"Gazelle" Gas-2705>> The engine>> Engines ZMZ-4025,-4026>> Diagnostics of a technical condition of the engine and its possible malfunctions
The technical condition of the engine while in service constantly changes. During the period обкатки (about 2000 km) on a measure extra earnings of rubbing surfaces decrease losses on a friction, increases capacity of the engine, decreases the fuel expense, the oil charcoal fumes decrease. Further there comes the period at which the technical condition practically changes a little. In process of deterioration of details break of gases through piston rings increases, the compression in cylinders falls, oil leak through backlashes in connections increases and pressure in system falls. Hence, capacity of the engine gradually decreases, the fuel expense increases, the oil expense increases.
Definition of a technical condition of the engine for timely regenerative repair rather important. It will prolong the general service life of the engine and will warn an engine emergency exit out of operation.
The engine condition is estimated on indicators of devices (temperature of a cooling liquid and pressure of oil), to an engine kind of work on various modes (uniformity, to noise qualities), on compression size in cylinders of the engine, reaction of the car to change of giving of fuel by an accelerator pedal.
Falling of capacity of the engine is shown in decrease in dynamic qualities of the car, in deterioration приемистости. The car is inertly dispersed, hardly overcomes lifting (it is necessary to include prematurely lowering transfer), does not develop the maximum speed. It is necessary to mean that the specified signs can be also a consequence of infringement of adjustment of mechanisms of a running gear of the car.
The way free качения (выбег) the serviceable car, with full loading, moving with a speed of 50 km/h, should be not less than 550 m. Such test is spent to windless weather on a dry horizontal site of highway with an asphalt or concrete covering.
The expense of fuel (operational) depends not only on a technical condition of the engine, but also (at a working order of a running gear of the car) from road conditions, loading, driving methods, therefore the operational expense of fuel is not an objective indicator of a technical condition of the engine.
The technical condition of the engine (at serviceability of other mechanisms of the car) is defined by the control expense of fuel at movement completely груженного the car on a horizontal site of highway with an asphalt or concrete covering with a speed of 60 km/h. Test is spent on a site by extent of 4-5 km in two opposite directions. The control expense for обкатанного the car should not exceed 11 l on 100 km. At definition of the control expense of gasoline use a separate measured tank.
Check of a compression (pressure) in cylinders in the end of a compression step is made компрессометром. Before measurement it is necessary to check up correctness of thermal backlashes in valves and if necessary to adjust. A compression in cylinders measure on heated-up till 70-85 C the engine at completely open throttle заслонке the carburettor and the turned out candles, the carburettor thus should be without fuel.
The rubber tip компрессометра is inserted into an aperture of a candle of the first cylinder, providing consolidation on an aperture edge, and the cranked shaft of the engine is scrolled by a starter until pressure in the cylinder will not cease to increase (but no more than 10-15 seconds). The storage battery should be serviceable and completely charged.
The compression in cylinders for the engine 4026 less than 850 кПа (8,5 kgs/sm 2) and for the engine 4025 less than 800 кПа (8 kgs/sm 2) testifies to deterioration or malfunction of piston rings or about негерметичности landings of valves. To establish a true cause of defect, it is necessary to fill in through a candle aperture in each cylinder on 20—30 sm of 3 oils, applied to the engine, and again to check up a compression. Compression increase specifies in malfunction (deterioration) of rings or the cylinder; if value of a compression has not raised, tightness of landing of valves, hence, is broken.
The expense of oil on charcoal fumes is supervised by gauging of quantity of the oil added to a label П of the index of level, for certain run. Gradually, in process of increase in deterioration of details of the engine, the oil expense increases. If the expense of oil on charcoal fumes exceeds 0,25 l on 100 km the engine is subject to repair.
Pressure of oil in system is checked by a control manometre which joins the oil filter instead of the gauge of pressure of oil (a carving in the filter 1/4 conic). Pressure of oil less than 100 кПа (1 kgs/sm 2) on the heated-up engine at average frequency of rotation and less than 50 кПа (0,5 kgs/sm 2) at small frequency of idling testifies to malfunctions in system of greasing or excessive deterioration of bearings cranked or a camshaft. Such engine is subject to repair.
Шумность engine works it is checked by listening of its work idling at various frequency of rotation of a cranked shaft. The engine should be heated-up to temperature 70—85 With.
Without stethoscope application listen to work газораспределительного the mechanism: valves — at frequency of rotation of 600-1200 mines-1, pushers — at frequency of rotation of 1000-1500 mines-1, camshaft gear wheels — at frequency of rotation of 1000-2000 mines-1. By means of a stethoscope listen to work of piston group, шатунных and radical bearings at sharp short-term increase of frequency rotation of a cranked shaft to 2500 mines-1.
Knock and tinkling sound of pistons, piston rings, knock шатунных the bearings, listened by a stethoscope are not supposed; allocated knock of piston fingers, radical bearings, knock or sharp noise of a high-pitch tone of distributive gear wheels, sharp allocated knock of valves and pushers, sharp knock and noise of a high-pitch tone of gear wheels of the oil pump and its drive, noise of a high-pitch tone and peep крыльчатки and the bearing of the pump of the cooling liquid, listened without a stethoscope. Uniform knock of valves and the pushers, merging in the general noise are supposed; periodic knock of valves and pushers at normal backlashes in клапанном the mechanism; allocated knock of valves and the pushers, disappearing or appearing at sharp change of frequency of rotation of a cranked shaft of the engine; equal unsharp noise of gear wheels of a drive of a camshaft and noise of gear wheels of the oil pump not allocated from the general background and its drive.
During car operation there can be various malfunctions of the engine for which elimination it is not required car deliveries in special repair shop. On engine work at sufficient skill it is possible to judge its technical condition. On hearing the increased backlashes in interfaces, casual breakages and easing of fixing details can be revealed. Having found out while in service any malfunction in engine work, it is necessary not to hurry up to assort the engine, and to try to establish a cause of defect before dismantling.
Engine dismantling start, having convinced of the valid necessity of this operation. Even partial dismantling of the engine breaks, as a rule, consolidations, to extra earnings of the interfaced details and increases their deterioration at the subsequent operation.