Mercedes S-Class W-140

1991-1999 of release

Repair and operation of the car

Mercedes S-Class
+ Mercedes-Benz cars of the class S (W-140)
+ Operation manual
+ Routine maintenance
+ Engine
+ Cooling systems, heating
- Power supply system and release
   + A 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 ignition of ME-SFI and LH-SFI (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)
   + System of a turbo-supercharging - 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
+ Automatic 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 carrier layer. On a layer of the carrier there are 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 harmful emissions by means of the catalytic converter, systems of injection has to dose precisely amount of the injectable 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 composition of air-petrol mix. On the one hand it is necessary as service conditions constantly change (idling, full gas), on the other hand, as optimum reburning of fuel in the catalyst happens only in this case if final gases contain enough fuel.

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

The used catalytic converters of petrol engines represent so-called three-functional devices. In adjustable process of transformation oxidation of carbon monoxide (SO) and hydrocarbon (NANOSECOND), and also reduction of concentration of nitrogen oxides (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 pushing or towage is allowed 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. At the same time the continuous injection of fuel is made. It is necessary to reveal and remove a cause of defect;
  • If there are malfunctions with system of ignition, when determining their character it is necessary to exclude injection of fuel at inclusion of a starter. For this purpose switch-off the relay of the fuel pump;
  • Never spend fuel in a gasoline tank completely;
  • At emergence of interruptions in ignition do not increase the speed of the engine and immediately eliminate malfunction;
  • Apply only the recommended spark plugs;
  • You do not carry out an inspection of a spark with the disconnected shtekerny connection of a spark plug;
  • Test of operation of the cylinder by disconnection of a wire of ignition from its candle is not allowed. At the same time 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;
  • You do not apply 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 the engine with oil especially pay attention to not to exceed the level designated on the index as Max at all. Excess of oil owing to incomplete combustion comes to the catalytic converter and can damage its covering from the alloyed metal or completely destroy the catalytic converter.