4.2. Check of compression pressure in cylinders

Results of check of compression pressure in cylinders allow to define the general condition of components of the top part of the engine (pistons, piston rings, valves, laying of a head of cylinders, etc.) and to qualitatively estimate degree of their wear. What is especially important, the analysis of information obtained as a result of check allows to narrow a range of the possible reasons of falling of a compression in cylinders, having rather precisely tied refusal to violations of functioning of quite concrete components, whether it be piston rings, valves, their saddles or laying of a head.

The engine has to be heated-up up to the normal working temperature, and the rechargeable battery is completely charged.


  1. Begin with a clearing of candle niches (blow them compressed air as which source in this case the ordinary bicycle pump perfectly will approach). The main objective is prevention of hit of garbage in cylinders during performance of measurements.
  2. Turn out from the engine all spark plugs (see the Head Routine maintenance).
  3. Record a butterfly valve in completely open situation.
  1. For dumping of pressure in a power supply system switch off ignition and take from the landing nest in the saloon assembly block a safety lock of the fuel pump, then start the engine and wait for its spontaneous stop — for dumping of residual pressure turn the engine 2-3 more times a starter, then switch off ignition and establish into place a safety lock.
  1. Disconnect the central VV a wire from an ignition distributor cover.
  1. Establish компрессометр in a candle opening of the first cylinder.
  1. When using a nozzle of clamping type track that diameter of a rubber cone made no more than 20 mm.
  1. Turn the engine at least on seven steps and consider the indication of the measuring instrument. On the serviceable engine pressure has to increase quickly enough. The low pressure on the first step which is followed by its gradual increase on the subsequent speaks about wear of piston rings. If at a further provorachivaniye of a shaft pressure does not rise, it can be regarded as the evidence of leakages of valves or violation of tightness of laying of a head of cylinders (also the probability of existence of cracks in a head is not excluded). The congestion of deposits on working facets of plates of valves can also lead to decrease in compression pressure. Write down the maximum indication of a kompressometr.
  2. Repeat the procedure for the remained engine cylinders. Compare results to standard requirements (see Specifications).
  3. At excessively low results of measurement, fill in in each of cylinders through a candle opening of a little motive oil (two-three teaspoons) and repeat check.

If addition of oil leads to increase in pressure, it speaks about wear of piston rings. If the compression does not increase, leakages of valves or violation of tightness of laying of a head are the reason of its decrease. Leakages of valves can be connected with a burn-out of their saddles, either a deformation / burn-out or mechanical damages of working facets of plates.

If pressure of compression is equally underestimated in two next cylinders, then with high degree of probability it is possible to speak about violation of integrity of laying of a head within its crossing point between these cylinders. Presence of cooling liquid at motive oil will confirm this assumption.

If pressure in one of cylinders is about 20% lower, than in other and it is followed by violation of stability of turns of idling, it is necessary to estimate degree of wear of a cam of the drive of the corresponding final valve on the camshaft.

Unusual overestimate of compression pressure usually is a consequence of an excessive nagaroobrazovaniye in combustion chambers. In this case the head of cylinders has to be removed for the purpose of carrying out decarbonization.

At excessively low results of measurements, and also in case of violation of uniformity of distribution of pressure between cylinders it will be useful to hold testing of the engine for leaks in the conditions of a workshop of car service. Such check will allow to define precisely a source of leak and to estimate degree of its gravity.

Check of the block on leaks

During this check are defined exit speed from cylinders of the compressed air pumped in them and directly the place of leaks. This check is an alternative to check of a compression. Moreover, from many points of view, it is much more effective as visually it is simpler to reveal a leak source, than to comprehend results of measurement of a compression.

The equipment necessary for check on leaks, is not among public therefore performance of this check should be entrusted specialists of the service center.