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FUEL SYSTEM
A. DESCRIPTION OF SYSTEM
The engine fuel system consists of a fuel tank, first
stage fuel filter, fuel transfer pump, second stage
fuel filter, fuel injection pump, fuel nozzles, and
the fuel· lines. There are two fuel pressure systems;
the low, pressure system and the high pressure
system.
The low pressure system consists of the fuel tank,
first stage fuel filter, fuel transfer pump, second
stage fuel filter, fuel leak-off header, and the fuel
return line leading from the fuel sump of the fuel
injection pump to the fuel tank.
The high pressure sy;~tem. consists of the fuel in-
.d!~!ion pump, fuel n~zzles, and aU high pressure
'• fpll'Jines connecting tlie fuel injectfor, pump to the
(uei no:µles. The high pressure fhel lin~s are
s~c:imles!i ste.el tubing and each line is. the same
l~ngth. These. lines being the same length assures
· thil$tQper timing and the proper amount of fuel
·tq~.ach fuel nozzle. These lines are not interchange-
·~i,fo;
when ordering lines· for· replacement, specify
,f\•,.:•.i
.,. \ .
/
'f9r
;~~ic;h cylit!d~r the line is ordered.
.
.
Tl,e,f~~Fis draWh from the fuel tank, through the
Ji:r~fstag(?. f~eF;filter, by the fuel transfer pump.
·The fuel tis th~n . forced by the transfer pump,
through the second stage }uel filter and to the fuel
inj~ction pump. The amount of fuel required for
~o,:nbustion. is forced under high pi:essure by the
fuel injection pump, through the high pressure fuel
FUEL PRESSURE RELIEF VALVE
ENGINE
lines to the fuel nozzles, from which the fuel enters
the engine combustion chambers in the form of a
fine cone-shaped spray.
There is a certain amount of fuel seepage between
the lapped surfaces of each fuel nozzle va.lve and
its body, which is necessary for lubrication. This
leakage of fuel accumulates around the spindle ·
and in the spring compartment of each fuel nozzle,
and is returned through the leak-off header to the
fuel return line, extending to the fuel tank. The
excess fuel delivered to the fuel injection pump by
the fuel transfer pump is returned to the fuel tank
through the fuel return line. A pressure of 5 to 15
P.S.I. is maintained within the low pressure fuel
system by a fuel pressure relief valve installed in
the fuel return outlet of the fuel injection pump.
The heavy-duty fuel injection pump is of the con-
stant-stroke, distributing-plunger, sleeve control
type, the plunger being actuated by a cam and
tappet arrangement which also carries the gearing
for the distribution function. Its purpose is to meter
the fuel accurately and deliver it precisely at a
definite moment in the engine cycle and under
high pressure to the fuel nozzles. The fuel injection
pump plunger is 9
M.M.
in diameter and the pump
is controlled by .a mechanical-centrifugal type
(type· "C'? governor).
The function of the fuel nozzles is to direct the
metered quantity of fuel, received from the fuel
injection pump, into the engine combustion cham-
TO FUEL PRESSURE GAGE
(SPECIAL EQUIPMENT)
r
1
1
SECOND ST AGE FUEL FILTER
FUEL TRANSFER
PUMP
FIRST STAGE FUEL FILTER
-
FUEL
TANK
Loo--------------
Fuel Flow -
Schematic
Diagram - - - - - - - - - - - - - - '
FIG. 11
.. 22
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