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TM 10-4320-324-14
1-21. Electrical System.
a.
Batteries. Two 12 volt, 100 ampere hour, lead acid batteries. Supply power to all pumping assembly electrical circuits.
b.
Emergency Stop Switch (S1). Two position PUSH-PULL switch. PULL position provides normal operation. PUSH
position cuts off power and shuts down assembly. Provides rapid engine shut down in event of emergency.
c.
K2 Relay. A normally open relay, actuated by the By-Pass switch during start. Held closed when oil pressure reaches 4
to 7 psi and K1 relay is closed. K2 provides power to actuate fuel shutdown solenoid.
d.
Fuel Shutdown Solenoid. A two position 12 VDC rack type solenoid. Attached to governor cut-off lever, it provides
positive fuel cut-off to shutdown engine. When fully retracted (fuel open), auxiliary tap (A) actuates K1 relay.
e.
K1 Relay. A normally open relay, actuated by auxiliary tap (A) of fuel shutdown solenoid. One contact of relay when
closed, provides path for current flow from start switch to starter solenoid. Second contact of relay provides current flow
through V-belt contact switch and low oil pressure switch to K2 relay coil.
f.
Oil Pressure By-Pass Switch (S3). A spring loaded off push button switch. Used only during engine start. When
depressed, switch by passes low oil pressure switch. K2 relay then energizes to allow fuel shutdown solenoid to retract
(fuel open) and K1 relay coil to energize.
g.
Start Switch (S2). Spring loaded. When depressed (simultaneously with oil pressure bypass switch), directs current
through K1 relay contact to starter solenoid coil K3.
h.
Starter Solenoid. A normally open 12 VDC coil. When energized, engages starter drive with engine flywheel and allows
battery power to rotate starter motor. Solenoid deenergized when start button released. Starter then disengages from
engine.
i.
V-Belt Contact Switch (S4). A normally closed switch. Provides current path in series with low oil pressure switch and
K1 relay contact keeping K2 relay coil energized. If cooling blower V-belts breaks, switch will open deenergizing K2 relay
coil. When K2 opens, fuel shutdown solenoid extends (fuel closed) and engine shuts down.
j.
Low Oil Pressure Switch. A normally open switch. Closes when oil pressure reaches 4 to 7 psi while starting. As long as
oil pressure remains above close point, switch provides current path in series with V-belt contact switch and K1 relay
contact keeping K2 relay coil energized. If oil pressure drops below 4-7 psi, pressure switch opens deenergizing K2 relay
coil. When K2 opens, fuel shutdown solenoid extends (fuel closed) and engine shuts down.
1-15
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