Page Number - 4
Form 823451
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 influence of the
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 compression 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 cylinder
compression indicates worn or damaged parts.
Small Engine Compression Testing
The Craftsman 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 compression
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 firmly (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 sufficient compression to be measured.
6. Refer to the manufacturer’s data to determine the correct
reading
Using the Pressure Hold Adapter
The Craftsman 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 fit the spark
plug hole.
3. Using the valve core tool (from the field service kit included),
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: The air hold quick connector does not come with
a compressed air line fitting to adapt to your air source.
This will have to be purchased separately to fit your
s y s t e m .
For answers to technical questions, or to
order replacement parts, call or fax:
Phone: (314) 679-4200 Ext. 4782
Fax: (314) 679-HELP (4357)
Full One Year Warranty
If this Craftsman® Compression Test Kit is defective in material or
workmanship within one (1) year from the date of purchase,
return it to your nearest Sears store in the United States, and it will
be replaced free of charge.
Sear, Roebuck and Co., Dept. 817WA,
Hoffman Estates, IL 60179
TO AVOID PERSONAL INJURY AND/OR VEHICLE
DAMAGE:
While some precautions are specified in this manual, and
should be noted to avoid personal injury or vehicle damage,
it is not possible for these cautions to cover all conceivable
ways in which service or testing might be done, or all
possible hazardous consequences of each way, nor could
Lincoln possibly know or investigate all such ways. It is
therefore the responsibility of anyone using this manual or
any other Mityvac product, to satisfy him or herself
completely that neither personal safety nor vehicle safety
will be jeopardized by the service methods selected. Any
such injury or damage is entirely the user’s responsibility.
This device is not to be used in any manner on the human
body.
