastic fuel tank, saddle type, is located under the rear seat cushion and secured to the body with tie-down bands. Its capacity is 93 liters. The current supply of fuel and its consumption are controlled by two level sensors, each in its own section, information is displayed on a pointer-type device, the onset of a reserve (critical) fuel volume is fixed by an indicator on the instrument panel. The tank is equipped with a ventilation system through an expansion tank and a filter.
Fuel pump and filter
Fuel pump (2) rotary, submersible type, with electric drive produced by the company «Bosch» (Germany) installed in the right half of the fuel tank (looking in the direction of travel).
To maintain the required fuel pressure in high power modes, a main fuel pump is installed in the power supply system, which supplies an increased amount of fuel that exceeds its consumption by the engine. This pump is controlled by the electronic unit of the system «ECR» and is located in the luggage compartment on the right side. The fuel demand characteristics are stored in the control unit, which calculates the total amount of fuel required from the following values - the fuel demand of the engine as requested by the DDE control unit and the fuel required for lubrication and cooling of the high pressure pump (NVD).
The fuel filter is installed on the discharge pipeline after the main fuel pump. The filter housing contains a porous filter element with a retention capacity of 8 - 10 microns and a filtering surface of about 7500 cm2. The fuel filter has a pressure sensor that turns on the main pump.
Fuel injection system
The engines are equipped with a digital engine management system (Tssud) electronic type.
Attention!
- It is allowed to disconnect the wires from the AB terminals only when it is provided for by the work methodology. When the AB is turned off, the fault codes entered into the memory of the ECU-KSUD, the settings of the audio equipment and the anti-theft system locks are erased.
- Disconnection of plug connections (ShS) only be carried out with the ignition off.
- If the injection system malfunctions, check the condition of the loop before proceeding with troubleshooting in the ECU-CMD or other control element.
The TsSUD is designed to control all engine workflows to ensure the specified parameters of power, efficiency and toxicity of the car. It is also entrusted with the functions of controlling the automatic transmission, elements of the brake system - ABS, DSC, RDC, EDC, AGR and a number of other functions.
On cars «BMW» digital engine management systems are installed «DDE 4.0» on M57 and type «DDE 5.06» on M57TU - («Digitale Diesel Elektronic»).
Fuel injection control subsystem
The fuel injection control subsystem is an advanced electronic fuel injection system with a hot-wire mass air flow meter.
The principle of operation of the fuel injection control subsystem is as follows. Electric fuel pump (2) takes fuel from the tank and delivers it under pressure through the main pump (22) and filter (23) fuel cleaning to HP (21), then to the accumulator (24), connected to each cylinder through the fuel injection solenoid valve - injector (25).
The fuel pressure regulator mounted on the HP housing maintains a constant injection pressure created in the hydraulic accumulator and drains excess fuel into the tank, i.e. it ensures fuel circulation in the system and eliminates the formation of vapor locks in it. The fuel pump in the tank is switched on by the command of the DDE-ECU, which is activated at an engine speed of 30 min-1, when the starter is turned on, after the glow plugs have warmed up. When the engine is not running, an emergency shutdown of the fuel supply is provided if the engine has stalled as a result of an accident or an accident.
Each injector is controlled by a separate amplification output stage of the ECU-KSUD. This ensures the accuracy of the injected fuel dosage and its quick adjustment when the engine load changes.
Hydraulic accumulator (24) is a cavity with nests (holes) for the installation of pressure pipelines of injectors, a pressure sensor and a fitting for supplying a pipeline from HP. The hydraulic accumulator provides fuel supply under the same pressure to the injectors. Its volume is specially designed to ensure noise reduction during changes in operating conditions and pressure drops.
Injector (solenoid valve injectors) designed for metered supply of fuel injected into the combustion chamber of the engine. They are mounted on the cylinder head. The amount of injected fuel depends on the injector open time, which is determined by the ECU-ECU based on information received from the sensors.
Difficult starting, inability to start, as well as unstable idling of the engine, indicate a possible malfunction of the injectors. The crankshaft position sensor is mounted on the cylinder head, tied to the position of the camshaft and is designed to determine the position of the pistons in the cylinders, which determines the moment and amount of fuel supplied at the same time. It is built on the use of the Hall effect and generates an impulse of the position of the first cylinder at top dead center (TDC) compression stroke, which is the reference signal for the start of counting. The crankshaft speed sensor is installed on the cylinder block, above its flywheel and is designed to determine the engine crankshaft speed to generate a control signal for opening the injectors. It is based on the use of the Hall effect and generates an impulse of one full revolution of the crankshaft, which is a reference signal for calculating the engine speed and its instantaneous angular position.
The coolant temperature sensor is an NTC resistor, i.e. its resistance decreases as the temperature rises. While the engine is warming up, the ECU-ECU ensures the enrichment of the fuel mixture based on an electrical signal from a temperature sensor installed in the cylinder head.
The boost pressure sensor is designed to change the geometry of the TC, which allows you to optimally select the boost pressure, depending on the engine speed. A voltage of 5.0±0.25 V is applied to the sensor and it has measurement limits of 50–240 kPa.
All engine fuel elements are interconnected by fuel pipelines and hoses on nipple or clamp connections. If the engine does not start, starts with difficulty or stalls after starting, as well as with increased fuel consumption and an increased content of toxic compounds in the exhaust gas, it is necessary to check the serviceability of the coolant temperature sensor.
Additional functions of the central control system are self-diagnosis, control of the maximum permissible engine speed, turning on the BMW X5 E53 fuel pump, AB voltage control, communication with other systems, such as automatic transmission, ABS, ASC, RDC, ride height control, rain intensity sensor, airbags.
The self-diagnosis system detects malfunctions in the operation of the ECU-CSDC and enters them into memory in the form of codes. In the event of a malfunction of the coolant temperature sensors, the air flow meter, the system switches to work according to the average values included in the engine control program. Reading the codes at the workshop allows you to quickly identify the cause of the malfunction and eliminate it.
As soon as the engine speed reaches the maximum value, on command from the ECU-CSUD, the fuel supply to the engine cylinders is interrupted by turning off the injectors.
Fuel tank expansion tank
And although the degree of volatility of diesel fuel is very low, the design includes an expansion tank (15) fuel vapors, which is designed to condense diesel fuel vapors by expanding them and returning diesel fuel to its tank. The expansion tank is connected to the atmosphere through a dust filter (17).