Mercedes S-Class W-140

1991-1999 of release

Repair and car operation

Mercedes S-Class
+ Mercedes-Benz Cars of a class S (W-140)
+ Operation manual
+ Routine maintenance
+ Engine
+ Systems of cooling, heating
- Power supply system and release
   + the Power supply system and injection of fuel of the petrol engine - the general information
   + System of injection of fuel of the diesel engine - the general information
   + Control system of injection of fuel and HFM-SFI ignition (6-cylinder petrol engines)
   + Control systems of the LH-SFI and ME-SFI engine (8-cylinder petrol engines)
   + Control systems of injection of fuel and ME-SFI and LH-SFI ignition (12-cylinder petrol engines)
   + Control system of fuel injection (diesel engines of the Om603.971 series)
   + Control system of fuel injection (diesel engines of the Om606.961 series)
   + turbo-supercharging System - the general information
   Systems of decrease in toxicity of release - the general information
   System of production of the fulfilled gases - the general information
   Catalytic converter (petrol models)
+ engine Electric equipment
+ gear shifting Box
+ Avtomaticheckaya transmission
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment


Catalytic converter (petrol models)

The catalytic converter has the central ceramic part of a cellular design (3) covered with a layer of the carrier. On a layer of the carrier there are the salts of precious metals operating as converters. The catalytic converter is fixed in the case (1) by means of the insulating basic layer (2) compensating at the same time thermal expansions of the catalytic converter.

To reduce by means of the catalytic converter harmful emissions, systems of injection should dose out precisely amount of the injected fuel necessary for combustion. The sensor of oxygen is in a reception pipe in front of the catalytic converter and is washed by a stream of the fulfilled gases. The sensor of oxygen represents the electronic sensor measuring the content of oxygen in final gases and representing its type of fluctuations of tension. Information from the sensor of oxygen is transferred to the control unit of system of injection. The received value allows to regulate structure of an air-petrol mix. On the one hand it is necessary, as service conditions (the idling, full gas), on the other hand, constantly change as optimum reburning of fuel in the catalyst occurs only in this case if final gases contain fuel enough.

That in the catalyst there was a fuel reburning, it is necessary to have temperature 300 - 800°С. For this purpose the bigger content of fuel in a mix, than for pure burning is necessary.

Applied catalytic converters of petrol engines represent so-called three-functional devices. In adjustable process of transformation oxidation of an oxide of carbon (WITH) and hydrocarbon (NANOSECOND), and also reduction of concentration of oxides of nitrogen (NOx) is carried out.

Security measures for an exception of damages of the catalytic converter

For an exception of damages of the sensor of oxygen and the catalytic converter it is necessary to fulfill the following requirements:
  • Surely apply only unleaded gasoline;
  • Start of the heated-up petrol engine by pushing or towage is authorized to carry out only in one attempt and at distance no more than 50 m. Better for this purpose to apply a starting cable. Not burned down fuel at ignition can lead to an overheat of the catalytic converter and its destruction. Remark: Start of cars with AT is for technical reasons impossible;
  • At difficulty with start of the engine it is not necessary to include a starter too long. Continuous injection of fuel is thus made. It is necessary to reveal and eliminate a cause of defect;
  • If there are malfunctions with ignition system, at determination of their character it is necessary to exclude fuel injection at starter inclusion. For this purpose disconnect the relay of the fuel pump;
  • Never spend fuel in a fuel tank completely;
  • At emergence of interruptions in ignition do not raise number of turns of the engine and immediately eliminate malfunction;
  • Apply only the recommended spark plugs;
  • Do not carry out spark check with the disconnected shtekerny connection of a spark plug;
  • Carrying out test of operation of the cylinder by disconnection of a wire of ignition from its candle is not allowed. Thus not burned down fuel gets to the catalytic converter;
  • Do not stop the car over dry foliage or a grass. The system of production of the fulfilled gases around the catalytic converter very hot also radiates heat even after an engine stop;
  • Do not put on elements of system of release of means for protection of the bottom of the car;
  • It is not allowed to change a design of heat-shielding screens;
  • When filling engine with oil especially pay attention to exceeding at all the level designated on the index as by Max. Excess of oil owing to incomplete combustion arrives in the catalytic converter and can damage its covering from the alloyed metal or completely to destroy the catalytic converter.