The fuel system includes a rear-mounted fuel tank, fuel filter, high pressure fuel pump, injectors, high and low pressure fuel lines.
Fuel supply devices in diesel engines are much more complicated than in gasoline engines. Their complexity is determined, first of all, by the fact that it is necessary to inject very small, only a few milligrams, portions of fuel into a high-pressure environment. These portions must be very accurately measured - it is the amount of fuel supplied that controls the operation of a diesel engine. This requires fast and accurate nozzles. A high compression ratio requires the use of appropriate fuel pumps - the pressure in the injector nozzle must reach several hundred bar. All this complicates and significantly increases the cost of the fuel supply system and, accordingly, the diesel engine itself.
AUDI A6 diesel vehicles use the EDC electronic engine management system (Electronic Diesel Control) BOSCH, which determines the amount and timing of fuel injection.
The use of an electronic engine management system has the following advantages:
- self-diagnosis system allows you to quickly identify defects in the engine. The system has an error memory that records all defects that appear during engine operation. In case of violation of the normal operation of the engine, at the service station, a special device can be used to retrieve from the memory the errors recorded in it:
- due to the exact dosage of fuel supplied to the engine in all operating modes, fuel consumption is reduced while maintaining the dynamic characteristics of the car;
- due to a more accurate dosage of fuel, as well as the use of a catalyst, the emission of harmful substances along with exhaust gases is reduced.
Engine management components are very reliable and virtually maintenance free. During maintenance, it is only necessary to replace the air and fuel filters. Since it is necessary to use complex expensive equipment to check, adjust and repair the engine control system, this work must be done at a service station.
As part of the maintenance, it is not necessary to adjust the idle speed and the speed limited by the regulator.
Pic. 4C.1. Location of elements of the EDC engine management system in the engine compartment with a 1.9-I-TDI engine
1 - air pressure and temperature sensor,
2 - electrical connector of the engine speed sensor,
3 - electrical connector of the fuel injector needle lift sensor,
4 - exhaust gas recirculation valve,
5 - coolant temperature sensor,
6 - electrical connector of the fuel pump,
8-pin for fuel temperature sensors, injection system fuel dispenser and forced idle.
7 - electrical connector of the fuel pump,
3-pin for engine stop valve and fuel injection timing.
8 - engine speed sensor,
9 - electronic engine control unit with fuses for glow plugs,
10 - fuel pump,
With fuel injection timing valves, engine stop valve and fuel temperature sensor.
11 - fuel injector with needle lift sensor,
12 - solenoid valve for boost pressure control,
13 - exhaust gas recirculation valve,
14 - air flow meter,
Note. The figure does not show the glow plug relay, the sensor for the accelerator pedal position and the brake light switch.
Pic. 4C.2. Diagram of the diesel engine fuel system
1 - fuel tank,
2 - fuel filter,
3 - fuel pump,
4 - fuel pump control unit,
5 - high pressure solenoid valve,
6 - fuel injection advance clutch - solenoid valve,
7 - fuel injection advance clutch,
8 - engine control unit,
9 - fuel injector,
10 - glow plug,
11 - glow plug control unit,
12 - coolant temperature sensor,
13 - crankshaft speed sensor,
14 - intake air temperature sensor,
15 - air flow meter,
16 - boost pressure sensor,
17 - turbocharger,
18 - exhaust gas recirculation valve,
19 - boost pressure regulator,
20 - low pressure pump,
21 - battery,
22 - instrument cluster,
23 - accelerator pedal position sensor,
24 - clutch switch,
25 - foot brake switch,
26 - speed sensor,
27 - regulator-limiter.
28 - air conditioner compressors,
29 - diagnostic connector.
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