Mercedes W124

since 1985-1995 of release

Repair and car operation

W124 Mercedes
+ Governing bodies and control devices
+ 2. Maintenance (diesel engines)
+ 4. Repair of 6-cylinder petrol SOHC engines
+ 5. Repair of 6-cylinder petrol DOHC engines
+ 6. Repair of the diesel engine established in the car
+ 7. Major maintenance of engines
+ 10. System of injection of BOSCH CIS-E fuel (KE-JETRONIC)
+ 11. System of injection of BOSCH HFM fuel
- 12. Fuel system of diesel engines
   12.2. General information
   12.3. Air filter
   12.4. Fuel level sensor
   12.5. Fuel tank
   12.6. Inlet collector
   12.7. Accelerator cable
   12.8. Fuel pump of a high pressure
   12.9. The pumping-up fuel pump
   12.10. Mechanism of adjustment of the moment of injection, asterisk of the fuel pump
   12.11. Moment of injection of the fuel pump of a high pressure
   12.12. Fuel nozzles
   12.13. Electronic control system of turns of idling (ELR)
   12.14. Electronic anti-detonation system ARA
   12.15. Electronic control system of the diesel engine
   12.16. System of protection of the engine from an overload
   12.17. Fuel thermostat
+ 13. Fuel system of diesel engines
+ 15. System of ignition of 4-cylinder petrol engines
+ 16. System of ignition of four-cylinder petrol engines
+ 19. Mechanical transmission
+ 20. Automatic transmission

12.2. General information

Engines without a turbo-supercharging

The fuel system of the diesel engine includes a fuel tank, the fuel pump of a high pressure, the fuel filter established on the fuel pump and the main fuel filter, submitting and returnable топливопроводы and the fuel nozzles established on one on each cylinder.

The fuel pump is put in action by a chain and rotates with turns twice smaller, than turns of a cranked shaft of the engine. Fuel from a fuel tank gets the fuel pump via the primary and main filter and then under a high pressure moves to fuel nozzles.

The moment of injection of fuel is established by turn of the fuel pump on fastening arms. At operation of the engine the moment of injection is defined by mechanically fuel pump depending on the provision of a pedal of an accelerator and engine turns. The moment of injection of fuel can be changed by means of the adjusting device located sideways of the fuel pump.

The fuel nozzle represents the valve which opens at strictly certain pressure of fuel. The spray being on the bottom end of a nozzle, forms a torch of sprayed fuel of a demanded form. Otsechka of fuel is made by a needle under the influence of a nozzle spring. The spray and a needle are knot of precision accuracy and demand the accurate address at repair. Surpluses of fuel after an otsechka are pumped over along a needle, greasing it and on the return pipeline are taken away in a fuel tank.

Serviceability and the correct adjustment of nozzles are very important for normal operation of the engine. If the spray of a nozzle does not provide a torch of a demanded form or there is a bad otsechka, the engine starts to work with vibration, there are strong mechanical knocks, pressure raises. It should be noted that sprays from different models of engines are outwardly identical, but have different characteristics, in particular, a torch form therefore new sprays should be applied only what are calculated on this model.

Switching off of the engine is made by means of the vacuum switch which is established on the top part of the fuel pump of a high pressure. At key turn in the ignition lock in the situation "OFF" the vacuum switch connected to the lock of ignition, closes vacuum giving to the vacuum switch which in turn blocks supply of fuel to the fuel pump, and the engine stops.

Adjustment of turns of idling of the engine is made by a mechanical regulator which is built in the fuel pump of a high pressure. The mechanical regulator of centrifugal type changes the provision of a lath of the fuel pump via the podpruzhinenny lever. Adjustment of turns of idling is carried out by one or more executive mechanisms which change idling turns at emergence of loading. For example, at turning on of the amplifier of a steering, the conditioner, drive inclusion on models with an automatic transmission or start of the cold engine.

On later models with 6-cylinder engines and models with 4-and 5-cylinder engines with central air of air and an automatic transmission the electronic control system of turns of idling (ELR) is established. In this system the electronic control device supervises engine turns by means of the sensor established about a flywheel, and temperature of cooling liquid by means of the sensor which has been screwed in in a head of the block of cylinders. The ECU block compares the actual sizes to the sizes which have been written down in memory, and if necessary turns on the electromagnetic executive mechanism which moves a regulator of the fuel pump and changes turns of idling of the engine.

On some models with a mechanical transmission the system preventing breakthroughs of the engine (ARA) is established. This system on the basis of information on turns of the engine and temperature of cooling liquid excludes possibility of emergence of breakthroughs of the car at acceleration and delay. At approach to a breakthrough condition the executive mechanism established sideways of the fuel pump, quickly reduces amount of submitted fuel. The torque of the engine and a tendency to breakthrough as a result decreases vanishes. On models with 6-cylinder engines engine management is made by the electronic ELR device, and on other models the specialized electronic device.

Engines with a turbo-supercharging

Work of system of injection of fuel on engines with a turbo-supercharging is similar to work of system of injection of fuel on engines without a turbo-supercharging. On engines with a turbo-supercharging a control system of turns of idling and excluding breakthroughs of the engine cope an electronic control system of diesel engines (EDS) which also operates pressure in system of repeated burning of the fulfilled gases and a turbokompressor.

At works on fuel system, probably, a fuel effluence therefore it is necessary to be careful.


Do not allow hit of diesel fuel on hoses of system of cooling. Hoses which the long time influenced diesel fuel, it is necessary to replace.

The fuel system of the diesel engine is especially sensitive to pollution therefore at work on fuel system observe the maximum purity. Before a rassoyedineniye топливопроводов carefully clear them of dirt.

Do not use the compressed air for cleaning of elements of the fuel system established on the engine.

At check of work of fuel nozzles never hold up hands or any part of a body under the stream of fuel leaving a nozzle. Fuel leaves a nozzle under a high pressure and can get into a body through skin.