3-147. FUEL INJECTOR - MAINTENANCE INSTRUCTIONS.
a. The fuel injector is a lightweight, compact unit which enables quick, easy starting directly on diesel fuel and
permits the use of a simple, open-type combustion chamber. The simplicity of design and operation provides for
simplified controls and easy adjustment.
b. The fuel injector performs four functions:
(1) Creates the high fuel pressure required for efficient injection.
(2) Meters and injects the exact amount of fuel required to
handle the load.
(3) Atomizes the fuel for mixing with the air in the combustion chamber.
(4) Permits continuous fuel flow.
c. Combustion required for satisfactory engine operation is obtained by injecting, under pressure, a small quantity of
accurately metered and finely atomized fuel oil into the cylinder.
d. The continuous fuel flow through the injector provides:
Prevention of air pockets in the fuel system.
A coolant for those injector parts subjected to high combustion temperatures.
Do not intermix the needle valve injectors with the other types of injectors in an engine.
e. Each fuel injector has a circular disc pressed into a recess at the front side of the injector body for identification
purposes. The identification tag indicates the nominal output of the injector in cubic millimeters.
f. Fuel under pressure enters the injector from a fuel manifold. Motion of the rocker arm allows the injector to release
a spray of fuel into a cylinder. A control rack on the side of the injector controls the amount of fuel being dispensed, and
the speed of the engine. The injector control rack 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
permitting a uniform setting of all injector racks. Excess fuel exits the injector and is returned to a fuel manifold. The fuel
then returns to the fuel tank.