Mityvac 05530 COMPRESSION TEST KIT - Manual (Page 3)

Page Number - 3 Form 823541
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
perform 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 perform-
ing 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 fire 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 specifica-
tions. 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
compression specifications specific to the engine you
are testing.
2. Start engine and allow engine to run until it reaches
normal 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 flat surface. This will aid you in
identifying problem cylinders by allowing the compari-
son 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 ignition 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) position.
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.