4.3. Diagnostics of a condition of the engine with vacuum gauge application
Examples of possible indications of the vacuum gauge
Vacuum gauge use at rather small monetary expenses allows to receive capacious enough information on inwardness of the engine. By results of the spent measurements it is possible to make representation about degree of deterioration of piston rings and mirrors of cylinders, to reveal signs of failure of linings of a head of cylinders and the inlet pipeline, infringement of adjustments of the carburettor (at a corresponding complete set) and passableness of system of release of the fulfilled gases, jamming or прогара valves, проседания клапанных springs, failure of installation of a corner of an advancing of ignition or phases timing, refusals of system of ignition, etc., etc.
Unfortunately, results of the indications removed by means of the vacuum gauge are easily wrong for interpreting, that is why, they should be analyzed together with the data received during performance of other diagnostic checks.
At reading of indications of the indicator of the vacuum gauge it is necessary to pay attention not only to absolute size of a deviation of an arrow, but also for speed of its moving. The majority of measuring instruments of import manufacture show depth of depression in inches of a mercury column. Thus it is necessary to consider that all standard requirements are resulted for a case of performance of checks at zero height above sea level. Relief increase on each 300 m after a mark in 600 m leads to understating of instrument readings approximately on 25 mm hg
Connect the vacuum gauge directly to the inlet pipeline — not to the throttle case. Track, that during check performance all hoses remained connected, otherwise it will be impossible to consider the read instrument authentic.
Before to start measurements, warm up the engine to normal working temperature. Prop up wheels противооткатными boots and cock a lay brake. Translate transmission in position «Р», start the engine and leave its working on turns of normal idling.
Before engine start attentively check up fan blades on presence of cracks and other damages. Try not to approach to крыльчатке hands and a measuring instrument. Also avoid to take of a position directly ahead of the car!
Consider vacuum gauge indications. On the average depth of depression in the inlet pipeline of the serviceable engine should be enough stable (without arrow jerks) and to make about 430—560 mm hg In below-mentioned paragraphs the scheme of interpretation of removed indications (Examples of possible indications of the vacuum gauge see an illustration) is resulted.
Stable low indications can be the certificate of leaks through a lining between the inlet pipeline and a head of cylinders, or between the pipeline and the throttle case. The probability of infringement of tightness of a vacuum hose, failure of the moment of ignition (towards backlog), or infringements of installation of phases timing is not excluded also. Check up installation of a corner of an advancing of ignition by means of a stroboscope, then serially exclude all other possible reasons, only after that it makes sense to uncover drive ГРМ for the purpose of check of correctness of combination of adjusting labels.
If the result of measurement appears on 80—200 mm hg below norm and thus fluctuations take place, infringement of tightness of a lining of the inlet pipeline around inlet port, or malfunction of an injector of injection of fuel can appear the reason of such deviation.
The regular deviation of indications downwards from stable value on 50—100 mm hg with high degree of probability testifies to leaks of valves. Check up компрессионное pressure in cylinders or carry out the test for leaks.
Irregular deviations and dumps of indications can appear are connected with jamming of valves or ignition admissions. Measure компрессионное pressure, carry out the test for leaks, check up a condition of spark plugs.
Frequent vibration of an arrow of a measuring instrument with amplitude of fluctuations of 100 mm hg at single turns of the engine, accompanied by smoke emission from an exhaust pipe, speaks about deterioration of directing plugs of valves. Carry out the test for leaks (Check компрессионного pressure in cylinders see). If the arrow starts to vibrate at increase of turns of the engine, check up on presence of signs of leaks of a lining of the inlet pipeline and a head of cylinders. Estimate degree проседания клапанных springs, check up on presence of traces прогара valves and try to reveal ignition admissions.
Insignificant fluctuations within a range from 25 to 50 mm hg can be considered as the certificate of infringement of serviceability of functioning of system of ignition. Check up correctness of all usual adjusting installations, in case of need resort to testing with application of the analyzer of parametres of ignition.
At deviations of indications of a measuring instrument in a wide range check up компрессионное pressure or carry out the test for leaks for the purpose of revealing of the defective cylinder or infringement of tightness of a lining of a head of cylinders.
If the arrow of a measuring instrument slowly "walks" in a wide range of a scale, check up passableness of system of ventilation картера (PCV) and structure of a mix of idling, also make sure of absence of leaks through linings of the carburettor / of the case of a throttle and the inlet pipeline.
Estimate speed of restoration of indications of the vacuum gauge at closing throttle заслонки after full its fast opening. The indication at first should fall practically to zero, then rise over value, characteristic for normal turns of idling approximately on 130 mm hg and again to return to the indication of single turns. If depth of depression is restored slowly and does not form a peak throw at sharp closing throttle заслонки, it is necessary to check up, whether piston rings are worn out. At a long delay of return of indications check up passableness of system of release of the fulfilled gases (often appear blocked the muffler or каталитический the converter) — most easier simply to disconnect suspected section of system of release and to repeat check.