Piper COMANCHE PA-24-180 Service Manual page 327

NOTE
Spark plugs should not be used if they have been dropped.
d.
Removal of seized spark plugs in the cylinder may be accomplished by application of liquid carbon
dioxide by a conical metal funnel adapter with a hole at the apex just large enough to accomodate the funnel
of a C02 bottle. (Refer to Figure 7-17.) When a seized spark plug cannot be removed by normal means. the
funnel adapter is placed over and around the spark plug. Place the funnel of the C02 bottle inside the funnel
adapter and release the carbon dioxide to chill and contract the spark plug. Break the spark plug loose with
a wrench. A warm cylinder head at the time the carbon dioxide is applied will aid in the removal of an
excessively seized plug.
e.
Do not allow foreign objects to enter the spark plug hole.
7-51. Inspection And Cleaning Of Spark Plug.
a.
Visually inspect each spark plug for the following non-repairable defects:
1.
Severely damaged shell or shield threads nicked up, stripped or cross-threaded.
2.
Badly battered or rounded shell hexagons.
3.
Out-of-around or damaged shielding barrel.
4.
Chipped, cracked, or broken ceramic insulator portions.
5.
Badly eroded electrodes worn to approximately 50% of original size.
b.
Clean the spark plug as required. removing carbon and foreign deposits.
c.
Test the spark plug both electrically and for resistance.
d.
Set the electrode gap at .015 to .018 of an inch or if a smoother operation at idle speed and reduced
magneto drop-off is desired. set at .018 to .022 of an inch. However, with wide gap setting the plugs must be
serviced at more frequent intervals. Fine wire platinum
or iridium electrodes should be set at
.015 to .018 of an inch only.
ISSUED: 8/18/72
POWER PLANT
2B17
PIPER COMANCHE SERVICE MANUAL
FIGURE 7-17. REMOVING SEIZED SPARK PLUG