Piper Navajo PA-31 Service Manual page 562

PIPER NAVAJO SERVICE MANUAL
8B-25. SPARK PLUGS. (Refer to Spark Plugs, Section VIII and Figure 8B-23.)
8B-26. STARTING VIBRATOR.
8B-27. STARTING VIBRATOR CHECKING PROCEDURE.
a. Disconnect all spark plug leads from the left magneto at the spark plugs.
WARNING
Be sure all magneto spark plug leads are removed, thus
preventing the hazardous condition of plug firing during test.
b. Rotate engine crankshaft until number one cylinder is in its retard firing position.
Using the timing light, check to see that the retard contact assembly and both magneto main
contact assemblies are open.
c. Electrically disconnect starter solenoid or remove battery cable from starter so that
the engine will NOT crank during this test.
WARNING
It is necessary that the starter be electrically removed from
the circuit before the vibrator is put into operation to
eliminate possibility of starter being energized during the
test.
d. Place the magneto switch in its "ON" position and actuate the starter switch. At the
same time, observe the No. 1 cylinder spark plug lead which is fired by the left magneto
circuit. A series of sparks should be seen when holding the lead approximately .19 of an
inch from engine ground.
WARNING
Grasp the spark plug lead far enough away from the
connection so as not to produce any dangerous electrical
shock.
e. If the spark does not jump the gap, check the applied voltage to the starting
vibrator. This voltage should be 24 volts.
f. If voltage is correct, check the contact points of the magneto. Both sets of contact
points shall be opened.
g. Reject all units not complying with the preceding requirements or which show any
visual defects.
Reissued: 10/12/79
POWER PLANT
2L16