4.3. Diagnostics of a condition of the engine with use of the vacuum gage
Examples of possible indications of the vacuum gage
Vacuum gage use at rather small monetary expenses allows to receive rather capacious information on internal state of the engine. By results of the carried-out measurements it is possible to make idea of degree of wear of piston rings and mirrors of cylinders, to reveal signs of failure of laying of a head of cylinders and the inlet pipeline, violation of adjustments of the carburetor (at the corresponding complete set) and passableness of system of production of the fulfilled gases, jamming or прогара valves, a prosedaniye of klapanny springs, failure of installation of a corner of an advancing of ignition or phases of a gazoraspredeleniye, refusals of system of ignition, etc., etc.
Unfortunately, results of the indications removed by means of the vacuum gage are easily wrong for interpreting, and therefore, they should be analyzed together with the data received during performance of other diagnostic checks.
When reading indications of the indicator of the vacuum gage 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 production show depth of depression in inches of a mercury column. Thus it is necessary to consider that all standard requirements are provided for a case of performance of checks at zero height above sea level. Relief increase on each 300 m after a mark of 600 m leads to understating of instrument readings approximately on 25 mm of mercury.
Connect the vacuum gage 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 starting measurements, warm up the engine to normal working temperature. Prop up wheels protivootkatny boots and cock the parking brake. Transfer transmission to the situation "R", start the engine and leave its working at turns of normal idling.
Before engine start attentively check fan blades on existence of cracks and other damages. Try not to approach to a krylchatka of a hand and a measuring instrument. Also avoid to take a position directly ahead of the car!
Consider vacuum gage indications. On the average depth of depression in the inlet pipeline of the serviceable engine should be rather stable (without arrow breakthroughs) and to make about 430 — 560 mm of mercury. The scheme of interpretation of removed indications is provided in below-mentioned paragraphs (see an illustration Examples of possible indications of the vacuum gage).
Stable low indications can be the certificate of leaks through laying between the inlet pipeline and a head of cylinders, or between the pipeline and the throttle case. The probability of violation of tightness of a vacuum hose, failure of the moment of ignition (towards backlog), or violations of installation of phases of a gazoraspredeleniye is not excluded also. Check installation of a corner of an advancing of ignition by means of a stroboscope, then serially exclude all other possible causes, after it it is meaningful to uncover GRM drive for the purpose of check of correctness of combination of adjusting labels.
If the result of measurement appears on 80 — 200 mm of mercury. lower norms and thus take place fluctuations, violation of tightness of laying of the inlet pipeline near the inlet port, or malfunction of an injector of injection of fuel can appear the reason of such deviation.
Regular deviation of indications down from stable value on 50 — 100 mm of mercury. with high degree of probability testifies to leakages of valves. Check kompressionny pressure in cylinders or carry out the test for leaks.
Irregular deviations and dumpings of indications can appear are connected with jamming of valves or ignition admissions. Measure kompressionny pressure, carry out the test for leaks, check a condition of spark plugs.
Frequent vibration of an arrow of a measuring instrument with amplitude of fluctuations of 100 mm of mercury. at single turns of the engine, being accompanied smoke emission from an exhaust pipe, speaks about wear of directing plugs of valves. Carry out the test for leaks (see. Check of kompressionny pressure in cylinders). If the arrow starts to vibrate at increase of turns of the engine, check on existence of signs of leakages of laying of the inlet pipeline and a head of cylinders. Estimate degree of a prosedaniye of klapanny springs, check on existence of traces прогара valves and try to reveal ignition admissions.
Insignificant fluctuations within a range from 25 to 50 mm of mercury. it is possible to consider as the certificate of violation of serviceability of functioning of system of ignition. Check correctness of all usual adjusting installations, in case of need resort to testing with use of the analyzer of parameters of ignition.
At deviations of indications of a measuring instrument in a wide range check kompressionny pressure or carry out the test for leaks for the purpose of identification of the defective cylinder or violation of tightness of laying of a head of cylinders.
If the arrow of a measuring instrument slowly "walks" in a wide range of a scale, check passableness of system of ventilation of a case (PCV) and structure of a mix of idling, also make sure of absence of leaks through laying of the carburetor / case of a throttle and the inlet pipeline.
Estimate speed of recovery of indications of the vacuum gage when closing butterfly valve after its complete fast opening. The indication at first should fall practically to zero, then rise over value, characteristic for normal turns of idling approximately by 130 mm of mercury. 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 of a butterfly valve, it is necessary to check, whether piston rings are worn-out. At a long delay of return of indications check passableness of system of production of the fulfilled gases (often there is blocked an exhaust silencer or the catalytic converter) — it is simplest to disconnect simply suspected section of system of release and to repeat check.