Cranking Motor Check; Cranking Motor Test And Maintenance - Piper PA-24 Comanche Service Manual

PIPER COMANCHE SERVICE MANUAL
9-61. Cranking Motors. (Delco-Rem)')
•
9-63. General. When the cranking motor switch is closed. the armature begins to rotate. The
drive
pinion.
being a loose fit on the drive sleeve located on the armature shaft. does not pick up speed as fast a" the
armature. Therefore. the drive pinion. having internally matched splines with respect to the splines
drive
sleeve. moves endwise on the shaft and into mesh with the flywheel, As the pinion hits the pinion stop. it begins
to rotate with the armature and cranks the engine.
When the engine starts. the flywheel begins to spin the pinion faster than the armature. Again. because
of the splined action of the pinion and drive sleeve assembly. the pinion backs out of mesh with the
ll~
\\ heel
ring gear protecting the armature from excessive speeds.
Some Bendix drives incorporate a small anti-drift spring between the drive pinion and the pinion stop
which prevents the pinion from drifting into mesh when the engine is running. Others use a small anti-drift pin
and spring inside the pinion \\ hich provides enough friction to keep the pinion from drifting into mesh.
:\ever operate the motor for more than 30 seconds without pausing for two mi nutes to allow it
to
cool.
9-64. Checking Cranking Motor. Several checks. both visual and electrical. should be made in a defective
cranking circuit to isolate trouble before removing any unit. Many times a component is removed from the
aircraft only to find it is not defective after reliable tests. Therefore. before removing a unit in a
defective
cranking system. the following checks should be made:
a. Determine the condition of the battery,
b. Inspect the wiring for frayed insulation or other damage. Replace any wiring that is damaged.
Inspect all connections to the cranking motor. solenoid or magnetic switch. ignition switch or any other
control switch. and battery. including all ground connections. Clean and tighten all connections and wiring
as required. Many engine manufacturers specify allowable voltage drops in the cranking circuit. For t .
information. refer to the engine manufacturer's shop manual.
c. Inspect all control switches and the ignition switch. to determine their condition. Connect a jumpei
lead around any switch suspected of being defective.Hthe system functions properly using this method. repair
or replace the bypassed switch.
d. If specified battery voltage can be measured at the motor terminal of the cranking motor. allow ing
for some voltage drop in the circuit and the engine is known to be functioning properly. remove the motor and
follow the test procedures.
9·M. Test And Maintenance Of Cranking Motor. (Delco-Remy)
9-M.
Inspection. With the cranking motor removed from the engine. the pinion should be checked for
freedom of operation by turning it on the screw shaft. The armature should be checked for freedom of
operation by turning the pinion. Tight. dirty. or worn bearings. bent armature shaft. or loose pole shoe screw
will cause the armature to drag and it will not turn freely.
If
the armature does not turn freely the motor should
be disassembled
irnrnediatelv.
However. if the armature does operate freely. the motor should be given
electrical tests before disassembly. (Refer to Paragraph 9-73.)
9-67. Checks.
ISSl"ED: 8/18/72
3CIO
ELECTRIC AL SYSTE'