TM 5-3895-359-14&P
injectors with other types of injectors
in an engine.
Each fuel injector has a circular disc pressed into a
recess at the front side of the injector body for
identification purposes (Fig. 5). The identification tag
indicates the nominal output of the injector in cubic
millimeters.
Each injector control rack (Fig. 2) is actuated by a lever
on the injector control tube which, in turn, is connected
to the governor by means of a fuel rod. These levers
can be adjusted independently on the control tube, thus
Fig. 3 Fuel Metering from No-Load to Full-Load
permitting a uniform setting of all injector racks.
The fuel injector combines in a single unit all of the parts
necessary to provide complete and independent fuel
injection at each cylinder.
Operation
the vertical travel of the injector plunger.
Fuel, under pressure, enters the injector at the inlet side
The continuous fuel flow through the injector serves, in
through a filter cap and filter (Fig. 2). From the filter,
addition to preventing air pockets in. the fuel system, as
the fuel passes through a drilled passage into the supply
a coolant for those injector parts subjected to high
chamber, that area between the plunger bushing and the
combustion temperatures.
spill deflector, in addition to that area under the injector
plunger within the bushing. The plunger operates up
Since the helix angle on the plunger determines the
and down in the bushing, the bore of which is open to
output and operating characteristics of a particular type
the fuel supply in the annular chamber by two funnel-
of injector, it is imperative that the correct injectors are
shaped ports in the plunger bushing.
used for each engine application. If injectors of different
types are mixed, erratic operation will result and may
The motion of the injector rocker arm is transmitted to
cause serious damage to the engine or to the equipment
the plunger by the follower which bears against the
which it powers.
follower spring (Fig. 6). In addition to the reciprocating
motion, the plunger can be rotated, during operation,
NOTE:
Do not intermix the needle
around its axis by the gear which meshes with the
valve
control rack. For metering the fuel, an upper helix and a
lower helix are machined in the lower part of the
plunger. The relation of the helices to the two ports
changes with the rotation of the plunger.
As the plunger moves downward, under pressure of the
injector rocker arm, a portion of that fuel trapped under
the plunger is displaced into the supply chamber through
the lower port until the port is closed off by the lower end
of the plunger. A portion of the fuel trapped below the
plunger is then forced up through a central passage in
the plunger into the fuel metering recess and into the
supply chamber through the upper port until that port is
closed off by the upper helix of the plunger. With the
upper and lower ports both closed off, the remaining fuel
under the plunger is subjected to increased pressure by
Fig. 4. Phases of Injector Operation Through
the continued downward movement of the plunger.
Vertical Travel of Plunger
When sufficient pressure is built up, it opens the flat,
non-return check valve. The fuel in the check valve
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