Piper Navajo PA-31 Service Manual page 500

PIPER NAVAJO SERVICE MANUAL
f. After both magnetos have been timed, leave the timing lightwires connected
and recheck magnetos as previously described to make sure that both magnetos
are set to fire together.
If timing is correct, both timing lights will go out simul-
taneouslywhen the timing marks are inalignment. Tighten nuts to specified torque.
g. After magnetos have been properlytimed,
replace breaker cover and secure.
h. Install the ground lead and the retard spark lead on the left magneto.
i . Place the harness terminal plate on the magneto and tighten nut around the
plate alternately to seat cover squarely on magneto. Torque nuts to 18 to 22 inch
pounds.
8-57. HARNESS ASSEMBLY.
8-58. INSPECTION OF HARNESS.
a.
Check lead assemblies for nicks, cuts, mutilatedbraiding, badly worn sec-
tion or any other evidence of physical damage. Inspect spark plug sleeves for
chafing or tears and damaged or stripped threads on coupling nuts. Check com-
pression spring to see if it is broken or distorted. Inspect grommet for tears.
Check all mounting brackets and clamps to see that they are secure and not cracked.
b. Using an ohmmeter, buzzer, or other suitable low voltage device, check
each lead for continuity. If continuity does not exist, wire is broken and must be
replaced.
c. For electrical test of harness assembly, use a high voltage, direct current
tester such as the TAKK Model 86 or 86A or an equivalent direct current high
voltage tester capable of delivering a test potential of 10,000 volts.
Connect
ground lead of high voltage tester to outer shielding braid of a single lead. Con-
nect plug terminal. Turn tester "ON" and apply 10,000 volts. The insulation
resistance
should be 100 megohms minimum. Proceed to check other leads of
harness in same manner.
d. Minor repair of the harness assembly, such as replacement of contact
springs, spring retainer assemblies, insulating sleeves or of one lead assembly,
can be accomplished with the harness assembly mounted on the engine. However,
should repair require replacement of more than one lead assembly or of a cable
outlet plate, the harness should be removed from the engine and sent to an over-
haul shop.
8-59. REMOVAL OF HARNESS.
a. Disconnect the clamps that secure the wires to the engine and accessories.
b. Loosen the coupling nuts at the spark plugs and remove the insulators from
the spark plug barrel well. Use caution when withdrawing the insulator
not to
damage the insulator spring.
Reissued: 10/12/79 POWER PLANT
2J2