General information
When a diesel engine is running, clean air is sucked into its cylinders and compressed to high pressure. The air temperature rises to 700 - 900°C, which exceeds the ignition temperature of diesel fuel. The fuel is injected into the cylinder with some advance and ignites. Thus, spark plugs are not used to ignite the fuel.
Fuel is sucked by the high-pressure fuel pump (HPFP) directly from the tank. In the HPFP, the fuel is compressed to the pressure required for injection. Injection is carried out in a manner similar to the ignition order in a gasoline engine.
When the fuel supply is running low - a warning light comes on on the instrument panel - you should refuel the car without delay.
In order to reduce the toxicity of exhaust gases, a catalytic converter is included in the standard equipment of all diesel models. At the same time, the recirculation system ensures a significant reduction in the content of nitrogen oxides in the exhaust gases, part of the exhaust gases is mixed with the air sucked into the engine, which ensures a decrease in the concentration of oxygen in it and, accordingly, a reduction in the ignition delay and a decrease in the combustion temperature. The result of all these processes is the minimization of the formation of nitrogen oxides (NOX) in the combustion products. The process of recirculation of exhaust gases requires precise dosing, since otherwise the level of carbon particles (soot) in the combustion products increases. Dosing is carried out by including a special meter in the system circuit - the information coming from the meter allows the electronic module to control the recirculation process.
On 1.7L SOHC engines fuel injection is carried out into the pre-chambers of the cylinders, 1.7L DOHC and 2.0L engines - directly into the combustion chambers.
The high-pressure fuel pump has electronic control, which guarantees compliance with strict modern requirements for the content of toxic components in engine exhaust gases. The brain of the control system is an electronic module built into the pump assembly, continuously analyzing data coming from a whole complex of information sensors:
Engines 1.7L SOHC
- Accelerator Pedal Position Sensor informs control units about the position of the gas pedal;
- Coolant Temperature (ECT) Sensor informs control units about the engine operating temperature;
- Mass Air Flow (MAF) Sensor informs the control units about the mass and temperature of the air sucked into the intake air duct;
- Crankshaft Position Sensor (CKP) informs control units about the position and speed of rotation of the crankshaft;
- Boost pressure sensor informs control units about the pressure in the intake manifold;
- Fuel injection pump sensors and regulators (built-in) are used by control units to calculate and control the timing and amount of fuel injected into the engine;
- Clutch sensor used by control units when performing cruise control functions;
- K/V activation sensor switch informs control units about turning the air conditioner on or off.
1.7L DOHC and 2.0L engines
- Accelerator Pedal Position Sensor informs control units about the position of the gas pedal;
- Coolant Temperature (ECT) Sensor informs control units about the engine operating temperature;
- Intake Air Temperature (IAT) Sensor informs the control units about the air temperature in the intake air duct;
- Mass Air Flow (MAF) Sensor informs the control units about the mass of air passing through the intake air duct;
- Oil temperature sensor (2.0L engines) informs control units about engine oil temperature;
- Crankshaft Position Sensor (CKP) informs control units about the position and speed of rotation of the crankshaft;
- Boost pressure sensor informs control units about the pressure in the intake manifold;
- ABS control module informs control units about the vehicle's speed;
- Atmospheric pressure sensor (BARO) informs control units about atmospheric pressure;
- Fuel temperature sensor informs control units about fuel temperature;
- Fuel injection pump shaft position sensor used by control units when calculating and setting fuel injection timing;
- Oil pressure alarm sensor used by the engine ECM to control the operation of the warning lamp on the instrument panel;
- Clutch sensor used by control units when performing cruise control functions;
- K/V activation sensor switch informs control units about turning the air conditioner on or off.
All data received from the information sensors are processed by electronic control units, which, based on its analysis, control the timing and quantity of fuel injection, ensuring optimal performance characteristics of the power unit regardless of changes in external factors. The engine ECM controls the injection timing via the fuel injection pump control unit, ensuring reliable engine starting at any ambient temperature, its fastest warm-up, and maximum output in all driving modes, including acceleration and engine braking.
Original posted on the website: OPELBOOK
The basic setting of injection moments is made when installing the fuel injection pump on the engine. During the operation of the unit, changes in this characteristic occur automatically according to ECM commands via the cam actuator.
The fuel supplied to the engine is dosed using injection quantity and timing valves built into the high-pressure fuel pump. The valves are triggered by commands issued by the high-pressure fuel pump control unit, usually located at the top of the pump. A special ring is installed on the main rotor of the high-pressure fuel pump. The rotor position sensor determines the position and speed of rotation of the rotor. The sensor operates on a principle similar to the crankshaft position sensor. Four marks are applied to the rotor - in accordance with the number of cylinders. The pump control unit receives the necessary information from the engine control unit (ECM) and calculates the moments and duration of fuel supply. The internal components of the high-pressure fuel pump allow very accurate calculation of these parameters, which ultimately leads to increased engine efficiency and reduced toxicity of exhaust gases.
On diesel models there is no gas cable - its functions are performed by the accelerator pedal position sensor. The sensor continuously informs the control unit about the pedal position, which allows the ECM to accurately calculate the injection parameters. Idle speed is also regulated by the control unit and is not subject to manual adjustment. Analyzing information coming from various sensors, the control unit calculates the number of revolutions, adjusting them depending on the load and engine temperature.
The pump is connected to injectors metal tubes. Each injector delivers fuel to the combustion chambers through five holes. This ensures uniform distribution of fuel in the combustion chamber and precise direction of fuel delivery. The fuel injection system is a direct injection system. The piston crowns contain vortex chambers, providing a swirl of the fuel entering the combustion chambers. To optimize fuel combustion, the injectors open in two stages (for this purpose, there are two springs inside each nozzle). When the injector opens, a small amount of fuel hits the internal components of the injector, lubricating them, and returns to the fuel tank.
The cold engine warm-up is controlled by the engine control unit and the high-pressure fuel pump control unit. When the engine is cold, the injection timing is shifted by the high-pressure fuel pump control unit. The engine control unit, in turn, controls the glow plugs. Glow plugs are installed in each cylinder and are switched on before starting the engine, working during the engine cranking by the starter and for some time after starting the engine. Spark plugs make starting a cold engine much easier. After turning on the ignition, a control lamp lights up on the dashboard (see Chapter User manual), signaling the activation of glow plugs. As soon as the lamp goes out, you can start the engine. In very cold weather, the spark plugs continue to work for some time after the engine has started, ensuring the stability of the latter's operation and reducing the level of toxic components in the exhaust gases.
Due to the high starting properties, pre-heating is only necessary on direct injection models at temperatures below -10°C.
If the sensors receive information indicating the occurrence of an abnormal situation, the ECM switches to an emergency operating mode, when the base values of the corresponding parameters are substituted for inadequate signals - the efficiency of the engine output in this mode is naturally reduced. The driver is warned about the ECM entering emergency mode by the activation of the failure indicator lamp on the vehicle instrument panel (see Chapter User manual), the corresponding diagnostic code is entered into the processor memory (see Chapter Engine electrical equipment).
Under certain circumstances, the vehicle's behavior may not change at all. The only sign that the ECM has switched to emergency mode may be an increase in exhaust toxicity. Keep in mind that after replacing a faulty sensor with a working one, the system will not automatically switch to normal mode on its own - you should clear the processor memory from the diagnostic codes contained in it. Even if the reason for the system switching to the emergency safe mode was a wiring break, the processor memory should be cleared after it.
If the warning light comes on, the vehicle should be taken to an authorized Opel service station as soon as possible for detailed diagnostics using special equipment and for the necessary repairs to be carried out.
Diagnostic equipment (scanner type reader) connects to the DLC connector located under the decorative trim in front of the parking brake lever.
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