Piper PA-24 Comanche Service Manual page 427

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PIPER COMANCHE SERVICE MANUAL
7S-S0. ImpecUoD AJld Claniq Of Sparkftu,.
a. Visually inspea each spark plu,
fOf
the foUowinl
non~ep&inble
defeca:
1. Severely
damaJcd
sheUor shield mreads nicked Ill'. stripped or aoatbreaded.
Z. Badly battered or rounded $beU hexqons.
3.
Out-of-round or
damated sJUeldinc barrel.
4. Chipped. cnc:ked. or brokcli ceramic iNulator portions.
S. Sadly eroded electrodes 'Nom to approximately 5Q4K, of oriJinal size.
b. Clea.n the spark plu,
as
requited.
ranoYint carbon
and for. deposia.
c. Test the spuk plUl both eleetric:a11y and for resistance.
d. Set the electrode ,ap at .015 to .018 of
all
inch or if a smoother operation at idle speed and
reduced mllftCto drop-off is desired. set at .018 to .022 of
an
inch.
However.
with wjde
,ap
seain, the
plup must be serviced at man: frequent inmvals. Fine wile platiDum or iridium electrodes should be
set
at
.015 to .018 of an inch only.
78-51. InltlJJation Of Spark Plup. Before
installint
spuk I'
lUIs. uccmin mat the threads within the
cylinder are clean and not ciarnqed.
a. Apply anti-sei:ze compound
spatinllY
on the threads and
install ,askee
and spark pl\lls. Torque 360
to ~20 inc:h pounds.
CAUTION
.\t~e
ccttain the decp socket is properly seated on the
spuk
plUl
hexqan as
damage
to thc plu, could result
if the wrench is cocked to
one side when pressure is applied.
b. Carefully insert the terminal insulator in the spark plu, and tilhten the cOl&pling nut.
78·' Z. Lubrication Synem.
78-33. Oil Relief Valve. Thc function of the oil pressure relief valve. which is located between the upper
rilht engine mounttn,lul and NO.7 cylinder. is to maintain'eftline oil pressure withill specified limitS by
withdn.win, a portion of the oil from the circul.atinl system and retw'1'lin, the oil to the sump should the
prcnure become excessive. This valve is not adjustable. however. particles of metal or other foreJgn matter
lodled between ball and seat will result in a drop in oil pressure. It
is advisable. therefore. to disassemble.
inspect U1d clean the relief valve if excessive pressure fluctuations are noted.
The oil pressure relief valve is by no means to be confused with the oil
eocter
by-pus valve. which
IS
located on the ou pressure screen housina mountiftt pad. The sole purpose of the by-pass valve is to serve as
.1
safety meuure. permittin!J pressure oil to byoplSS the oil cooler entirely in case of an ebserucncn wuhin
the cooler,
POWER PLANT
ISSUED: 8/18/72
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