Mercedes of the S-class W202

1993-2000 of release

Repair and operation of the car

Mercedes W202
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Lubrication system
+ 5. Cooling system
+ 6. Heating, ventilation
- 7. System of ignition
   7.2. Safety measures at repair of electronic system of ignition
   7.3. Ignition coils
   - 7.4. Spark plugs
      7.4.2. Index of kalilny number
   + 7.5. Device of a preliminary warming up of the diesel
+ 8. Fuel system
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electrical circuitries

7.4. Spark plugs

7.4.1. Removal, installation, check


Spark plugs should be changed every 2 year or through 30 000 km.

1. Cool the engine up to the temperature which is maintained by a hand.
2. Remove a cross pipe of the air filter.
3. 4-cylinder engine: unscrew on a cover of a head of the block of cylinders the protection cover of wires of high voltage (5/1).
4. 6-cylinder engine: unscrew the protection cover of wires of high voltage (5/1) on a cover of a head of the block of cylinders. Take ignition coils together with the connected wires of a chain of management and put them aside.
5. Weaken all contact tips of spark plugs, then remove them. At the same time pull only for tips, but not for wires.
6. If it is possible, carefully blow compressed air of a niche of spark plugs.
7. Unscrew spark plugs (R4) by means of a suitable candle key, or a key of HAZET 2776 and check appearance of a screw part of a candle. Having some experience, it is possible to draw conclusions on the working condition of the engine from this. The following rules are fair.
Electrodes and insulators:
  – srednesery color – normal combustion and normal work of a spark plug.
  – black color – too rich gas mixture.
  – light gray color – too grown poor gas mixture.
  – violet color – interruptions in work of the corresponding spark plug or bad sealing piston rings.
8. Check the measuring probe a gap between electrodes. Preset value: 0,8 mm.
9. For establishment of a gap between contacts unbend a side electrode. For this purpose knock sideways on a side electrode. At bending back support by the small screw-driver edge of a carving of a candle, but at all not the middle of an electrode as differently the electrode can be damaged.
10. Clear a carving on candles and in a head of the block of cylinders.
11. A hand screw in spark plugs up to a reliable prileganiye on a head of the block of cylinders.

Inserting candles, do not warp them. It is necessary to pay attention because at 4-valvate engines of a candle deeply sit in the nests to it. So it is recommended to apply the corresponding candle key of HAZET 2776 especially for Mercedes engines.

12. Hardly tighten spark plugs with m 25 N.' moment.

Too hardly tightened spark plugs at their twisting can become torn or damage a carving in a head of the block of cylinders. In this case the carving of a screw part of a candle can be restored by means of UTC inserts (or Heli-Coil).

13. Spread contact tips of spark plugs. Alternately moving to and fro, check a rigid nozzle of contact tips of spark plugs and wires of high voltage.
14. 6-cylinder engine: mount ignition coils together with nests of wires.
15. Screw protection covers on a cover of heads of the block of cylinders. Establish a cross pipe of the air filter and record it hose clips.

Coordination with quality of fuel

S-class engines, as a rule, need unleaded gasoline for the high-forced engines with octane number 96-98 (on ROZ 95). If providing with this fuel is not guaranteed, for example, abroad, then it is possible to refuel temporarily and unleaded irregular gasoline (on ROZ 91). The octane number determined by ROZ indicates detonation firmness of fuel.

At the 2,2 and 2,8 l engines thanks to system of detonation regulation, automatic coordination with the corresponding quality of fuel is carried out.

At the 1,8 and 2,0 l engines coordination is carried out by means of removal of the leveling plug. Thanks to it, ignition switches to other characteristic of ignition. This new characteristic of ignition allows to operate the car when using unleaded gasoline for cars with moderately forced engines, octane number to 92 on ROZ 91.
1. Weaken the plastic screw of fastening of a tank of windscreen washer and raise this tank.
2. Remove the leveling plug (R16/7) which is near the control device of the engine (PMS).
3. If gasoline is again applied to cars with the high-forced engines, octane number 96–98, spread the leveling plug.

When using gasoline for cars with moderately forced engines it is possible to reduce power and to increase fuel consumption. You seek to avoid full gas.

Gasoline with higher octane number, for example, "Super plus" (ROZ 98), it is possible to apply always without switching of the leveling plug.