TM 5-3895-359-14&P
A pressure relief passage has been provided in the
spring cage to permit bleed-off of fuel leaking past the
needle pilot in the tip assembly.
From this no injection position to full injection position
(full rack movement), the contour of the upper helix
A check valve, directly below the bushing, prevents
advances the closing of the ports and the beginning of
leakage from the combustion chamber into the fuel
injection.
injector in case the valve is accidentally held open by a
small particle of dirt. The injector plunger is then
General Instructions for Injector Care and Overhaul
returned to its original position by the injector follower
The fuel injector is one of the most important and
spring. Figure 4 shows the various phases of injector
precisely built parts of the engine. The injection of the
operation by the vertical travel of the injector plunger.
correct amount of fuel into the combustion chamber at
On the return upward movement of the plunger, the high
exactly the right time depends upon this unit. Because
pressure cylinder within the bushing is again filled with
the injector operates against high compression pressure
fuel oil through the ports. The constant circulation of
in the combustion chamber, efficient operation demands
fresh cool fuel through the injector renews the fuel
that the injector assembly is maintained in first-class
supply in the chamber, helps cool the injector and also
condition at all times. Proper maintenance of the fuel
effectively removes all traces of air which might
system and the use of the recommended type fuel filters
otherwise accumulate in the system and interfere with
and clean water-free fuel are the keys to trouble-free
accurate metering of the fuel. The fuel injector outlet
operation of the injectors.
opening, through which the excess fuel oil returns to the
Due to the close tolerances of various injector parts,
fuel return manifold and then back to the fuel tank, is
extreme cleanliness and strict adherence to service
directly adjacent to the inlet opening.
instructions is required.
Changing the position of the helices, by rotating the
Perform all injector repairs in a clean, well lighted room
plunger, retards or advances the closing of the ports and
with a dust free atmosphere. An ideal injector room is
the beginning and ending of the injection period. At the
slightly pressurized by means of an electric fan which
same time, it increases or decreases the amount of fuel
draws air into the room through a filter. This pressure
injected into the cylinder. Figure 3 shows the various
prevents particles of dirt and dust from entering the
plunger positions from no-load to full-load. With the
room through the doors and windows. A suitable air
control rack pulled out all the way (no injection), the
outlet will remove solvent fumes along with the outgoing
upper port is not closed by the helix until after the lower
air. Also provide a source for 110 volt alternating
port is uncovered. Consequently, with the rack in this
current electric power.
position, all of the fuel is forced back into the supply
chamber and no injection of fuel takes place. With the
Provide the injector repair room with a supply of filtered,
control rack pushed all the way in (full injection), the
moisture-proof compressed air for drying the injector
upper port is closed shortly after the lower port has been
parts after they have been cleaned. Use wash pans of
covered, thus producing a maximum effective stroke
rust-proof material and deep enough to permit
and maximum injection.
Fig. 9. Removing Injector Follower Stop Pin
Fig. 8. Checking Rack and Plunger for Free
Movement with J 22396
10-3-5
