Piper COMANCHE PA-24-180 Service Manual page 580

PIPER COMANCHE SERVICE MANUAL
9-62. Cranking Motors. (Delco-Remy)
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9-63. General. When the cranking motor switch is closed, the armature begins to rotate The drie pinion.
being a loose fit on the drive sleeve located on the armature shaft. does not pick up speed as fast as the
armature Therefore. the drive pinion. having internally matched splines with respect to the splines drne
sleeve. moves endwise on the shaft and into mesh with the flwheel 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 11! wheel
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 pre ents the pinion from drifting into mesh when the engine is running. Others use a smallanti-drift pin
and spring inside the pinion which provides enough friction to keep the pinion from drifting into mesh
Nexer operate the motor for more than 30 seconds without pausing for two minutes 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 batterV
b Inspect the viring 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 an! other
control switch. and battery. including all ground connections Clean and tighten all connections and wmring
as required Man! engine manufacturers specify allowable voltage drops in the cranking circuit For this
information. refer to the engine manufacturer's shop manual
c Inspect all control switches and the ignition switch. to determine their condition. Connect a jumper
lead around any switch suspected of being defective If the system functions properl! using this method, repair
or replace the bypassed switch
d. If specified batter! voltage can be measured at the motor terminal of the cranking motor. allowing
for some voltage drop in the circuit and the engine is known to be functioning properly. remove the motor and
follow the test procedures
9-65 Test And Maintenance Of Cranking Motor. (Delco-Remy)
9-66 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 b\ turning the pinion Tight. dirty. or worn bearings. bent armature shaft. or loose pole shoe screw
will cause the armature to drag and it w ill not turn freely If the armature does not turn freel the motor should
be disassembled immediately. However. if the armature does operate freely. the motor should be given
electrical tests before disassembly (Refer to Paragraph 9-73 )
9-67 Checks.
ISSUED: 8/18/72
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ELECTRICAL SYSTEM