DETROIT DIESEL 53
FUEL INJECTOR (NEEDLE VALVE)
The fuel injector (Fig 1.) is a lightweight compact unit
which enables quick. easy starting directly on diesel
fuel and permits the use of a simple open type
operation provides for simplified controls and easy
adjustment. No high pressure fuel lines or complicated
air-fuel mixing or vaporizing devices are required.
The fuel injector performs four functions:
Creates the high fuel pressure required for
Meters and injects the exact amount of fuel
Fig. 2. - Fuel Metering from No-Load to Full
required to handle the load.
Atomizes the fuel for mixing with the air in the
quantity of accurately metered and finely atomized fuel
oil into the cylinder.
Permits continuous fuel flow.
Metering of the fuel is accomplished by an upper and
lower helix machined in the lower end of the injector
Combustion required for satisfactory engine operation Is
plunger. Figure 2 illustrates the fuel metering from no-
obtained by injecting under pressure, a small
load to full-load by rotation of the plunger in the bushing.
Figure 3 illustrates the phases of injector operation by
the vertical travel of the injector plunger.
The continuous fuel flow through the injector serves, in
addition to preventing air pockets in the fuel system, as
a coolant for those injector parts subjected to high
To vary the power output of the engine, injectors having
different fuel output capacities are used. The fuel
output of the various injectors is governed by the
Fig. 3.- Phases of Injector Operation Through
Vertical Travel of Plunger
Fig. 1. - Fuel Injector Assembly
1972 General Motors Corp.
SEC. 2.1.1 Page 1