MCi Crusader II 1989 Maintenance Manual page 236

Date 1-1-89
Page
7-16
MC-9 MAINTENANCE MANUAL
SEAMLESS, ONE-PIECE SOLENOID CASE
LOW FRICTION BUSHING .
0
.. RING
Oil WICK
REMOVABLE
END CAP FOR
INSPECTION
GASKET
SHAFT SEAL
SEALING BOOT
BRONZE BEARING
TOTALLY ENCLOSED
SHIFT MECHANISM
-PIECE HOUSING
Figure 7-35. 42-MT Starting Motor Cross Section (after Dec. 1985).
The pinion is moved into mesh with the ring gear by the
action of the solenoid. The pinion remains engaged uni,1 the
solenoid circuit is interrupted. In case of a butt engagemeri! the
motor will not be energized to prevent damage to the pinion and
gear teeth.
· Under normal operating conditions. no maintenance will be
required between engine overhaul periods. At time of engine
overhaul, motors should be disassembled, inspected. cleaned
and tested as described in succeeding paragraphs.
A basic circuit is shown in figure 7-36. When the start switch
is closed, the magnetic switch contacts close. and the solenoid
windings are connected to the battery. The resulting plunger ·
and shift lever movement causes the pinion to engage the
engine flywheel ring gear and the solenoid main contacts to
close, and cranking takes place.
When the engine starts. pinion overrun protects the arma-
ture from excessive speed until the switch is opened, at which
time the return spring causes the pinion to disengage. To pre-
vent excessive overrun and damage to the drive and armature
windings, the switch must be opened immediately when the
CONHtCT 10 GlOUN0
IMAT I! DllfCT GIOUND
A$ SHOWN 01 U410UGH
,1,01.0 UL,1,T_ OIL 1'11!55,UH
$WITCH. ,utL l'lfUUlt
$WITCH 01 OTHU
CONTIOl UNl11
Figure 7-36. Basic Starting Circuit.
engine starts. A cranking period for all types of motors should
never e'5ceed 30 seconds without stopping to allow the motor
to cool.
Either of two types of starter protection may be present on
the MCI Series of coaches. Later production (1987) coaches
have the 3N124 Triple Protection Device as standard
equipment The optional Thermal Time Delay Relay may have
been installed in lieu of the basic device. Earlier coaches may
also have either of these devices, which would have been
installed as optional or special equipment
One of the functions of the Tripple Function Protective
Device is to prevent starter re-engagement after the engine is
running. Further information on this device can be found later
in this section.
The optional Thermal Time Delay Relay prevents starter
overheating by lim1t1ng the time the starter can be cranked
without pause. It differs from the standard protection device in
that it does not sense overvottage to protect electrical compo-
nents. nor ·does it prevent starter re-engagement when the
engine 1s running.
The Thermal Time Delay Relay provides a 20-second timed
start period followed by a 20-27-second reset delay to allow the
starter to cool. Refer to the Thermal Time Delay wiring diagram
later 1n this section.
TROUBLESHOOTING THE CRANKING CIRCUIT
If the cranking system is not periorming properly, make the
following checks to help determine which part of the circuit isat
fault. Insure that the battery is fully charged. The wiring,
switches and starting motor cannot be checked if the battery is
defective or discharged.
1. Inspect the wiring for damage. Inspect all connections to
the starting motor. solenoid. magnetic switch. ignition _switch or