A very cold engine may not reach the ignition temperature when compressing the air. In this case, the engine needs to be warmed up. For this purpose, each swirl chamber has a glow plug that heats the combustion chamber. In order for a cold engine to start better, the injection moment of the high-pressure fuel pump (high pressure fuel pump) shifts in the advance direction, due to which the fuel is injected into the hot air earlier. As soon as the engine reaches its operating temperature, the injection moment is automatically reset. The injection moment is adjusted by the DDE control unit (DDE - Digital Diesel Electronics), which also controls the amount of fuel injected and the boost pressure from the turbocharger.
Fuel from the tank is supplied to the engine by means of a fuel pump and a high-pressure fuel pump located in the fuel tank. The high-pressure fuel pump creates the necessary high pressure for injecting it into the engine (about 160 bar), and the fuel is distributed among the cylinders in accordance with their operating order. The amount of fuel injected is determined by the DDE control unit depending on the position of the gas pedal, which is determined by a potentiometer. Through the injectors, diesel fuel is injected at the right moment into the pre-chamber of the corresponding cylinder. Due to the shape of the pre-chamber or swirl chamber, the incoming air flow acquires a swirl-like motion, i.e. it is mixed optimally with the injected fuel.
Before the fuel gets to the injection pump, it passes through a fuel filter, which cleans it from impurities and water. In this regard, it is very important to remove water from the filter in accordance with the maintenance plan and replace it. The injection pump is a maintenance-free unit. All its moving parts are lubricated with diesel fuel. The injection pump is driven by the crankshaft using a chain.
Since the diesel engine operates by self-ignition and cannot be stopped by disconnecting the voltage from the ignition system, there is a solenoid valve on the fuel injection pump. When the ignition is turned off, the supply voltage to this valve is disconnected, and the valve closes the fuel supply channel. The engine then stops. When the engine starts, voltage is supplied to the valve from the ignition switch, and the valve opens the fuel channel.
The DDE control unit detects faults in the injection system and stores their codes in the memory. In the workshop, using the diagnostic device (motor tester), which connects to the control unit, reads fault codes and then erases them.
[The article was copied from an online resource: «BMWMAN.ru»]