TM 5-3805-260-24
Constant bleed valve (4) lets approximately 9 gallons of
fuel per hour go back to fuel tank (7). This fuel goes
back to fuel tank (7) through return line for constant
bleed valve (3). This flow of fuel removes air from
housing (14) and also helps to cool the fuel injection
pump. Check valve (D) makes a restriction in this flow of
fuel until the pressure in housing (14) is 8 3 psi (55
20 kPa).
OPERATION OF FUEL INJECTION PUMPS
The main components of a fuel injection pump in the
sleeve metering fuel system are barrel (A), plunger (B),
and sleeve (D). Plunger (B) moves up and down inside
the barrel (A) and sleeve (D). Barrel (A) is stationary
while sleeve (D) is moved up and down on plunger (B) to
make a change in the amount of fuel for injection. When
the engine is running, fuel under pressure from the fuel
transfer pump goes in the center of plunger (B) through
fuel inlet (C) during the down stroke of plunger (B). Fuel
can not go through fuel outlet (E) at this time because it
is stopped by sleeve (D), (see position 1). Fuel injection
starts (see position 2) when plunger (B) is lifted up in
barrel (A) enough to close fuel inlet (C). There is an
increase in fuel pressure above plunger (B), when the
plunger is lifted by camshaft (4). The fuel above plunger
(B) is injected in to the engine cylinder.
FUEL INJECTION SEQUENCE
1, 2, 3. Injection stroke (positions) of a fuel
injection pump. 4. Injection pump camshaft. A.
Barrel. B. Plunger. C. Fuel inlet. D. Sleeve. E.
Fuel
outlet.
F.
Lifter.
Injection will stop (see position 3) when fuel outlet (E) is
lifted above the top edge of sleeve (D) by camshaft (4).
This movement lets the fuel that is above, and In,
plunger (B) go through fuel outlet (E) and return to the
fuel injection pump housing.
When the sleeve (D) is raised on plunger (B), fuel outlet
(E) is covered for a longer time, causing more fuel to be
injected in the engine cylinders. If sleeve (D) is low on
plunger (B), fuel outlet (F.) is covered for a shorter time,
causing less fuel to be injected.
OPERATION OF FUEL INJECTION NOZZLE
The fuel inlet (6) and nozzle tip (13)re parts of the nozzle
body,
(11). Valve (8) is held in position by spring force
Force of the spring is controlled by pressure
adjustment screw (3). Locknut (4-) holds pressure
adjustment screw (3) in position. The lift of value (8) is
controlled 1b lift adjustment screw (2).Locknut (10)
holds lift adjustment screw (2) in position. Compression
seal (7) goes on nozzle body (11). The compression
seal goes against inlet fitting (6) and prevents the
leakage of compression from the cylinder. Carbon dam
(12), at the lower end of nozzle body (11), prevents the
deposit of carbon in the bore in the cylinder head.
FUEL INJECTION NOZZLE
1. Cap. 2. Lift adjustment screw. 3. Pressure
adjustment screw. 4. Locknut for pressure
adjustment screw. 5. O-ring seal. 6. Fuel inlet. 7.
Compression seal. 8. Valve. 9. Orifices (four). 10.
Locknut for lift adjustment screw. 11. Nozzle body.
12. Carbon dam. 13. Nozzle tip.
Fuel, under high pressure from the fuel injection pump
goes through the hole in fuel inlet (6). Tile fuel then goes
around valve (8), fills the inside of nozzle body (11) and
pushes against the valve guide. When the force made
by the pressure of the fuel is more than the force of the
spring, valve (8) will lift. When valve (8) lifts, fuel under
light pressure will go through the four .0128 in. (0.325
mm) orifices (9) into the cylinder. When the fuel is sent
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