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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 a head 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 bars.


 PERFORMANCE ORDER

  1. Warm up the engine up to the normal working temperature (about 80 °C), make sure of completeness of a charge of the rechargeable battery.
  2. Kill the engine and allow a final collector to cool down within about 10 minutes.

Petrol models

 PERFORMANCE ORDER

  1. Remove a decorative cover of the engine and disconnect VV an electrical wiring from spark plugs.
  2. Serially turn out spark plugs, - before a reversing of a candle blow its niche compressed air (it is possible to use the bicycle pump) for the purpose of minimization of risk of hit of garbage in cylinders.
  3. Having used a clamping or carving nozzle, connect компрессометр to a candle opening of the first cylinder.
  4. Ask the assistant against the stop having squeezed out the accelerator pedal, to completely open a butterfly valve and to turn the engine a starter on 7-8 turns. Consider the maximum indication of the measuring instrument, write down result.
  5. Working in a similar manner, measure compression pressure in the remained cylinders.
  6. Kill the engine, disconnect компрессометр, screw spark plugs and establish into place a decorative cover of the power unit.

Diesel models

 PERFORMANCE ORDER

  1. Remove tubes of supply of fuel, a nozzle, flat and corrugated washers (see Power supply systems, managements of engine/decrease in toxicity of the fulfilled gases and production of the fulfilled gases).
  2. Disconnect an electrical wiring from the fuel cut-off valve (see Power supply systems, managements of engine/decrease in toxicity of the fulfilled gases and production of the fulfilled gases).

If the valve is not switched-off, TNVD will begin to spray fuel at an engine provorachivaniye!

  1. Suitable cap to a zakuporta returnable fuel-supply line of TNVD.
  1. By means of a transitional nozzle connect the special manometer to a forsunochny opening of the first cylinder.
  1. Having asked the assistant without squeezing out the accelerator pedal several times to turn the engine a starter. Consider the maximum indication of the measuring instrument, write down result.

For obtaining reliable result the engine has to be turned not less than on eight turns.

  1. Working in a similar manner, measure compression pressure in the remained cylinders.
  2. Disconnect компрессометр and return into place the being removed components. Restore initial connection of fuel-supply lines and an electrical wiring, - do not forget to remove a cap from the TNVD returnable line.

All models

Compare results of measurement by requirements of Specifications of the Head Dvigatel.

The most admissible difference of pressure in separate cylinders can make 1.5 kgfs/cm2 for petrol engines and 3.0 kgfs/cm2 for diesel.

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. If pressure does not increase with repetition of cycles, it is necessary to check tightness of closing of valves and integrity of a head of cylinders (also the probability of existence of cracks in a head is not excluded).

Nagaroobrazovaniye on plates of valves can also lead to decrease in compression pressure.

It must be kept in mind that because of the different speed of rotation of a starter the received results on different cars can vary slightly, however indications for all cylinders of one engine have to be approximately identical.

If pressure is in any cylinder at the level of minimum or below admissible, try to pour in the cylinder through a candle opening in a teaspoon of motive oil and repeat check. If addition of oil leads to temporary restoration of a compression, most likely, wear of the piston, piston rings or walls of the cylinder is the reason of its decrease. If increase in a compression did not happen, it is possible to draw a conclusion on violation of tightness of closing of valves or damage of sealing laying / casting of a head of cylinders.

The low compression in two next cylinders with high degree of probability it is identical points to violation of integrity of sealing laying of a head around a crossing point between cylinders. Presence of cooling liquid at cameras a combustion/case of the engine can serve as confirmation to this assumption.

If the compression in one of cylinders is about 20% lower, than in the others, and violation of stability of turns of idling at the same time takes place, it is necessary to estimate degree of wear of working ledges of the corresponding cams of the camshaft.

Check of tightness of cylinders

 PERFORMANCE ORDER

  1. During this check tightness of cylinders is estimated (on the speed of production of the compressed air pumped in them) and, - in case of its violation, - sources of leaks are localized. This check is an alternative to check of compression pressure, and from a certain point of view is much more effective than the last as visually it is simpler to reveal a leak source, than to do theoretical conclusions according to indirect data.
  2. Warm up the engine up to the normal working temperature (80 °C), then muffle it.
  3. Uncover a broad tank of the cooling system (see the Head the Current leaving and service).
  4. Remove a decorative cover of the power unit and turn out ignition/incandescence candles.
  5. 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 to the corresponding candle opening, previously having made its calibration, - act in strict accordance with the instructions attached to the device.
  6. Uncover a jellied mouth of motive oil (see the Head the Current leaving and service).
  7. 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, take care of its blocking.

  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, screw candles of an ignition/incandescence and establish into place a decorative cover of the engine.
  3. Compare results of check with requirements of Specifications of the Head Dvigatel. In case of need make necessary recovery repair.

Check of a condition of mirrors of cylinders by means of a special lamp sampler

 PERFORMANCE ORDER

  1. Remove a decorative cover of the engine and turn out ignition/incandescence candles.
  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, 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, a head of cylinders and make more detailed direct survey of mirrors of cylinders and necessary recovery repair.