4.4. Diagnostics of the engine by means of the vacuum gauge, check of a compression and dismantle of the power unit (security measure)

Depression measurement is reliable and rather cheap way of diagnostics of the engine. Under vacuum gauge indications it is possible to receive representation about a condition of piston group, about tightness of linings of a head of the block of the cylinders which are soaking up and final collectors, correctness of adjustments of the power supply system of the engine and release of the fulfilled gases, throughput of the fulfilled gases, a condition of valves (them залипании or a burn-out) and springs of valves and also to check up correctness of adjustment of the moment of ignition and preservation of phases газораспределения at engine work.

Unfortunately, vacuum gauge indications are difficult for interpreting and results of the analysis of indications can be erroneous, therefore, vacuum diagnostics expediently to unite with other methods.

Initial factors on which indications of the vacuum gauge are analyzed and the most exact conclusions about an engine condition become, the absolute instrument reading and character of movement of an arrow of the device (dynamics of indications) are. A scale of the majority of vacuum gauges проградуирована in mm. рт. A column. In process of depression increase (and accordingly pressure drop) the instrument reading increases. On each 300 m above sea level absolute indications of the vacuum gauge will differ approximately on 25 мм.рт.ст.

Attach вакууметр directly to a soaking up collector (the photo See), but not to other apertures through which the vacuum, by the channel of certain length separated from a collector (for example, to apertures before throttle заслонкой) is created.

Before the beginning of tests completely warm up the engine. Block wheels and put the car on a manual brake. At position of the lever of a gear change in neutral position (or in position Park on cars with automatic transmission) start the engine and leave to idle.

Check up the vacuum gauge indication. On the serviceable engine the vacuum gauge should show depression 430 - 560 мм.рттст., and the arrow of the device should be practically motionless.

More low the description of character of indications of the vacuum gauge and a technique of definition of a condition of the engine on their basis follows.

1. Too low level of depression usually specifies on not tightness of a lining between ' a soaking up collector and the chamber throttle заслонки, a vacuum hose, and also in too later ignition or for the wrong moment of opening and closing of valves. Before removing covers of a gear belt and to check up combination of adjusting labels check up installation of ignition by means of a stroboscope and eliminate all other possible reasons, being guided by the techniques of check described in the present Chapter.

2.  If  vacuum gauge indications  on 75 - 200 мм.рт.ст. Below normal also are unstable (the arrow twitches) it specifies in a leak in a lining on an input of a soaking up collector or on malfunction of an atomizer.

3. If the arrow regularly deviates on 50 - 100 мм.рт.ст., the reason is not tightness of valves. For acknowledgement of this conclusion check up a compression in engine cylinders.

4. The arrow irregularly deviates towards low indications, or shaking shows low depression. The probable reason is the raised resistance to movement of valves, or faults in work of cylinders. Check up a compression in cylinders and examine candles.

5. If idling the arrow quickly fluctuates within 100 мм.рт.ст., and engine work is accompanied by a smoke from the muffler directing plugs of valves are worn out. For check of this conclusion it is necessary to conduct tests of chambers of combustion for tightness (with air rating). If the arrow quickly fluctuates and  the increase in turns of the engine it is necessary to check up tightness of a lining of a soaking up collector, elasticity of springs of valves is simultaneously observed. Such indications also can be caused a burn-out of valves and faults in work of cylinders (ignition failures).

6. (Within 20-30 мм.рт.ст.в both parties) specify weak fluctuations of an arrow in unstable work of ignition. Check up all provided installations and adjustments, if necessary connect to the engine the analyzer of system of ignition.

7.  At the big fluctuations of an arrow check up a compression in cylinders, or conduct tests for tightness as causes of defect can be the idle cylinder, or infringement of tightness of a lining of a head of cylinders.

8. If instrument readings slowly vary in a wide range check up cleanliness of pipelines of system of compulsory ventilation картера, correctness of adjustment of a gas mixture, tightness of linings of the case throttle заслонки, or a soaking up collector.

9. Sharply open throttle заслонку and when engine turns will reach 2500 rpm release заслонку. Заслонка should come back slowly in a starting position. Vacuum gauge indications should fall almost to zero, then increase and exceed the control indications corresponding to stationary idling approximately on 125 мм.рт.ст., then depression should be restored at former level. If depression is restored slowly, and at sharp opening заслонки excess of the control indication is absent, the reason deterioration of piston rings can be. At the slowest restoration of depression check up cleanliness of a final path (as a rule the muffler or каталитического the converter). The most simple way of such check consists in disconnection of an exhaust path before a suspicious site and in test repetition.

3.6 More preferable is application of a rolled measuring instrument of a compression in comparison with those devices which for tightness maintenance at measurement nestle by hand. Be convinced, that throttle заслонка it is fixed in completely open position

1. Results of check of a compression in engine cylinders allow to judge a condition of group of details in the top part of the engine (pistons, rings, valves and a lining of a head of the block of cylinders). Namely, compression reduction can be caused негерметичностью chambers of combustion owing to deterioration of piston rings, damage of heads of valves and saddles, прогара linings of a head of the block of cylinders.

2. Begin that clear sites near to spark plugs for what blow compressed air (in the absence of the compressor blow sites automobile, or even bicycle, the pump). It is necessary  to exclude dirt hit in cylinders at compression measurement.

3. Turn out spark plugs (see Гл.1).

4. Completely open throttle заслонку and fix in such position.

5. Disconnect the central high-voltage wire from a cover of the distributor of ignition, connect it to weight on the block of cylinders. For reliability connection with weight execute by means of a special short-circuiting piece of a wire with clips of alligator type on both ends. Also will not prevent to remove a safety lock of electronic system of injection of fuel on the assembly block that will provide

Full switching-off of the electric fuel pump at compression measurement.

6. Insert a compression measuring instrument into an aperture for a candle.

7. Include a starter and turn коленвал on some turns, watching for indications of a manometre of a measuring instrument of a compression. On the serviceable engine pressure should accrue quickly. Low pressure after the first course of the piston and slow increase at the subsequent steps of compression specifies in deterioration of a piston track. If after the first course of the piston pressure low, and at the subsequent steps of compression does not increase, the reason is leak in valves or негерметичность linings of a head of the block of cylinders [the reason formation of cracks in a head) also can be. Compression decrease can be caused also deposit adjournment on heads of valves. Write down the greatest value of a compression.

8. Repeat procedure of measurement for other cylinders, results compare to standard data.

9. Through an aperture for a candle enter into each cylinder of a few oil for the engine (about three full шприцевых butterdishes), then repeat tests.

10. If after introduction of oil the compression has raised, it is possible to draw an unequivocal conclusion that piston rings are worn out. If the compression increases slightly leak occurs through valves, or a lining of a head of the block of cylinders. Leak through valves can be caused a burn-out of saddles and-or facets of valves, and also deformation of cores of valves, or formation on them of cracks.

11. If a compression equally low only in two next cylinders the most probable reason is the lining burn-out between these cylinders. Occurrence in chambers of combustion or in картере коленвала the block of cylinders of traces of a cooling liquid will be acknowledgement of this conclusion.

12. If value of a compression in one of cylinders more low for 20 percent, than in other cylinders and the engine unstably idles, deterioration of a cam raspre-dvala, operating the final valve can be the reason.

13. If value of a compression exceeds norm the combustion chamber is covered by deposit adjournment. In this case a head of cylinders it is necessary to remove and remove a deposit.

14. If the compression in all cylinders low, or strongly differs for different cylinders it is necessary to conduct tests of chambers of combustion for tightness for what it is necessary to address in a specialised workshop. As a result of tests places of leaks should be precisely established and the quantitative characteristic of leak is given.

If the decision on dismantle of the engine for major repairs carrying out, or repair of the basic knots it is necessary to spend certain preparatory measures was accepted.

Will plan extremely important a place in which to be made works. Undoubtedly, best place is the workshop. It is very important to have the equipped working platform, and also a place for car storage. If neither a workshop, nor the garage is not present, the equal and pure concrete or asphalted platform is required at least.

Washing of a motor compartment and the power unit before the dismantle beginning will allow to keep the tool clean and a constant working condition.

Also will be necessary the floor lift or тельфер. Be convinced that these devices have a stock on load-carrying capacity and are capable to lift the engine with transmission. Observance of security measures here plays a paramount role, as lifting of the engine from the car - operation potentially dangerous.

If works on engine dismantle are spent by not skilled person the assistant is necessary. Consult and ask to help the persons having experience in such works. There is a set of examples of that as attempts alone to execute dismantle of the engine with lifting of last of a motor compartment came to an end unsuccessfully.

In advance plan the actions. Before beginning works hire or get all necessary tools and the equipment. To some adaptations providing safety at dismantle and installation of the engine, and also

Decrease in expenditures of labour concern (besides the lift) a jack-cart of the sufficient load-carrying capacity, a full set of keys and оправок, wooden колодки, rags and solvent for cleaning of inevitable pools from the spilt working liquids of the engine. If the lift is hired, about it agree in advance, having performed all works in which this mechanism is not required. It will allow to save money and time.

Keep in mind, that considerable time you cannot take advantage of the car. For performance of some works inaccessible in house conditions in the absence of the special equipment, it is necessary to address in a car-care centre workshop. These enterprises work under the schedule and expedient will consult there before engine dismantle precisely to estimate expenses of time for repair and restoration of details.

Always at dismantle and installation of the power unit be very attentive. Rash actions can cause serious traumas. In advance consider the actions. Do not regret on it time, for the main thing - work without traumas.