TM 5-3805-281-24-1
Sub-System Diagnostics
STARTING AND FUEL SHUTOFF CIRCUIT
OPERATIONAL INFORMATION
The following conditions must be met for the circuit to
function:
Key switch in START and voltage present at the following:
Starter relay K13 terminal B
Fuel shutoff relay K15 terminal B
Starter M1 terminal C
Fuel shutoff solenoid Y7 hold-in coil terminal
9015
15
15
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STARTING AND FUEL SHUTOFF CIRCUIT THEORY OF OPERATION
is energized by ground applied to terminal 2 of the
When key switch S1 is moved to START, power is
relay from pin 18 of monitor controller and display A5.
applied from key switch terminal ST to terminal e of
This prevents the starter motor from being activated if
starter relay K13 and terminal g of fuel shutoff relay
the key switch is moved to START while the engine is
K15, energizing both relays. (The ground path for the
running, by removing the ground path for starter relay
starter relay coil is provided through terminals 3 and 4
K13.
of de-energized starter protection relay (K11). Battery
power from alternator power fusible link F22 is applied
When star aid switch S18 is pressed, start aid relay
from terminals B and G of energized starter relay K13
K12 is energized by ground applied to terminal 2. With
to starter M1 solenoid terminal C, energizing the
relay K12 energized, power from start aid fuse F20 is
solenoid. This applies battery voltage at starter
applied to start aid solenoid Y4 through the energized
terminal B (from battery relay K14) to the motor
relay contacts, energizing the start aid solenoid. Start
winding, and the starter motor starts cranking the
aid solenoid diode V1 limits the voltage spikes
engine.
generated by the solenoid coil when it is de-energized.
At the same time, power from fuel shutoff fusible link
Start relay coil suppression diode V9 limits the voltage
F23 is applied through terminals B and G of the
spikes generated by the starter relay coil when the
energized fuel shutoff relay to the pull-in coil of fuel
relay de-energizes.
shutoff solenoid Y7, opening the fuel valve. Power
from power on 10-amp fuse F5 at the hold-in coil of
Fuel shutoff solenoid pull-in and hold-in coil
the fuel shutoff solenoid keeps the fuel valve open
suppression diodes V10 and V8 limit the voltage
after the key switch is returned to ON.
spikes generated by the solenoid coils when they are
de-energized.
When the engine is running and the alternator is
producing output voltage, starter protection relay K11
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