Section IX. MAINTENANCE OF FUEL SYSTEM
4-18. DESCRIPTION AND FUNCTION.
a. Low Pressure System (see Schematic figure
(1) Fuel pump may draw fuel from an external
source to fill set tank or set tank may be filled man-
ually. If an external fuel source is selected, a float
valve assembly in the set tank maintains the fuel
level in the tank. Two other fuel pumps (in series)
draw fuel from the set tank and force the fuel through
a primary strainer, two filters, and a check valve
assembly, to the injection pump.
b. High Pressure System.
(1) Fuel injection pump forces the fuel, under
high pressure, to the fuel injection nozzles. The in-
jection nozzles provide fuel to each combustion
chamber of the engine. Unused fuel is returned from
the injectors to the fuel tank. A cam and gear on the
camshaft drives the fuel injection pump. The gear
drives the pump face gear, providing fuel distribution
to each cylinder in the proper order. The cam oper-
ates the pump plunger, pressurizing fuel to the noz-
zles. A control sleeve meters fuel by controlling the
length of time the plunger spill port is closed, main-
taining pressure, and therefore, the amount of fuel
delivered in each stroke. The pintle type injection
nozzles are conventional inward opening with ad-
justable opening pressure. They are factory adjusted
to open at 1900 to 1950 psi.
4-19. FUEL TANK ASSEMBLY<
a. Inspection on Equipment. Refer to paragraph
b. Removal (see figure 4-7). Drain fuel into suitable container
by opening drain valve. Tag and disconnect fuel hoses from fuel
tank fittings. Disconnect electrical lead from electrical connector
(10). Remove nut (1) and flatwasher (2) from straps (3) on out-
side of fuel tank. Remove tank from skid-base. On ASK equipped
generators, remove top panel, left panel and side closure assem-
blies (para. 5-4 and 5-5).
(1) Fuel Level Gage. Unscrew and remove fuel
level gage (5) using tools only on the hex portion of
(2) Float Switch. Unscrew collar and disconnect
electrical connector (10) if not previously discon-
nected. Unscrew and remove float switch (6) using
tools only on the square portions of the switch.
(3) Unscrew and remove fittings (7).
(4) Holding pipe adapter (11) with a wrench, un-
screw and remove drain valve (8).
(5) Loosen filler cap and remove filler cap (4) and
d. Cleaning and Inspection.
(1) Tank. Clean tank exterior using suitable sol-
vent and clean cloth and brush. Inspect tank for
signs of physical damage. If damaged refer to higher
level of maintenance.
(2) Fuel Level Gage. Check that fuel level gage
face is clean and readable. Check that as cork float
is moved up and down, the meter movement rotates.
(3) Float Switch. Inspect terminal connector for
damage to threads. Check to see that float slides on
shaft without binding. Clean with suitable solvent if
(4) Fittings. Inspect fittings for good leak-free
seating on tank and check threads for physical damage.
(5) Fuel Drain Valve Assembly. Check that drain
valve does not leak and threads for physical damage.
(6) Strainer. Invert and clean with solvent.
(1) Float Switch. Remove float switch (6) from
tank (9). Using an ohmmeter, check for continuity
between terminals A and B of switch (see figure
4-8). Switch should show no continuity when float is
up. Switch should close when float drops to 2-7/8
±3/16 inch from threaded collar of float switch. Re-
place switch if it does not operate properly.
(2) Tank. If tank shows signs of physical dam-
age or leaks refer to higher level of maintenance.
f. Reassembly (see figure 4-7).
(1) Fuel Drain, Valve. Engage threads of fuel
drain valve assembly (8) 1/2 turn into fuel tank
adapter (11). Coat threads with sealing compound
ML-S-22473. Tighten valve assembly Into adapter
(2) Fittings. Engage threads of fitting (7) 1/2 turn
into fuel tank (9). Coat threads with sealing com-
pound MIL-S-22473. Tighten fittings into tank. Fit-
tings should face Generator Set for proper connection
of fuel lines. Attach fuel lines to fittings.
(3) Float Switch. Engage threads of float switch
(6) 1/2 turn into tank (9). Coat threads with sealing
compound ML-S 22473. Tighten float switch (6) into
tank using tools only on square portion of switch. At-
tach electrical lead to connector (10) on top of float
switch and tighten.