1. Crankshaft pulse sensor
2. Coolant temperature sensor
3. Charge air temperature sensor
4. Discharge pressure sensor
5. EGR changeover valve
6. Control unit DDE 2.1
7. High pressure fuel pump (injection pump)
In a diesel engine, clean air is sucked into the cylinders and subjected to strong compression. As a result, the temperature of the air in the cylinders rises above the ignition temperature of diesel fuel. When the piston is slightly above TDC, diesel fuel is injected into highly compressed air heated to +600°C. Diesel fuel ignites on its own, no spark plugs are required.
With a very cold engine, the ignition temperature is not reached by compression alone.
In this case, the engine must be preheated. To do this, each swirl chamber contains a glow plug that heats the air in the combustion chamber. In order for a cold engine to run better, fuel is injected into the hot air earlier. As soon as the engine has reached operating temperature, the injection timing is automatically shifted back. The start of injection is controlled by the DDE control unit (DDE = Digital Diesel Electronic), as well as regulation of the injection quantity and boost pressure for the turbocharger.
Fuel is supplied from the fuel tank by the supply fuel pump, as well as the injection pump to the engine. A high pressure of about 160 bar is created in the injection pump and the fuel is distributed to the individual cylinders according to the ignition order. The amount of fuel injected is determined by the DDE control unit, with a corresponding action on the accelerator pedal, whose position is monitored by a potentiometer. Through the nozzles, diesel fuel is supplied at a certain time to the vortex chambers of the respective cylinders. During the compression phase, the intake air acquires a certain swirling motion in the shape of the swirl chamber and is thus optimally mixed with the injected fuel.
Before fuel enters the injection pump, it passes through the fuel filter. There it is cleaned of dirt and water. Therefore, it is important to change the fuel filter according to the maintenance recommendations.
The injection pump does not require maintenance. All moving parts of the pump are lubricated with diesel fuel. The pump is driven by the crankshaft through a chain.
Since the diesel engine is a self-igniting device and does not turn off when the voltage in the ignition system is interrupted, it is equipped with a solenoid valve. When the ignition is turned off, the voltage on the solenoid valve is turned off, and the valve closes the fuel channel. This ensures that the fuel supply is cut off before the steering column lock is locked. When the engine is started with the starter switch, the solenoid valve is energized and the fuel passage is opened.
The DDE control unit monitors and prevents malfunctions in the injection system. OPEL workshops can provide a troubleshooting tool that connects to the control unit and interrogates and reads faults.
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