Newly installed engines shall be
given a depreservation run as soon
as possible, but not later than 4
accomplished if more than 4 hours
has elapsed since preoiling engine,
complete preoiling procedure shall
again be accomplished.
(1) Prior to starting engine, remove one spark plug
from each cylinder below the horizontal centerline of
engine. Refer to TB 55-2925-200-25 for proper spark
plugs to be utilized during depreservation run.
On seven-cylinder engines which
would necessitate removal of spark
plugs from four cylinders, thereby
operation, the one cylinder below the
horizontal centerline on right side of
engine when viewing engine at
propeller end may be left operative.
cylinders rather than three, which
greatly stabilizes engine operation.
(2) Install approved depreservation valve in each
open plug hole.
Install length of hose on each
depreservation valve to vent large
quantities of oil overboard. This
accumulation of oil around cylinder
(3) All spark plug leads, except those removed to
permit Installation of depreservation valves, will remain
connected to spark plugs. Install metal shipping caps to
The metal shipping caps ground out
excessive voltage buildup in the
magneto and possibility of flash-over
at terminal end of ignition lead.
(4) Start engine and run at 800 to 1500 rpm for 30
seconds to 1 minute. Operation may be accomplished
on either primer or carburetor, or both, to obtain
smoothest possible operation.
operation is obtained at higher
engine speeds and a higher air
velocity through Intake pipes will
result In cases where extreme
cold temperatures exist, engine
preheated prior to starting and
should be allowed to run longer
provided excessive vibration Is
if present in Intake pipes, will
have adequate time to be heated
through external drain or into
expelled into exhaust system or
through depreservation valve.
(5) Stop engine by closing throttle and discontinuing
use of primer or by moving mixture control to IDLE
(6) Install spark plugs, Ignition leads, engine
cowling, etc., and proceed to start engine using
prescribed starting procedures outlined in the applicable
Spark plugs used for depreservation
runs shall be replaced with new or
placing the engine in service.