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. 5-33 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