HEAD
HAND PRIMING
METERING
ROTOR
PORT
OUT LET
VALVE
DISCHARGE
FUEL
PORT
INLET
HAND
PRIMING
SPRING
DELIVERY
VALVE
ASf04042
DISCHARGE
FUEL
Figure 4-42.--Rotor in discharge position (DC pump).
ASf04044
OUTLET
Figure 4-44.--Regulating piston during hand priming.
head, at which time the rollers simultaneously contact
the opposing cam lobes. The cam lobes force the
are located on either side of the charging port of the
plungers toward each other, discharging the fuel from
rotor near its flange end. These grooves carry off fuel
the cylinder through the outlet port into the outlet
from the hydraulic head charging ports to the housing.
passage in the hydraulic head and the fuel injection line
This flow of fuel lubricates the cam, rollers, governor
connected to this passage (fig. 4-42). The cam is
parts, etc. The fuel flows through the entire pump
relieved to allow a slight outward movement of the
housing, absorbs heat, and is allowed to return to the
roller before the discharge port is closed off. This action
supply tank through a fuel return line connected to the
drops the pressure in the injection line enough to give
pump housing cover, thus providing for pump cooling.
sharp cutoff injection and prevent nozzle dribbling.
The end plate functions to provide passages for fuel
A displacement type delivery valve (fig. 4-42) is
and to cover and absorb end thrust of the transfer pump,
located in the drive passage of the rotor between the
to house the pressure regulator valve, and to house the
charging port and the discharge port of the rotor. It
priming bypass spring, which permits fuel to bypass the
remains closed during charging and opens under high
transfer pump during hand priming.
pressure as the plungers are forced together. Its purpose
is to aid, by injection line pressure relief, the cam
Figures 4-43, 4-44, and 4-45 show the regulating
"retraction" previously described. Two small grooves
piston in three positions: at rest, during hand priming,
and in operation. Figure 4-43 shows the piston covering
HAND PRIMING
PORT
REGULATING
FUEL
PORT
INLET
FUEL
SLEEVE
INLET
PRESSURE
PISTON
R E G U L AT I N G
AT
REST
PRIMING
BYPASS
REGULATING
SPRING
SPRINGS
FUEL
ASf04045
OUTLET
FUEL
ASf04043
OUTLET
Figure 4-45.--Regulating piston in pressure regulating
Figure 4-43.--Regulating piston at rest.
position.
4-33
