Mityvac MV5530 - Wet Compression Test Procedure; Small Engine Compression Testing Guide; Using the Pressure Hold Adapter

Page Number - 4 Form 824255
eign matter that may have fallen into the cylinders during
preparation for test.
10.Selecttheappropriateadaptertting(14mm,18mmshort
reachor14mm,18mmlong-reach),andthreadadapter
into spark plug hole of cylinder head.
11. Connect the appropriate test hose or adapter to the
gauge assembly.
12.Cranktheengineatleastvecompressionstrokesor
until the pressure reading stops increasing on gauge.
13. Read the pressure level on the gauge and record the
reading along with the cylinder number being tested.
Example: #1-150 psi, #2-145 psi, etc.
14. Repeat this test on each cylinder. If any of the cylinder
readingsarefoundtobeloworuneven,performwet
compression test.
15.Whencompressiontestiscomplete,returnthespark
plugs to their respective cylinders and the throttle and
ignition components to their normal positions.
Wet Compression Test Procedure
CAUTION: DO NOT perform the wet compression test
on any diesel engine. The higher compression in a
diesel engine may cause engine damage or injury to
the technician.
Thewetcompressionisawaytoremovetheinuenceof
thepistonrings,pistonsandcylindersfromthecompres-
siontest.Aftercompletingthedrycompressiontest,squirt
approximately one teaspoon of engine oil into the spark
plug holes and crank the engine several times to seal the
piston rings. Repeat the dry compression test outlined
above. NOTE: If the readings during the wet compression
testaregreater,thenairisleakingaroundwornordam-
aged piston rings. If the reading is approximately the same
forbothwetanddryteststhenthevalves,valveliftersor
the camshaft lobes are worn. Any low reading of cylinder
compression indicates worn or damaged parts.
Small Engine Compression Testing
The Mityvac Professional Compression Test Kit has two
(2)adapters,10mmand12mm,thatallowittobeusedon
smallenginesfoundinlawnmowers,chainsawsandline
trimmers.Tousetheseadapters:
1. Disconnectthesparkplugwireandremovethespark
plug.
2. Thread the appropriate size adapter onto the compres-
sion tester main hose end until the o-ring seats (do not
use a wrench to tighten).
3. Thread the assembly into the cylinder spark plug hole
untiltheo-ringontheadapterseatsrmly(donotusea
wrench to tighten).
4. Ensure the spark plug is grounded to the cylinder head
or is insulated in a way that will prevent an electric
shock hazard.
5. Crank the engine over using the pull cord (or starter if
electric) a minimum of 5 revolutions. This will allow the
cylindertobuildsufcientcompressiontobemeasured.
6. Refer to the manufacturer’s data to determine the cor-
rect reading
Using the Pressure Hold Adapter
The Mityvac Professional Compression Tester comes with
a pressure hold adapter. This adapter is used to perform
valve seal replacement on an engine without removing the
cylinderhead(s).Tousetheadapter:
1. Remove the spark plug from the desired cylinder.
2. Selecttheappropriateextensionhosethatwilltthe
spark plug hole.
3. Usingthevalvecoretool(fromtheeldservicekitin-
cluded),removethevalvecorefromtheendofthehose
and lay it aside.
4. Thread the extension hose into the spark plug hole
until the o-ring seats; do not use pliers or a wrench to
tighten.
5. Attach the Air Hold Adapter to the extension hose.
6. AttachashopairhosetotheAirHoldAdapter,thiswill
maintain air pressure in the cylinder to hold the valves
closed while performing repairs. (It may be necessary
to rotate the engine until all valve are closed and air is
holding in the cylinder)
Note: Air Hold quick connector does not come with a
compressed air line tting to adapt to your air source.
This will have to be purchased separately to t your
system.
Contacting Lincoln Industrial Corp.
LincolnIndustrialCorporation,
OneLincolnWay,
St.Louis,MO63120
Phone:(314)679-4200Ext.4410
Fax:(800)424-5359
E-mail:custserv@lincolnindustrial.com
Fortechnicalquestions,pleasecontactourTechnicalSer-
viceDepartment:
Phone:(314)679-4200Ext4782
Fax:(314)679-HELP(4357)
E-mail:techserv@lincolnindustrial.com
VisitourWebSiteat:www.mityvac.com
TO AVOID PERSONAL INJURY AND/OR VEHICLE DAM-
AGE:
Whilesomeprecautionsarespeciedinthismanual,
and should be noted to avoid personal injury or vehicle