4.2. Check of compression pressure

Implementation of the procedure of check of compression pressure will require the help of the assistant.

The measurement of compression pressure allows to make general idea about current state of such internal components of the engine as laying of heads of cylinders, elements of the valvate mechanism, pistons and piston rings. The analysis of results of check allows to define whether the engine needs capital recovery repairs, or it is enough to replace only sealing laying of a head of cylinders. Measurement is performed by means of a kompressometr.


  1. Warm up the engine up to the normal working temperature (about the 80th hail.) also muffle it.
  2. Make sure of completeness of a charge of the rechargeable battery.
  3. On petrol models turn out all spark plugs (see the Section Check and replacement of spark plugs and the module of ignition).
  4. Prepare компрессометр and screw its nozzle in a candle opening of one of cylinders.
  5. Completely open a butterfly valve and, turning the engine a starter, consider indications of a kompressometr. Write down result of measurement.

Time of carrying out measurement has to be as it is possible well.

  1. Repeat the procedures described in items 4 and 5 for the remained engine cylinders.
  2. Compare results of measurement by requirements of Specifications.
  3. The compression grows in the serviceable engine very quickly. The low value shown after the first cycle, increasing with the subsequent cycles indicates wear of piston rings. The low value after the first cycle which is not increasing after the following indicates existence of leaks via valves, or the punched laying of a head of the cylinder (also the crack in a head can be the cause). Can lead existence of a deposit on plates to decrease in a compression of valves.
  4. The results received at measurement of a compression have to be approximately identical to all cylinders. If pressure is in any cylinder at the level of minimum admissible and even below, then for clarification of the reason pour in the cylinder through a candle opening in a teaspoon of motive oil and repeat measurement of a compression.
  5. If oil addition temporarily improved a compression, most likely, wear of the piston, rings or the cylinder is the reason of its decrease. If increase in a compression did not happen, then it is possible to assume that the reason – in leakage of valves or the punched laying of a head of the block.
  6. The low compression in two next cylinders almost for certain is a consequence of breakdown of laying of a head. Availability of cooling liquid in combustion chambers or in a case of the engine will confirm this assumption.
  7. If the compression in one of cylinders differs from the others more, to us on 2 atm, besides turns of idling are unstable, then the reason, perhaps, excessive wear of a cam of the camshaft.
  8. After conducting check disconnect компрессометр and install the being removed components.

Features for the diesel engine

On the diesel engine компрессометр is established in openings for a glow plug therefore previously execute the operations described below.


  1. Separate the socket of nozzles.
  2. Remove from a turbocompressor the top section of the inlet pipeline with the MAF sensor.
  3. Remove the top cover of the engine.
  4. Disconnect a delivery hose of a turbocompressor from the inlet pipeline.
  5. Remove the top section of the inlet pipeline.
  6. Separate sockets of the EGR valve, the sensor of temperature of fuel and the sensor of absolute pressure.
  7. Remove toplivopodayushchy tubes of nozzles of cylinders 1, 3, 4 and 5.

Previously dump pressure in a power supply system.

  1. Give fixture of the returnable line of the back block of cylinders.
  2. Remove glow plugs (see the Head Sistemy of electric equipment of the engine).