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Idiomas disponibles
Idiomas disponibles
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 tem-
perature (usually about 15 minutes )
Turn engine OFF
3 Install an auxiliary starter switch in the
starting circuit
4 While wearing eye protection, use com-
pressed 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 comparison of spark plug appear-
ance 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
9 Crank engine several times to ensure
removal of any foreign matter that may
have fallen into the cylinders during
preparation for test
10 Select the appropriate test adapter and
thread it into the spark plug hole of
cylinder 1 until the o-ring on the adapter
seats firmly (do not tighten with a
wrench)
11 If required, thread a test adapter with a
hose onto the installed adapter until the
o-ring seats firmly (do not tighten with a
wrench)
12 Connect the test gauge to the opposite
end of the test adapter hose
13 Turn the tester on by pressing the ON/
UNIT/OFF button
14 Press and hold the CYLINDER button for
at least three (3) seconds to clear the
memory and return the cylinder indica-
tor to "CYL# 1"
15 While watching the test gauge, crank the
engine as least five (5) compression
strokes or until the pressure reading
stops increasing (the peak compression
value will automatically be stored in
memory)
16 Relieve the pressure in the tester by
pressing the pressure relief button
17 Disconnect the gauge and remove the
test adapter(s) from cylinder 1
18 Install the test adapter(s) into cylinder 2
and reconnect the gauge
19 Advance the cylinder number shown on
the tester LCD to 2 by pressing the
CYLINDER button
20 Repeat the compression test on cylinder
2 and all remaining cylinders Be sure to
advance the cylinder number on the
tester for each cylinder
21 After testing all cylinders, review the
values of each cylinder by pressing the
CYLINDER button to scroll through the
results
8
22 If any of the cylinder readings are found
to be low or uneven, perform wet com-
pression test
23 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
The wet compression test is a way to remove
the influence of worn piston rings, pistons
and cylinders from the compression 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 compres-
sion test are greater, then air is leaking
around worn or damaged 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 cyl-
inder compression indicates worn or
damaged parts
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