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SeCTIoN 8: eleCTrIC STArTer

INTroduCTIoN

Some GN/GSH series engine applications may be equipped

with a 2 Volt DC electric cranking system. Such a system con-
verts electrical energy from a battery into mechanical energy
at the starter motor, for the purpose of turning the engine
over for starting.

NOTE: Cranking systems discussed in this manual are
typical systems. The actual cranking system used in spe-
cific applications may differ. Refer to the wiring diagram
and/or electrical schematic in the Owner's Manual for
specific applications.

STArTer MoTor oPerATING PrINCIPleS

Closure of the circuit to the starter motor allows battery

current to flow through a commutator, to the loops of wire in
the armature, and back to the battery. The interaction of the
magnetic fields causes the armature to revolve.

The armature rotates at a relatively high speed to provide suf-

ficient torque to crank the engine. The required engine cranking
speed is relatively slow, so the starter motor is equipped with
a small drive pinion that meshes with the teeth of a flywheel
ring gear to crank the engine. The large ring gear and the small
starter pinion gear results in a gear reduction that can vary in
ratio up to 9-to-. This reduction allows the starter to rotate
at high speeds while cranking the engine at low speeds.

When the engine starts, its speed increases quickly. For

example, if the engine reaches 00 rpm and the starter pinion
remains meshed with the ring gear, the starter armature would
spin at about ,900 rpm (9-to- ratio). To prevent damage
to the armature, a "Bendix Drive" mechanism is used to dis-
engage the starter pinion from the ring gear when the engine
has started.

THe beNdIX drIve

When the field coils of the starter drive are energized, the

armature starts to turn. A loose fitting sleeve inside the pinion
gear is turned with the armature. This sleeve has large spiral
threads on its surface that match the pinion gear’s internal
threads. The sleeve turns with the armature, and the pinion
gear rotates on the threads to move outward on the sleeve.
Outward movement of the pinion gear causes that gear to
mesh with the flywheel ring gear. The pinion hits a stop on
the sleeve, and the pinion turns the ring gear and engine. On
start-up, the engine turns faster than the armature. This causes
the pinion to spin back on the spiral threads of the sleeve and
out of engagement with the ring gear.

STArTer MoTor rePAIrS

If the starter motor is defective, it should be removed and

replaced. Disassembly and repair of the motor is not cost
effective.

STARTER MOTOR REMOVAL:

Note: Before removing starter, disconnect the negative
battery cable from the battery.

To remove the starter from the engine, loosen and disconnect

the starter wire, then remove the two hex head screws that
hold the starter in place.

STARTER MOTOR INSTALLATION:

To install the starter motor, reverse the previous steps.

TeSTING THe STArTer MoTor

CHECKING THE PINION:

When the starter motor is activated, the pinion gear should

rise and engage the ring gear. If the pinion does not rise nor-
mally, inspect the large spiral threads of the sleeve and pinion
for binding or sticking.

TOOLS FOR STARTER PERFORMANCE TEST:

The following equipment may be used to complete a per-

formance test of the starter motor:

•  A digital multimeter (VOM).
•  A tachometer capable of reading up to ,500 rpm.
•  A fully charged 2 Volt battery.

STARTER PERFORMANCE TEST:

. Set the meter to read DC amps.

2. Connect the starter motor, battery and VOM as shown in

Figure 8-2.

VOM

VICE

TACHOMETER

STARTER