Operator`s manual

Section 9
Test Procedure
OVERHAUL
MANUAL
LYCOMING DIRECT DRIVE AIRCRAFT ENGINES
9-23.
Non-adjustable
Oil
Pressure Relief
Valve
- Al-
though
the valve is not
adjustable, the oil pressure
can be controlled
by
the addition
of STD-425
washers
under
the cap
as required
(maximum
of three)
to in-
crease pressure
or the
use of a spacer
(P/N
73629 or
73630)
to decrease
pressure.
A later modification
to
the
relief valve
eliminates
the need
of the spacer
and
uses STD-425
washers
as required
(maximum
of nine).
Particles of metal or
other foreign matter between
the
ball and
the seat
can cause the
oil pressure
to drop
or
fluctuate.
Therefore,
if
a drop or excessive
fluctuation
is noted it is advisable
to disassemble,
inspect and
clean the valve.
9-24.
Adjustable
Oil ReliefValve
- The
adjustable
oil
pressure relief valve
enables the operator
to main-
tain engine
oil pressure within the
specified limits (see
Table 9-1).
The oil
pressure can
be adjusted
by turn-
ing
the adjusting
screw
in toincrease
pressure
or out
to decrease
pressure.
The adjusting
screw
can be
turned
with either
a screw
driver or
a socket wrench.
9-25. IDLE
SPEED
AND MIXTURE
ADJUSTMENT
-
(Except Simmonds
Fuel
Injector).
See figures
9-1 and
9-2. With engine
thoroughlywarmedup,
check
magneto
drop-off. If
the drop-off is excessive,
check for fouled
plugs. If drop-off
is normal, proceed
with idle ad-
justment.
Close
the throttle,
engine
should idle
at ap-
proximately
600 RPM
(turbocharged
engines,
approxi-
mately
1000 RPM). If the RPM
increases appreciably
after
a change in the idle
mixture adjustment
during
the succeeding
steps, readjust the idle
speed adjust-
ment to restore
the desired
RPM.
Figure 9-2. Carburetor - HA-6
d(2). Turn combination magneto-starter switch to
"start".
e(1). When engine
fires, move mixture
control
smoothly
to "Full Rich" on pressure
carburetor
or
Bendix fuel injectors.
e(2). Leave float type carburetors and Simmonds
injectors in "full rich".
f(1). Move magneto
switch to
"both".
f(2).
Combination spring
loaded switches will
return
to "both".
CAUTION
If oil pressure
is not indicated
within ten
seconds, stop engine
and determine
cause.
9-19.
Operate engine at
approximately 1000 RPM
un-
tila minimum oilin
temperature of 140
°
F. is obtained.
Check magneto
drop-off and general
operation of the
engine. Check the engine for oil leaks. Any malfunc-
tion
or oil leak should be
remedied before continuing
the run.
9-20. Complete
the run in accordance
with the sched-
ule listed in Table 9-2.
9-21.
OIL CONSUMPTION
RUN. An oil consumption
run should be made
at the end of the run-in
schedule.
Oil consumption can
be determined by the
use of a
scale tankthroughwhichthe
oillines pass and
the scale
reading taken at the
beginning and end of the
oil con-
sumption
run. Or
it can be determined
by
draining
and
weighing the oil
supply before and after
the oil con-
sumption
run. Oil temperature
should be held
as closely
as possible to the limits shown in Table 9-1. Oil con-
sumption should
not exceed the maximum
as listed in
Table 9-1.
9-22. OIL PRESSURE
RELIEF VALVE.
Subject en-
gines may be equipped
with either an
adjustable or a
non-adjustable
relief valve.
A brief description,
of
both types,
follows.
9-26. Move
the mixture
control
lever with
a smooth,
steady
pull into
the idle- cut-
off position
and observe
the
tachometer
for
any change
during the
leaning process.
Caution
must be exercised to
return the mixture con-
trol lever to "full rich"
before the RPM can
drop to a
point
where the engine
cuts
out. An increase
of more
than 50 RPM while
"leaning out" indicates
an exces-
sively rich mixture.
An immediate decrease
in RPM
(if not preceded
by a momentary
increase) indicates
the mixture is too lean.
9-27.
If it is indicated that
the mixture is either
too
lean or too rich,
turn the idle mixture
adjustment one
or two notches
in the direction
required for correction.
Check
this setting by repeating
the above procedure.
Each time the adjustment
is changed, the engine
should
be run up
to 2000 RPMto
clear the
engine before
pro-
ceeding with
the idle speed check.
The final adjust-
ment of the
idle speed should be
made with throttle
closed.
9-28.
IDLE SPEED
AND
MIXTURE
ADJUSTMENT
-
(Simmonds
Injector). See figure
9-3. Three adjust-
ments
can be
made for proper
engine
idling conditions.
All three
are made
on the throttle
body
assembly.
1. Throttle
Lever Stop Adjustment
- This adjust-
ment changes
idle speed and mixture
simultaneous-
ly. If engine idles
too slowly turn adjustment
screw
clockwise
until satisfactory
idle is obtained.
2.
Idle Air Bleed Adjustment.
If a satisfactory
idle
is not
obtained by the first
adjustment proceed
as
follows.
9-4
Revised January, 1970