Mityvac MV5530 - Mityvac Compression Test Kit Components; Mityvac Compression Test Kit Applications; How to Perform a Compression Test; Compression Test Precautions & Diagnostics

Page Number - 3Form 824255
Always read instructions carefully prior to use.
Included in this Kit
• Heavyduty2¾”(70mm)gaugewithhighimpactlens,
rubberboot,andthree(3)scalesofmeasure(psi,
kg/cm
2
,bar),attachedto10”(250mm)hoseandquick
release coupler
• Four(4)extensionhoses:
• 6½”(165mm)longx14mmthread,short
• 12”(305mm)longx14mmthread,short
• 12”(305mm)longx14mmthread,long
• 12”(305mm)longx18mmthread,short
• One(1)adapter:14mmthread,shortx18mmthread,
long
• Two(2)smallengineadapters
• 10mmthread
• 12mmthread
• One(1)quickreleaseairholdadapter
• Customblow-moldedcase
• Fieldservicekit
Applications
The Mityvac Professional Compression Test Kit can per-
form dry or wet compression tests to determine the amount
of pressure produced in the cylinder of an engine. It can
also be used as a tool for pressurizing an engine cylinder
to hold the valves closed while performing repairs.
How to Perform a Comression Test
Precautions & Diagnostic Notes:
WARNING: DO NOT use the ignition switch during the
compression test on fuel-injected vehicles. Use of a
remote starter switch to crank the engine is recom-
mended. Fuel injectors on many late model vehicles
are triggered by the ignition switch during the cranking
mode, this could result in a re hazard or contamina-
tion of the engine’s oil with fuel.
Always use eye protection when performing compres-
sion tests.
An engine in good operating condition will produce a
certainamountofpressureineachcylinder.Normally,
the cylinders should be within 10 percentage points of
oneanotherandwithinthemanufacturer’sspecications.
The pressure should rise smoothly on each stroke of the
engine,untilitreachesapeak.
Ifthepressurereadingfailstorise,oritremainsthesame
forseveralstrokesoftheengineandbeginstorise,the
likely cause of the problem is a sticking valve.
If two adjacent cylinders show pressure readings of 20 or
morepoundsbelowtheothercylinderreadings,suspecta
blown head gasket.
If a cylinder shows a pressure reading of 15 or more
poundshigherthantheothercylinders,theprobablecause
is carbon build-up inside the cylinder.
The Mityvac Professional Compression Test Kit can
performtwotests:thedrycompressiontestandthewet
compression test. The result of performing these tests will
provideanindicationoftheconditionofthepistonrings,the
cylinders,andvalve-train.
Dry Compression Test Procedures:
1. Refer to the appropriate service manual for the com-
pressionspecicationsspecictotheengineyouare
testing.
2. Start engine and allow engine to run until it reaches nor-
mal operating temperature (usually about 15 minutes.)
TurnengineOFF.
3. Install an auxiliary starter switch in the starting circuit.
4. Whilewearingeyeprotection,usecompressedairto
carefully remove dirt and debris from the area around
the spark plugs.
5. Removesparkplugsoneatatime,markingthenumber
ofthecylindertheywereremovedfrom,andplacethem
onacleanatsurface.Thiswillaidyouinidentifying
problem cylinders by allowing the comparison of spark
plug appearance to the compression level of a given
cylinder.
NOTE: When testing engines with two spark plugs
per cylinder, it is only necessary to remove the
spark plugs located on the exhaust side.
6. Onvehicleswithstandarddistributors,disconnectthe
coil wire (high tension lead) from the distributor cap and
secureittoasuitableground,ordisabletheignitionby
disconnecting the positive (BAT) terminal from the igni-
tion coil.
7. Onvehicleswithadistributorlessignition(DIS),disable
the ignition system by removing the electronic ignition
(control)modulefuse,ordisconnectthecrankangle
sensor.
NOTE: Refer to the appropriate service manual to
determine which fuse or component to temporarily
remove or disconnect.
8. Remove air cleaner from carburetor or throttle body and
securethrottlelinkageinwide-openthrottle(WOT)posi-
tion.
NOTE: NEVER place anything inside the throttle
body; internal damage to the engine could result.
On vehicles equipped with port fuel injection,
remove throttle linkage covers (as necessary) and
secure throttle linkage in the wide-open throttle
(WOT) position.
9. Crank engine several times to ensure removal of any for-