Piper COMANCHE PA-24-180 Service Manual page 417

NOTE
The idle mixture must be adiusted with the fuel boost pump "ON
d
\\'hen the idling speed has been stabilized. mo\e the cockpit mixture control with a smooth. stead!
pull toward the "Idle Cut-Off" position and obser\e the tachometer lor an> change during the "leaning"
process Caution must be exercised to return the mixture control to the "Full Rich" position before the R PM
can drop to a point x here the engine cuts out. An increase of more than 50 RPM while"lea nng out" indicate,
an excessiel\ rich idle mixture An immediate decrease in RPM (11 not preceded b! a momentary increase)
indicates the idle mixture is too lean
e
II the abo\e indicates that the idle adjustment is too rich or too lean. turn the idle mixture adjust-
ment in the direction required for correction. and check this ne\ position by repeating the above procedure
Make additional adjustments as necessary. Each time the adjustment is changed. the engine should be run up
to 2000 RPM to clear the engine before proceeding with the RPM check Make final adjustment of the idle
speed adjustment to obtain the desired Idling RPM with closed throttle The above method aims at a setting
that will obtain maximum RPM with minimum manifold pressure In case the setting does not remain stable.
check the idle linkage. an! looseness in this linkage would cause erratic idling In all cases. allowance should
be made lor the eflect ol
eather conditions and field altitude upon idling adjustment.
7B-33 Fuel Air Bleed Nozzles.
7B-34 Removal Of Fuel Air Bleed Nozzles. ( Reter to Figure 7B-7 ) The nozzles must be caretull! removed
as the\ or the c\linders ma\ be damaged
a
I ift the side access panels ot the engine cowling
b
Disconnect the fuel line from the nozzle
c
Carelully remove the no/le. using the correct si7e deep socket
d Clean and inspect the no/zlc
a
giveln in Paragraph 7B-35
7B-35 Cleaning And Inspection Of Fuel Air Bleed Nozzles.
a
Clean the nozzles w ith acetone or Meth>lethxlketone(MEK))nd
blow out all foreign particles with
compressed air in the direction opposite that of fuel flow Do not use wire or other hard obiects to clean
orifices
b
Inspect the nozzle and cylinder threads for nicks, stripping or cross-threadmng and battered or
rounded hexagons
c
Inspect and replace nozzle O-rings found to be cracked. brittle or distorted Reler to Lycoming
Ser\ice Instructions \o
1275 for detailed test procedure ot air bleed nozzles
7B-36 Installation Of Fuel Air Bleed Nozzle.
a
It is important lor the nozzles to be correctly positioned with the air bleed hole facing upward
b
Install the nozzles and tighten to a little less than 60 inch-pounds torque
c
Continue to tighten the nozzles until the letter or number stamped on the hex of the no/ile bod>
points down In this position the air bleed hole will lace upward
ISS ED: 8/18/72
2F11
PO\ER PIANT
2FI1
PIPER COMANCHE SERVICE MANUAL