Equus 3614 - Compression Tester Plus (6-piece kit) - Manual (Page 2)

ABOUT THIS TOOL
The compression tester is a diagnostic tool which can help you
identify worn or damaged pistons, rings, valves and gaskets. A
compression check consists of measuring pressure at each
cylinder at cranking speed. ALWAYS perform a compression
check as part of the tune-up procedure.
TEST PROCEDURES
CAUTION: Engine parts and surrounding areas will be hot.
1. Stop engine. Carefully disconnect all spark plug wires
from spark plugs. Number spark plug wires to aid in
proper reinstallation.
NOTE: To prevent damage to spark plug wires, be
sure to disconnect wires by first twisting then pulling on
the wire's boot and not on the wire itself.
2. Remove all spark plugs and place in order
corresponding to the cylinders from which they were
removed. (This procedure is used to associate cylinder
or compression problems by inspecting the condition
of a malfunctioning cylinder's spark plug.)
NOTE: To prevent thread damage on vehicles with
aluminum heads, wait approximately ten minutes before
removing spark plugs.
3. Locate the intake throttle plate (or carburetor throttle
plate). Secure the plate wide open for testing.
NOTE: You may also have an assistant help you by
holding the accelerator pedal down.
CAUTION: Be sure to return the throttle plate to it's origi-
nal (closed) position after testing or before starting ve-
hicle. Failure to comply can result in serious engine
damage.
4. Disable the ignition system:
NOTE: These are typical ignition systems. Refer to
your vehicle's service manual for additional information
on your vehicles ignition system and how to safely
disable it.
For electronic or conven-
tional breaker point ignition
systems: Remove the high
tension (coil) wire from the
distributor cap and connect to
a known good ground to avoid
spark discharge, or disconnect
coil primary connector.
For General Motors HEI
systems: Disconnect the
primary (or battery) con-
nection from the distributor
cap and wrap with tape to
avoid accidental grouding.
5. Disconnect the spark plug hose from the compression
gauge. Screw the plug end of the hose into the spark
plug hole. HAND TIGHTEN ONLY.
NOTE: On engines with 14MM long
reach plugs, use the 14 MM
long reach adapter
included in kit. DO
NOT use adapter
in short reach
holes – it may hit
the top of the pis-
ton and damage the
engine.
6. Connect the spark plug hose to
the compression gauge by
means of the "quick connect"
coupling. Make sure the coupling snaps into place.
This ensures the hose is "locked" into the gauge.
7. Crank the engine for at least
five compression strokes.
NOTE: Engine should be
cranked the same number of
strokes for each cylinder.
8. Record the reading from the
compression gauge for
reference. Press the side
release valve to release
pressure from the gauge.
Disconnect the spark plug
hose from the compression
gauge. Connect the hose to
the next cylinder, and repeat
steps 5 through 8 (repeat for
each cylinder to be tested).
COMPRESSION TESTER
30
60
90
120 150 180
210
240
270
300
0
2
4
6 8 10 12
14
16
18
20
kPa x 100
PSI 0 IEC
COMPRESSION
TESTER
30
60
90
120
150
180
210
240
270
300
0
2
4
6
8 10 12
14
16
18
20
kPa x 100
PSI
0
IEC
RELEASE
VALVE
SAFETY TIPS
1. Always wear safety eye protection.
2. Put transmission in “park” (for automatic) or “neutral”
(for manual). Set parking brake and block drive wheels.
3. Be sure to disable the ignition system to prevent the
car from starting (see TEST PROCEDURES, step 4).
4. This compression tester is designed for use on spark-
ignited gasoline engines which do not exceed 250 psi. Use
of this tool for any other purpose may result in personal
injury, damage to the tool, or damage to your vehicle.
BEFORE TESTING
To ensure that compression readings are accurate,
perform the following pre-test procedures.
1. Make sure the vehicle battery is fully charged, and the
starter system is in good condition.
2. Warm up the engine until normal operating temper-
ature is reached.
3. Be sure to remove ALL spark plugs before performing
the compression test.
4. On carbureted models, open choke plate to allow air
flow through the carburetor during testing (see TEST
PROCEDURES, step 3).
HIGH TENSION
LEAD
CHASSIS GROUND
PRIMARY
WIRE
READING TEST RESULTS
The compression check identifies variations in com-
pression between cylinders. Compression is considered
normal if the lowest compression reading is at least 75%
of the highest reading, as shown in the following example:
Cylinder Cyl 1 Cyl 2 Cyl 3 Cyl 4 Cyl 5 Cyl 6
Reading 130 125 140 125 130 115
(psi)