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Compression Testing Kit
Model Number: CHT692
Part Number: 1801692
GUARANTEE
This product is guaranteed against faulty
manufacture for a period of 12 months from the
date of purchase. Please keep your receipt
which will be required as proof of purchase.
This guarantee is invalid if the product is found to
have been abused or tampered with in any way,
or not used for the purpose for which it was
intended.
Faulty goods should be returned to their place of
purchase, no product can be returned to us
without prior permission.
This guarantee does not effect your statutory
rights.
SAFETY
WARNING: THE WARNINGS, CAUTIONS AND
INSTRUCTIONS DISCUSSED IN THIS MANUAL
CANNOT COVER ALL POSSIBLE CONDITIONS
AND SITUATIONS THAT MAY OCCUR. IT MUST
BE UNDERSTOOD THAT COMMON SENSE
AND CAUTION ARE FACTORS WHICH MUST
BE APPLIED BY THE OPERATOR
1. DO NOT use tester if damaged.
2. Maintain the tester in good and clean
condition for best and safest performance.
3. If required, ensure vehicle to be worked on is
adequately supported with axle stands, ramps
and chocks.
4. Wear approved eye protection. A full range of
personal safety equipment is available from
your CLARKE dealer.
5. Wear suitable clothing to avoid snagging. Do
not wear jewellery and tie back long hair.
6. Account for all tools and equipment being
used and do not leave them in, on or near the
engine.
7. When not in use, place in protective case and
store in a safe, dry, childproof area.
PREPARATION.
1. Run the engine until normal operating
temperature is reached.
2. Stop engine and disconnect all spark plug
wires, numbering them according to the
cylinder to which they were connected.
3. Loosen spark plugs one turn but do not
remove them
• This will dislodge any dirt that has
accumulated in the spark plug wells.
4. Use an air hose to blow dirt and debris from the
spark plug wells.
5. Remove the spark plugs and place them on a
clean, flat surface in the cylinder order in
which they were removed.
6. Remove the air filter and set the throttle to the
wide open position, taking care not to
damage the linkage or throttle components.
WARNING: THE IGNITION SYSTEM MUST BE
DISABLED. FAILURE TO DISABLE COULD
RESULT IN DAMAGE TO THE IGNITION SYSTEM
OR ECU.
7. Disconnect the ignition system, following the
manufacturer’s recommendations in the
vehicle servicing manual.
• It is also good practice to unplug the fuel
injectors or disable the fuel pump, especially
on cars fitted with a catalytic convertor. This
prevents unburned fuel getting into the
exhaust system during the test.
IMPORTANT: Always refer to the vehicle
manufacturers service instructions or a
proprietary manual, to establish the current
procedure and data. These instructions are
provided as a guide only.
Parts & Service: 020 8988 7400 / E-mail: [email protected] or [email protected]
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COMPRESSION TEST
GAUGE READINGS
1. Using the appropriate threaded adaptor,
screw the tester into a spark plug hole as
shown (finger-tight - do not use a wrench) or
using the push fitting, hold the compression
tester firmly against the spark plug aperture.
2. Crank the engine until no increase in pressure
is noted on the gauge reading; usually 3 or 4
revolutions is sufficient. Take a note of the
pressure reading.
3. Decompress the tester by pressing the release
valve as shown below.
1. On a normal cylinder, the gauge needle
should travel up the scale on each
compression stroke until it reaches peak value.
All cylinders should indicate a pressure that is
within the vehicle manufacturer’s
specifications, and the reading should not vary
by more than 10% from cylinder to cylinder.
2. If the gauge needle does not travel up the
scale or if it remains at the same value for
several strokes and then starts to climb, the
problem could be a valve sticking.
3. If the compression reading is considerably
higher than the vehicle manufacturer’s
specification, the problem may be carbon
build-up in the cylinder. It may also indicate
that either the piston, or the cylinder head, has
been modified.
4. If a reading on two adjacent cylinders is 20psi
(or more) lower than the other cylinders, the
problem may be a cracked cylinder head or
defective head gasket. Under these
conditions, both coolant and oil may be found
in both cylinders.
5. If the readings are low, or vary widely between
cylinders, pour a teaspoon of SAE 30 oil into each
cylinder and retest them. If the readings increase
considerably, the problem may be poorly seated, or
worn piston rings. If the readings remain about the
same, the valves and/or associated components
may be the problem. A burned or damaged piston
may also cause the same results.
4. Remove the compression tester from the spark
plug hole and proceed to the next cylinder.
• Take a note of the pressure reading for
each cylinder.
AFTER TESTING
1. Clean, re-gap and reinstall the spark plugs in
the same order in which they were removed,
or install new spark plugs.
2. Reconnect each spark plug lead to the plug it
was connected to prior to removal.
3. Return the throttle to the closed position.
IMPORTANT: After test, failure to return the
throttle plates to the closed position before
starting the engine can cause serious damage
to the engine.
4. Reconnect the ignition system.
Parts & Service: 020 8988 7400 / E-mail: [email protected] or [email protected]
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