state of balance can exist. If, however, the load is
increased or decreased, a corrective action will be
initiated. The bell crank lever and pivoting differential
lever will be moved by the action of the governor spring
or weights to reestablish a state of balance.
Remember the governor can only react and change
to the rpm of the engine.
The variable speed mechanical governor is readily
identifiable from the limiting speed governor by the fact
that it has only one lever on the top of the governor
cover, which is the stop/run lever. The speed control
lever is located vertically on the end of the governor
A large booster spring is attached
between the speed control lever and a bracket on the
cylinder head, used to assist the operator in overcoming
governor resistance during throttle movement. The
letters SWVS (single-weight variable speed) are
stamped on the governor identification plate.
Before performing any adjustments or
repairs to the governor, it is recommended that
you consult the manufacturers service
Figure 5-28.Pressure-time fuel system.
CUMMINS DIESEL FUEL SYSTEMS
Over the years Cummins has produced a series of
innovations, such as the first automotive diesel, in
addition to being the first to use supercharging and then
turbocharging. All cylinders are commonly served
through a low-pressure fuel line. The camshaft control
of the mechanical injector controls the timing of
injection throughout the operating range. This design
eliminates the timing-lag problems of high-pressure
To meet Environmental Protection Agency (EPA)
exhaust emissions standards, Cummins offers the
Celect (electronically controlled injection) system.
Since the Celect system did not start production until
1989, there are literally thousands of Cummins with
pressure-time (PT) fuel systems. We will discuss the
operation of the PT system first, then discuss the basic
operating concept of the Celect system.
Pressure-Time Fuel System
The pressure-time (PT) fuel system (fig. 5-28) is
exclusive to Cummins diesel engines; it uses injectors
that meter and injects the fuel with this metering based