Piper Navajo PA-31 Service Manual page 554

PIPER NAVAJO SERVICE MANUAL
o. Reinstall the plugs in the timing inspection holes and torque to 12-15 inch-pounds.
Loosely install the harness with clamps and/or brackets.
8B-21. MAGNETO TIMING PROCEDURE. (Internal Timing.) The use of the timing light
unit, Part No. 11-9110, available from Bendix will simplify the internal timing procedure
and breaker synchronization.
a. Connect the timing light black lead to any unpainted surface of the magneto.
b. Connect the red timing light lead to the left breaker terminal and the green lead to
the right main breaker terminal. (Refer to Figure 8B-10.)
c. Back the engine up a few degrees and then bump it forward toward the number one
cylinder firing position while observing the timing lights.
NOTE
Both lights should go out to indicate opening of the main
breakers when the timing pointer is indicating within the
width of the "L" or "R" mark.
d. If breaker timing is not correct, loosen the breaker screws and correct the setting.
Retorque the breaker screws to 20-25 inch-pounds.
NOTE
With the magneto rotor positioned according to step c, the
engine may not be exactly in number one cylinder firing
position as indicated by the engine timing mark depending on
extent of play in gear train.
e. Remove the timing light lead from the main breaker terminal. Attach the red lead to
the retard breaker terminal.
f. Bump the engine forward as described in step c, until the pointer is aligned with the
applicable retard timing mark of 15°. The retard breaker should just open at this position.
g. If retard timing is not correct, loosen the screw securing the cam and turn the retard
breaker cam as required to make the retard breaker open per step f. Torque the non-self lock-
ing cam screw from 16-20 inch-pounds. Refer to the latest revision of Lycoming Service
Instruction No. 1400 for information regarding replacement of cam retaining screw.
NOTE
If correct breaker timing cannot
be achieved, remove
magneto and have it overhauled.
h. Check capacitors for looseness in the magneto cover of the harness assembly and for
any physical damage. The capacitors should be checked for capacitance, series resistance and
leakage. Capacitance should be 0.34 to 0.41 microfarads. The use of a Bendix condenser
tester, Part No. 11-1767-1, -2 or -3 or equivalent will simplify this test. Replace defective
capacitors and torque securing nut to 60-70 inch-pounds.
Revised: 9/2481
2L8
POWER PLANT
2L8