S-class W202 Mercedes

1993-2000 of release

Repair and car operation

W202 Mercedes
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Greasing system
+ 5. Cooling system
+ 6. Heating, ventilation
- 7. Ignition system
   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 a diesel engine
+ 8. Fuel system
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electroschemes

b47c026d b47c026d

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 to temperature which is maintained by a hand.
2. Remove a cross-section pipe of the air filter.
3. 4-cylinder engine: unscrew on a cover of a head of the block of cylinders a protective casing of wires of a high voltage (5/1).
4. 6-cylinder engine: unscrew a protective casing of wires of a 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. Thus pull only for tips, instead of for wires.
6. If possibly, carefully blow the 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 a working condition of the engine from this. The following rules are fair.
Electrodes and insulators:
  – cреднесерый 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 measuring shchupy a gap between electrodes. Preset value: 0,8 mm.
9. For gap establishment between contacts unbend a lateral electrode. For this purpose knock sideways on a lateral electrode. At bending back support a small screw-driver edge of a carving of a candle, but at all the electrode middle 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 to it, because at 4-клапанных candle engines deeply sit in the nests. So it is recommended to apply specially to Mercedes engines the corresponding candle key of HAZET 2776.

12. Hardly tighten spark plugs with the moment of 25 N of m.

The 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. Get contact tips of spark plugs. Alternately moving there-here, check a rigid nozzle of contact tips of spark plugs and wires of a high voltage.
14. 6-cylinder engine: mount ignition coils together with nests of wires.
15. Screw protective casings on a cover of heads of the block of cylinders. Establish a cross-section pipe of the air filter and fix it shlangovy 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, 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 engines in volume of 2,2 and 2,8 l thanks to system of detonation regulation, automatic coordination with the corresponding quality of fuel is carried out.

At engines in volume of 1,8 and 2,0 l coordination is carried out by means of removal of the leveling tip. Thanks to it, ignition is switched to other characteristic of ignition. This new characteristic of ignition allows to maintain 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 a stekloomyvatel and raise this tank.
2. Remove leveling tip (R16/7) which is near the regulating device of the engine (PMS).
3. If gasoline is again applied to cars with the high-forced engines, octane number 96–98, get leveling tip.

When using gasoline for cars with moderately forced engines it is possible to reduce capacity and to increase fuel consumption. Aspire to avoid some full gas.

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