Mercedes W124

since 1985-1995 of release

Repair and car operation

W124 Mercedes
+ Governing bodies and control devices
+ 2. Maintenance (diesel engines)
   3.2. General data
   3.3. Repair operations on the engine established in the car
   3.4. Check of pressure of compression
   3.5. Top dead point (VMT) of the piston of the first cylinder
   3.6. Cover of a head of the block of cylinders
   3.7. Pulley cranked shaft / quencher of krutilny fluctuations and nave
   + 3.8. Cover of a driving chain
   3.9. Check and replacement of a driving chain
   + 3.10. Mechanism of a tension of a driving chain, asterisk and uspokoitel of a chain
   3.11. Intermediate shaft
   + 3.12. Drive of valves, pushers and camshaft
   + 3.13. Head of the block of cylinders
   3.14. Oil pallet
   3.15. Oil pump
   3.16. Drive flywheel / plate
   3.17. Replacement of sealing rings of a cranked shaft
   3.18. Bearing replacement in an end face of a cranked shaft
   3.19. Check and replacement of a support of the power unit
+ 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
+ 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

3.4. Check of pressure of compression


Check of a condition of the engine can be made by measurement of pressure of compression in cylinders. If this check to make regularly, it is possible to learn in advance the beginning of wear of the engine, without waiting the moment when wear will be shown in low overall performance of the engine.

1. Warm up the engine to working temperature. Thus the accumulator should be completely charged. Unscrew spark plugs.
2. Disconnect electric wires from the ignition distributor. On engines with system of injection of fuel remove the relay of the fuel pump, and on models with carburetors disconnect the electric socket from the valve of an otsechka of fuel.
3. In an opening of a candle of the first cylinder establish компрессометр.
4. The assistant should press an accelerator pedal against the stop and turn the engine a starter. After a provorachivaniye of a cranked shaft or two turns pressure of compression should increase by one to a maximum, and then be stabilized. Make record of the maximum received result.
5. Similarly check other cylinders.
6. Pressure of compression in all cylinders should not differ more than on 1,5 bar. Pay attention that the size of compression should increase quickly on the serviceable engine. Low pressure of compression on the first turn of the cranked shaft, accompanied by gradual increase in pressure on the subsequent turns of a cranked shaft indicates wear of piston rings.
7. The low size of pressure on the first turn of a cranked shaft which slightly increases further, indicates a thinness of a prileganiye of the valves, the punched laying of a head of the block of cylinders or crack existence in a head of the block of cylinders. Wear of the ends of cores of valves can result in low pressure of compression also.
8. If pressure in one cylinder lowered, carry out the following test. Fill in through a candle opening in the cylinder of a little engine oil and check pressure of compression.
9. If oil filling in the cylinder increases pressure of compression, it specifies that the cylinder or piston rings is worn-out.
10. Low pressure in two next cylinders indicates a laying burn-out between cylinders.
11. If pressure in one cylinder is less for 20 %, than in the others, and the engine works unstably idling is points to a worn-out cam of a camshaft.
12. If pressure of compression is too high, it specifies that the chamber of combustion is covered with a thick layer of a deposit.
13. After this check screw in spark plugs, connect high-voltage wires and establish the relay of the fuel pump.