Figure 5-24.-End of fuel delivery flow diagram.
The plunger is designed to operate at crankshaft
speed on four-cycle engines. It is actuated by a camshaft
and tappet arrangement. The pump camshaft, which also
includes the gearing for fuel distribution, is supported
on the governor end by a bushing-type bearing and by a
ball roller bearing on the driven end. An integral
mechanical centrifugal governor (fig. 5-25) driven
directly from the pump camshaft without gearing
controls fuel delivery in relation to engine speed. This
pump has a smoke limit cam within the governor
housing to help control the exhaust smoke of various
fuels. The mechanical centrifugal advance unit of this
pump provides up to 9-degrees advance timing and is
driven clockwise at crankshaft speed.
Table 5-2 lists the most common malfunctions and
the probable causes. Further tests, adjustments, and
specifications are available through the manufacturers
manual which you should use for repairs or adjustments.
Types of Nozzles
Bosch nozzles are inward opening with a multiple
orifice and a hydraulically operated nozzle valve. The
two models of this nozzle in use are the American Bosch
and the Robert Bosch. They may be easily identified by
either the length of the nozzle tip holding nut or the
nozzle drilling code on the smaller diameter of the
nozzle valve body. The American Bosch nozzle nut is
3 inches long, and the nozzle tip has a hand-printed
drilling code. The Robert Bosch nozzle nut is 2 inches
Figure 5-25.-Governorsectional view.
long, and the nozzle tip has a machine-etched drilling
code. Figure 5-26 shows a view of the nozzle and
identifies the various component parts. Component
parts, although similar, are not interchangeable between
the two nozzles.
Figure 5-26.-Bosch nozzle nomenclature.