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 spring housing. 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.

NOTE Before performing any adjustments or repairs to the governor, it is recommended that you consult the manufacturer's service manual.

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 systems.

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