Piper Comanche PA-24 Service Manual page 710

PIPER COMANCHE SERVICE MANUAL
9-62, Cranking Motors. (Delco-Remy)
9-63, General. When the cranking mOlOr switch is closed. the armature begins to rotate The dri\'e 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. ha,ing internally matched splines with respect to the splines dri,e
sleeve. moves endwise on the shaft and into mesh with the nywheel As the pinion hits the pinion stop. it begins
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rotate with the armature and cranks the engine,
When the engine starts. the nywheel begins
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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
n~
wheel
ring gear protecting the armature from excessi,'e speeds,
Some Bendix drives incorporate a small anti-drift spring between the drive pinion and the pinion ,top
which pr"ents the pinion from drifting into mesh when the engine is running. Others use a small anti-drift pin
and spring inside the pinion which pro"ides enough friction
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keep the pinion from drifting inlO mesh
'"er operate the motor for more than 30 seconds without pausing for two minutes to allow it to cool
9-64 Checking '::ranking Motor. Se"ral checks. both ,isual and electrical. should be made in a defecti\e
cranking circuit
10
isolate trouble before removing any unit Many times a component IS remO\ed from the
aircraft only
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find it is not defecti" after reliable tests, Therefore. before remO\'ing a Unit in a defecti\e
cranking system. the following checks should be made
a Determine the condition of the bal\ery
b Inspect the wiring for frayed insulation or other damage Replace any wiring that is damaged
Inspect all connections
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the cranking mOlOr. solenoid or magnetic switch. ignition switch or am other
control switch. and bal\ery. including all ground connections Clean and tighten all connection- and wIfing
as re4uired
Man~
engine manufacturers
specif~
allowable, oltage drops in the cranking circuit For thi_'
information. refer to the engine manufacturers shop manual
c I nspect all control sw itches and the ignition switch. to determine their cond ition, Connect ajumpe
lead a round any switch suspected of being defective If t he system functions
propcrl~
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. allowing
for some voltage drop in the circuit and the engine is known to be functioning properly. remo'e the motor and
follow the test procedures
9-/>5 Test And Maintenance
or
Cranking Motor. (Delco-Remy)
9-/>1> Inspection. With the cranking mOlOr 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. diny, 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 armalUre does not turn
freel~
the motorshould
be disassembled immediately, How,,'er. if the armature does operate freel,'. the motor should be gi\en
electrical tests before disassembly (Refer to Paragraph 9-73 )
9-67 Checks.
3CIO
ELECTRICAL SYSTE_