Piper Navajo PA-31 Service Manual page 493

PIPER NAVAJO SERVICE MANUAL
d. Connect the vent to the nozzle shroud.
e. Install the spring and spring retainer on the nozzle stem.
f. Connect the fuel line to the nozzle and clamp the fuel lines as described in the latest
revision of Lycoming Service Bulletin No. 335.
g. Install the engine cowl. (Refer to paragraph 8-6.)
8-51. IGNITION SYSTEM MAINTENANCE.
8-52. MAGNETO.
CAUTION
Ascertain that the primary circuit of both magnetos is
grounded before working on the engine.
8-53. INSPECTION OF MAGNETO.
a. After the first 25 hour and 50 hour periods, and periodically thereafter, the contact
assemblies should be checked. Examine the points for excessive wear or burning. Points
which have deep pits or excessively burned areas should be discarded. Examine the cam
follower felt for proper lubrication. If necessary, points can be cleaned by using any hard
finished paper. Clean breaker compartment with dry cloth.
b. If engine operating troubles develop which appear to be caused by the ignition
system, it is advisable to check the spark plugs and wiring first before working on the
magnetos.
c. Should the trouble appear definitely associated with the magneto, the most effective
measure is to install a replacement magneto which is known to be in satisfactory condition
and send the suspected unit to the overhaul shop for test and repair.
d. Should this not be possible, a visual inspection may disclose the source of trouble.
Remove the harness outlet plate from the magneto. Inspect for the presence of moisture and
foreign matter on the rubber grommet and high tension outlet side of distributor block.
Check height of block contact springs (0.422 max. from top of block tower to spring). Also
check for broken leads or damaged insulation. If either is present, remove magneto and
replace.
e. Remove the breaker cover and harness securing screws and nuts, and separate cover
from magneto housing. Check contact assemblies to see that cam follower is securely riveted
to its spring. Examine the contact points for excessive wear or burning. Figure 8-10 shows
how the average contact point will look when surfaces are separated for inspection. Desired
contact surfaces have a dull gray, sand-blasted (almost rough) or frosted appearance, over
the area where electrical contact is made. This means that points are worn in and mated to
each other, thereby providing the best possible electrical contact and highest efficiency of
performance.
f.
Minor irregularities or roughness of point surfaces are not harmful. (Refer to Figure
8-10 center.) Neither are small pits or mounds, if not too pronounced. If there is a
possibility of pit becoming deep enough to penetrate pad, Figure 8-10, right, reject contact
assembly.
POWER PLANT
Revised: 9/24/81
2119