two pumping plungers located in the pumping cylinder.
Slots in the rear of the rotor provide a place for two
spring-loaded transfer pump blades. In the rotor, the
shoe, which provides a large bearing surface for the
roller, is carried in guide slots. The rotor shaft rotates
with a very close fit in the hydraulic head. A passage
through the center of the rotor shaft connects the
pumping cylinder with one charging port and one
discharging port The hydraulic head in which the rotor
turns has a number of charging and discharging port,
based on the number of engine cylinders. An eight-
cylinder engine will have eight charging and eight
discharging ports. The governor weight retainer is
supported on the forwarded end of the rotor.
TRANSFER PUMP (fig. 5-14)The transfer
pump is a positive displacement, vane-style unit,
4. Inlet strainer.
2. Transfer pump liner.
3. End plate adjusting
6. Regulating piston.
7. End plate plug.
Figure 5-14.Transfer pump.
consisting of a stationary liner with spring-loaded
blades that ride in slots at the end of the rotor shaft. The
delivery capacity of the transfer pump is capable of
exceeding both pressure and volume requirements of
the engine, with both varying in proportion to engine
speed. A pressure regulator valve in the pump end plate
controls fuel pressure. A large percentage of the fuel
from the pump is bypassed through the regulating valve
to the inlet side of the pump. The quantity and pressure
of the fuel bypassed increases, as pump speed increases.
The operation of the model DB2 injection is similar
to that of an ignition distributor. However, instead of the
ignition rotor distributing high-voltage sparks to each
cylinder in firing order, the DB2 pump distributes
pressurized diesel fuel as two passages align during the
rotation of the pump rotor, also in firing order. The basic
fuel flow is as follows:
Fuel is drawn from the fuel tank by a fuel lift
pump (mechanical or electrical) through the
primary and secondary filters before entering the
As fuel enters the transfer pump, it passes
through a cone-type filter and on into the
hydraulic head assembly of the injection pump.
Fuel under pressure is also directed against a
pressure regulator assembly, where it is
bypassed back to the suction side should the
pressure exceed that of the regulator spring.
Fuel under transfer pump pressure is also
directed to and through a ball-check valve
assembly and against an automatic advance
Pressurized fuel is also routed from the hydraulic
head to a vent passage leading to the governor
linkage area, allowing any air and a small
quantity of fuel to return to the fuel tank through
a return line which self-bleeds air from the
system. Fuel that passes into the governor
linkage compartment is sufficient to fill it and
lubricate the internal parts.
Fuel leaving the hydraulic head is directed to the
metering valve, which is controlled by the
operator throttle position and governor action.
This valve controls the amount of fuel that will
be allowed to flow on into the charging ring and