Sealey VSE3157 Uživatelský manuál stáhnout pdf (Strana 2)

VSE3157 Issue No: 1 - 15/12/10

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Original Language Version

3.1. Overview of compression testing.

 Whenanengine’sperformanceisdown,orifmisringoccurswhichcannotbeattributedtotheignitionorfuelsystems,acompression

test can provide diagnostic clues as to the engine’s condition.

 Compressionshouldbuildupquicklyinahealthyengine.Averylowcompressionreadingontherststroke,followedbygradually

 increasingpressureonsuccessivestrokes,indicateswornpistonrings.Alowcompressionreadingontherststroke,whichdoesnot

build up during successive strokes, indicates leaking valves or a faulty head gasket (a cracked head could also be the cause).

Deposits on the undersides of the valve heads can also cause low compression. If the pressure in any cylinder is considerably lower than

the others, introduce a small quantity of clean oil into that cylinder through the glow plug hole, and repeat the test. If the addition of oil

temporarily improves the compression pressure, this indicates that bore or piston wear is responsible for the pressure loss. If there is no

improvement, it suggests that the leakage is around the valves, or a faulty head gasket. A low reading from two adjacent cylinders

 suggestsafaultyheadgasketbetweenthetwocylinders.Thepresenceofcoolantintheengineoilwillconrmthis.

If the compression is unusually high, the combustion chambers are probably coated with carbon deposits. If this is the case, the cylinder

head should be removed and de-carbonised.

As a rough guide, engines having a compression pressure in excess of 100psi (6.9 bar), should not exceed a compression loss of more

than 10psi (0.69 bar). On older engines with lower compression pressure, loss should not exceed 0.35 bar (5psi).

3.2. Compression Testing.

3.2.1. Check the engine oil is at the correct level.

3.2.2. Remove all of the glow plugs from the engine.

3.2.3. Selecttheapplicableadaptorfromoneoftheaccompanyingkitsandscrewitintotherstglowplugport,ensuringthereisagoodseal

 withtheO-ring(iftted).Connectthecouplingonthepressuregaugehosetotheadaptor,ensuringitlocksintoplace.

3.2.4. Turn over the engine using the starter motor and observe the gauge, looking for a steady increase in the reading (see 3.1) and note the

maximum reading obtained. Refer to the vehicle/engine manufacturer’s workshop manual for compression results data.

3.2.5. Depress the Re-set Valve (situated under the gauge) to release the pressure. The Re-set Valve allows the test to be repeated if required

without disconnecting the tester from the glow plug port.

WARNING! Always release pressure via the Re-set Valve BEFORE disconnecting the Tester.

3.2.6. Disconnect the compression tester from the adaptor and remove the adaptor from the glow plug port. Install them into the next cylinder’s

glow plug port and repeat the tests. Continue the tests for all of the remaining cylinders in turn.

NOTE: A variation in compression readings between cylinders is often a better indication of engine problems than the individual values of

compression.

3.3. TDC Indicator Tool.

3.3.1. Remove the glow plug from cylinder number 1. It may also be necessary to remove all glow plugs to facilitate manual turning over of the

engine.

3.3.2. Select the applicable adaptor from one of the accompanying kits and screw it into the glow plug port of cylinder number 1. Ensure that

 thereisagoodsealwiththeO-ring(iftted).ConnectthecouplingontheTDCndertotheadaptor,ensuringitlocksintoplace.

3.3.3. Position the indicator in a vertical position, in a suitable viewable location, using the magnetic hook if needed.

3.3.4. Turn the engine over manually, using a spanner or socket on the crankshaft pulley, in the direction of engine rotation and watch for the

 oattoriseinthetube.Asthepistonrisesonthecompressionstroke,theoatwillrisetothetopofthetubeandstaythere,whenthe

 pistongoespastTDCandcompressionislost,theoatwillsuddenlysink.Notepositionandtemporarilymakesuitablemarkstoindicate

TDC, or compare with existing timing marks.

3.3.5. Turntheengineoverafurther1¾turnsandtheoatshouldstarttoriseagainasthepistonrisesonthecompressionstroke.Continue

 toslowlyturnthecrankshafttowardsTDC(watchingthetimingmarks)-notetheexactpointwhentheoatdrops.Alterthetimingmarkif

required.

3.3.6. Repeat the procedure, turning the engine over a further 2 turns to re-check for accuracy.

3.3.7. Disconnect the TDC tool from the adaptor and remove the adaptor from the glow plug port.

3. INSTRUCTIONS

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