TM 55-1730-229-12
TO 35C2-3-473-1
SECTION XI.
MAINTENANCE OF FUEL SYSTEM
ter bypass valve (13). Fuel entering the fuel control unit
passes through the inlet filter (14) and to the high pres-
sists of: a fuel tank (4), a fuel filter (auxiliary) (9), a fuel
sure pump (16). Fuel leaving the pump branches to the
pump (auxiliary) (10), a fuel control unit (FCU) (20), a
metering valve (21), differential pressure valve (24), and
shutdown fuel solenoid (26), a fuel nozzle (28) and a
relief valve (23). The differential pressure valve main-
four-way fuel valve (35).
tains a constant pressure drop across the metering valve
a. Fuel Tank. The fuel tank (4) is fitted with a low
(21) so the flow is proportional to the valve area. Valve
fuel sensor (7) and a fuel level sensor (5). The low fuel
area is modulated by the torque motor (18) electrical sig-
sensor is electrically connected to an amber LOW FUEL
nal inputs from the electronic control unit (ECU). Fuel
indicator light of the control panel. The LOW FUEL indi-
flow passes from the metering valve and out the me-
cator illuminates when approximately 30 minutes of en-
tered fuel outlet (25) to the shutdown fuel solenoid (26).
gine operating time remains. The fuel level sensor is
electrically connected to a FUEL meter on the control
d. Shutdown Fuel Solenoid. The shutdown fuel
panel.
solenoid (26) controls the flow (on/off) of fuel to the fuel
nozzle. The solenoid is normally closed (n.c.) with no
a.1. Four-way Fuel Valve. The fourway fuel
+28 vdc power applied, shutting off fuel to the fuel noz-
valve (35) enables an external fuel source to be con-
zle. The solenoid is controlled by the electronic con-
nected to AGPU for operation of the engine. Three of
trol unit (ECU). During engine start/run operations, the
the four valve positions are used, the fourth position
ECU applies +28 vdc to open the fuel solenoid when
is blanked. The four-way valve also acts as a shut-off
the engine reaches 10% speed, and maintains the volt-
cock isolating the engine from the fuel source.
age during normal engine operation. Removing +28 vdc
from the fuel solenoid is the only way to immediately shut
b. Auxiliary Fuel Pump and Filter. The auxiliary
down engine, since the engine requires no ignition once
fuel pump (10) is activated by +28 vdc (battery voltage)
it reaches governed (100%) speed. The fuel solenoid is
when the GTE ENGINE CONTROL switch on control
closed by removal of +28 vdc by any one (or combina-
panel is set to START (and RUN) position. The fuel
tion of ) the following conditions:
pump draws fuel from the tank through an auxiliary filter
(9), and provides low pressure fuel to the fuel control
switch
(1)
EMERG
STOP
pushbutton
unit (FCU) (20).
pressed.
c. Fuel Control Unit (FCU). The fuel control unit
(2)
Control panel MASTER SWITCH set to
(20 is mounted on the front of the gearcase oil pump
OFF.
housing assembly. The fuel control unit consists of a
fuel inlet filter (14), high pressure pump (16), strainer el-
(3)
Control panel ENGINE CONTROL switch
ement (17), torque motor (18), metering valve (21), re-
set to OFF (normal method of engine shutdown).
lief valve (23), differential pressure valve (24), and a fil-
