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4.1. Check of compression pressure, assessment of a condition of cylinders

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 rather simple to replace sealing laying of a head. Measurement is performed by means of a kompressometr.

For diesel engines it is necessary компрессометр with a limit of measurements approximately to 40 atm.

Warm up the engine up to the normal working temperature (about 80 °C), make sure of completeness of a charge of the rechargeable battery.

Petrol models

For measurement of compression pressure it is necessary to use the measuring instrument equipped with the remote switch of a starter (it is shown on the example of model 202)

01 — Kompressometr
02 — the Remote switch of a starter

8 — the ignition Switch

 PERFORMANCE ORDER

  1. Kill the engine and, according to a complete set, remove assembly of the air cleaner (see the Head of the Power supply system and production of the fulfilled gases).
  2. Serially turn out spark plugs (see the Head Sistemy of electric equipment of the engine).
  3. Take a key from the electronic switch of ignition (EIS).
  4. Prepare equipped with the remote switch of a starter компрессометр
  1. Uncover (1) assembly block of the module of management
  1. Connect a clip (A) of the measuring instrument to the X12/3 plug
  1. Disunite the X35/63 socket and connect to it the adaptor wire (2) equipped with the 6-contact plug, - connect the second end of a wire to a wire of a kompressometr

At measurement of a compression it is not necessary to turn a starter from the ignition switch!

  1. Densely press a measuring instrument nozzle to a bottom of a candle niche of the first cylinder.
  1. Completely open a butterfly valve and, turning the engine the starter activated from the button of the remote switch of a kompressometr consider testimonies of the last. Write down result of measurement.

For removal of a deposit from walls of cylinders the engine should be turned within about 5 seconds.

  1. Working in a similar manner, serially measure compression pressure in the remained engine cylinders.
  2. Kill the engine, disconnect компрессометр, screw spark plugs and install into place the air cleaner.

Diesel models

Check of compression pressure on the diesel models equipped with the series 612 engine

1 — an air distributor Cover
2 — the Overlay of a cover of a head of cylinders
3 — Kompressometr

4 — the Connecting hose
5 — the Carving nozzle
R9 — the Glow plug

Check of compression pressure on the diesel models equipped with the series 628 engine

3 — Kompressometr
5 — the Carving nozzle
6 — Assembly of the air cleaner
7 — the Contact socket

R9 — the Glow plug
Y74 — pressure Valve regulator

 PERFORMANCE ORDER

  1. Kill the engine and uncover the air distributor of a sleeve of a path and an overlay of a cover of a head cylinders/assembly of the air cleaner (see the Head of the Power supply system and production of the fulfilled gases). Turn a key of "ignition" in situation 0.

M612

For measurement of compression pressure it is necessary to use the measuring instrument equipped with the remote switch of a starter (it is shown on the example of model 202)

01 — Kompressometr
02 — the Remote switch of a starter

8 — the ignitions Switch
Y74 — pressure Valve regulator


 PERFORMANCE ORDER

  1. Turn out glow plugs (see the Head Sistemy of electric equipment of the engine).
  2. Prepare equipped with the remote switch of a starter компрессометр.
  1. Uncover (1) blocks of external start (2) and connect a measuring instrument clip to the X4/30 plug
  1. Uncover (arrow) under the dashboard on the right
  1. Take (3) starters which point of installation is noted by S letter from the assembly block of the relay
  1. (S letter on a payment of the assembly block) connect an adaptor wire of a kompressometr to a block (4) relays

At measurement of a compression it is not necessary to turn a starter from the ignitions switch!

  1. By means of a carving nozzle with a flexible connecting hose connect компрессометр to a candle opening of the first cylinder (see the illustration Check of Compression Pressure on the diesel models equipped with the series 612 engine).
  2. Further act according to the instructions provided for petrol engines, - need for squeezing of a pedal gas/opening of a butterfly valve is absent.

For measurement performance the engine has to be turned not less than eight times.


M628

 PERFORMANCE ORDER

  1. Disunite pressure valve regulator socket (see the illustration Check of Compression Pressure on the diesel models equipped with the series 628 engine) and turn out glow plugs (see the Head Sistemy of electric equipment of the engine).
  2. Prepare equipped with the remote switch of a starter компрессометр (see the illustration Check of Compression Pressure on the diesel models equipped with the series 628 engine) and, working further according to instructions (on the example of models 220.028/128 equipped with engines 629.960), connect it to plugs of the corresponding safety lock in the right forward assembly block.
  1. Uncover the right forward assembly block of safety locks and the relay (K40/7) and take a safety lock of maxi (60A) of the fan of the cooling system of the engine from the nest, then disunite the white socket (1)
  1. Connect adaptor wires of a kompressometr to the basic plug (30) of a landing nest of a safety lock (33) and the plug (50) of the white socket (1)

At measurement of a compression it is not necessary to turn a starter from the ignitions switch!

  1. By means of a carving nozzle with a flexible connecting hose connect компрессометр to a candle opening of the first cylinder (see the illustration Check of Compression Pressure on the diesel models equipped with the series 628 engine).
  2. Further act according to the instructions provided for petrol engines, - need for squeezing of a pedal gas/opening of a butterfly valve is absent.

For measurement performance the engine has to be turned not less than eight times.

  1. Alternatively the measurement of compression pressure can be made by means of the diagnostic reader STAR DIAGNOSIS, - act according to the instructions attached to the device.

All models

 PERFORMANCE ORDER

  1. Compare results of measurement by requirements of Specifications.
  2. The most admissible difference of pressure in separate cylinders can make 1.5 atm (for petrol engines) and 3.0 atm (for diesel engines).
  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 signals about that, something valves are untight, or laying of a head of the block is punched (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. It must be kept in mind that because of the different speed of rotation of a starter on different models the results received as a result of measurements can differ. The results received at measurement of a compression have to be approximately identical to all cylinders.
  5. If pressure is in any cylinder at the level of minimum admissible and even below, then for clarification of the reason perform the following operations. Pour in the cylinder through an opening for a candle in a teaspoon of motive oil and repeat measurement of a compression.
  6. 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.
  7. Low compression in two next cylinders almost for certain - 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.
  8. If the compression in one of cylinders is about 20% lower, than in the others, besides turns of idling are unstable, then the reason, perhaps, excessive wear of a cam of the camshaft.
  9. After completion of check establish to the place of a candle, connect to them an electrical wiring, on petrol engines restore initial connection of the coil(s) of ignition. Establish into place a plastic cover of the engine and a safety lock of the fuel pump.

Check of cylinders 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.

All models

 PERFORMANCE ORDER

  1. Warm up the engine up to the normal working temperature (80 °C), then muffle it.

Petrol models

Check of cylinders of petrol engines on leaks


 PERFORMANCE ORDER

  1. Accurately turn the cover (2) of a broad tank (1) of the cooling system equipped with the built-in latch to the first emphasis, wait for dumping of pressure, then turn off a cover finally.
  2. Turn out spark plugs (19).
  3. Turning the engine for the central bolt of a bent shaft in the normal direction, bring the piston of the cylinder which is subject to check into the provision of VMT of the end of a step of compression, then connect a special tester (04) to the corresponding candle opening, previously having made its calibration, - act in strict accordance with the instructions attached to the device.
  4. Uncover a jellied mouth of motive oil (3).
  5. Give compressed air to the cylinder and according to indications of the measuring instrument estimate the speed of dumping of pressure. Write down result.

If during check the bent shaft begins to be turned, block it by means of special adaptation (see the Sections Check and adjustment of basic position of camshafts and Verification of the basic provision of a balancing shaft (only M112 and 628 engines)).

  1. Repeat check for the remained cylinders, - act as ignition (see the Head Sistemy of electric equipment of the engine).
  2. Disconnect the measuring instrument and screw to the place of a spark plug.

Diesel models

Check of cylinders of diesel engines on leaks

 PERFORMANCE ORDER

  1. Turn a cover (1) of a broad tank (2) cooling systems counterclockwise half way, wait for dumping of pressure, then uncover finally.
  2. Remove panels of finishing of the engine (M612)/assembly of the air cleaner (M628).
  3. Turn out glow plugs (R9).
  4. On the models equipped with the series 628 engine remove a pressurization air cooler (see the Head of the Power supply system and production of the fulfilled gases).
  5. On the models equipped with the series 612 engine remove the viscous coupling of the fan of the cooling system (see the Head of the Cooling system, heating, ventilation and air conditioning).
  6. Turning the engine for the central bolt of a bent shaft in the normal direction, bring the piston of the cylinder which is subject to check into the provision of VMT of the end of a step of compression, then connect a special tester (04) to the corresponding candle opening, previously having made its calibration, - act in strict accordance with the instructions attached to the device.
  7. Further affect in the manner similar described above for petrol engines (see paragraphs with 4 on 7 Check of Cylinders points leaks - petrol models).

All models

 PERFORMANCE ORDER

  1. Compare results of check with requirements of Specifications. In case of need make necessary recovery repair.

Check of cylinders by means of a lamp sampler

Petrol models

Check of cylinders of petrol engines by means of a lamp sampler


 PERFORMANCE ORDER

  1. Turn out spark plugs.
  2. Turning the engine in the normal direction for the central bolt of a bent shaft, bring the piston of the cylinder which is subject to check into the provision of NMT.
  3. Working strictly according to instructions of manufacturers, connect a special lamp sampler (05), fill its flexible light guide in the corresponding candle opening and make visual assessment of a condition of walls of the cylinder which have to have an opaque shade without traces of a honingovochny notch.
  4. Working in a similar manner, examine walls of the remained cylinders (as ignition).
  5. In case of need remove the engine, heads of cylinders and make more detailed direct survey of mirrors of cylinders and necessary recovery repair.

Diesel models

 PERFORMANCE ORDER

  1. Take a key of "ignition" from the lock.
  2. Remove panels of finishing of a head of cylinders (M612)/assembly of the air cleaner (M628).
  3. Turn out glow plugs (R9).
  4. Remove nozzles (Y76) (see the Head of the Power supply system and production of the fulfilled gases).
  5. On the models equipped with the series 628 engine remove a pressurization air cooler (see the Head of the Power supply system and production of the fulfilled gases).
  6. On the models equipped with the series 612 engine remove the viscous coupling of the fan of the cooling system (see the Head of the Cooling system, heating, ventilation and air conditioning).
  7. rovorachivy the engine for the central bolt of a bent shaft in the normal direction, bring the piston of the cylinder which is subject to check into the provision of NMT.
  8. Further act in the manner similar described above for petrol engines (see paragraphs with 3 on 5).