TM 55-1930-209-14&P-21
Section X. Fuel Pump and Fuel Filters
5-36 General
a.
The fuel pump (Figure 5-15) is a positive displacement gear type. The pump circulates or transfers fuel from fuel
tank to fuel injectors. The pump circulates excess supply of fuel through fuel injectors and through an aspirator valve to
supply fluid for torque converter. The unused fuel returns to fuel tank.
b.
The fuel pump body and cover are positioned by means of two dowels. The dowels aid in maintaining gear shaft
alignment. The mating surfaces of pump body and cover are ground perfectly flat. No-gasket is used between cover
and body since pump clearances are set up on a metal-to-metal contact basis. A very thin coating of sealant provides a
seal against any irregularities in mating surfaces.
c.
A spring-loaded relief valve incorporated in pump body normally remains in closed position, operating only when
pressure on outlet side (to fuel filter) reaches approximately 65 psi.
d.
The fuel pump draws fuel from fuel tank through strainer, and forces it under pressure through fuel filter. From
filter, fuel is forced through fuel inlet passage in cylinder head and fuel lines into fuel injectors.
e.
Fuel passes through a filter element within fuel injector to a chamber where it is metered, displaced, and
atomized through spray tip into the combustion chamber.
f.
Heat, generated during high compression of the air, ignites fine fuel spray and combustion continues until fuel is
burned.
g.
Fuel in excess of that required for engine operation is circulated through injectors by fuel pump and serves as a
coolant. In addition to serving as a coolant, circulation of surplus fuel bleeds any air or vapor in system back to fuel tank
where it is vented to atmosphere. Surplus fuel leaving injectors flows through outlet fuel line to fuel return passage and
then through a restricted fitting and a tube back to fuel tank.
5-37 Fuel pump removal and disassembly
a.
Removal. Remove fuel pump assembly as illustrated in Figure 5-15.
b.
Disassembly
(1)
Disassemble fuel pump in numerical sequence as illustrated in Figure 5-16.
(2)
Remove drive shaft, drive gear, and retaining ball as an assembly.
(3)
Press drive shaft through gear far enough to remove ball. Then invert shaft and gear assembly and press
the shaft from gear. Do not press square end of shaft through gear.
(4)
If oil seals need replacing, remove them as illustrated in Figure 5-17. Clamp pump body in a bench vise
and screw threaded end of removal tool shaft into outer oil seal (seal nearest bolt flange). Tap pilot end of tool and
remove seal. Repeat this operation on inner seal.
5-44
