Lycoming TEO-540-C1A Maintenance Manual page 238

(d) Pull the EECS power circuit breaker.
(e) Make sure that the aircraft master switch and fuel supply switches are all in the OFF
position.
(f) After the engine is shut down, complete the Cylinder Compression Check
immediately to get an accurate measurement.
(g) Set the aircraft brakes and install the wheel chocks.
CAUTION
(2) Disconnect the battery.
CAUTION
(3) Disconnect all of the spark plugs leads per the "Spark Plug Removal" procedure in
Chapter 74-20.
(4) Remove a spark plug from each cylinder. Discard the spark plug gasket.
CAUTION
(5) Turn the crankshaft by hand in the direction of propeller rotation to put the piston in a
position as close to Top Dead Center (TDC) on the compression stroke as possible.
(6) Install the threaded end of an adapter with a coupling end in the spark plug hole of the
cylinder to be tested.
(7) Make sure that the air valve on the differential compression tester is in the CLOSED
position.
(8) Connect the differential compression tester to the adapter and to a clean source of
compressed air.
CAUTION
NOTICE: Operate the differential compression tester per the manufacturer's instructions.
(9) Adjust the regulator of the compression tester to 0 psi (0 kPa) on the regulated pressure
gage.
(10) Connect the differential compression tester to the adapter in the spark plug hole of the
cylinder to be tested.
(11) One mechanic holds the propeller firmly in place, to prevent crankshaft rotation, while
the other mechanic opens the cylinder pressure valve in the next step.
72-30
Page 208
TAKE ALL NECESSARY PRECAUTIONS AGAINST
ACCIDENTAL ROTATION OF THE CRANKSHAFT/PROPELLER
TO PREVENT INJURY.
IGNTION LEADS AND SPARK PLUGS ARE VERY HOT. IN THE
NEXT STEP, WEAR PERSONAL PROTECTIVE GEAR TO PREVENT
BURNS.
USE GLOVES OR RAGS TO PROTECT HANDS WHILE HOLDING
THE PROPELLER BLADE.
BEFORE CONNECTION OF THE COMPRESSION TESTER, MAKE
SURE THAT THE AIR SUPPLY REGULATOR DOES NOT SHOW
MORE THAN 80 PSI (552 KPA) OF AIR PRESSURE. EXCESSIVE
AIR PRESSURE CAN CAUSE THE PROPELLER TO TURN. KEEP
CLEAR OF THE ROTATIONAL RADIUS OF THE PROPELLER.
TEO-540-C1A Engine Maintenance Manual
TEO-540-C1A Engine Maintenance Manual
© 2018 Avco Corporation. All Rights Reserved
November 2018