shape of a band broken by a triangular land that is the
Wobble Plate Pump System (Fig. 5-10).
same diameter as the ends of the valve. The reservoir
created by the reduced portion of the valve is connected
a. General System Operation. The wobble plate
to each pump cavity by individual ports so that the pump
pump system basically is the same as the multiple unit
cavities may be supplied with fuel.
injection system (para. 5-14).
The difference in the
receives a constant supply of low-pressure fuel from the
system lies in the injection pump. In a wobble plate
As with the multiple unit injection
pump, all of the pump plungers are actuated by a single
system, delivery pump pressure is regulated to
wobble plate instead of a camshaft that has a separate
approximately 15 psi (103.43 kPa).
cam for each pump plunger. Also, the metering of the
fuel is accomplished by a single axially located rotary
(3) The triangular land serves to consecutively
valve in the wobble plate unit, whereas the rotary
block each pump delivery port as it rotates. The
movement of the individual plungers controls the amount
triangular land is situated so that it will block each pump
of fuel in the multiple unit injection pump.
delivery port at the same time that the wobble plate is
moving the respective pump plunger at the maximum
b. Wobble Plate Pump Principles.
A plate is
speed through its delivery stroke. Fuel is delivered to
mounted on a shaft and set at an angle to it so that as
the fuel injector as long as the delivery port is blocked.
the shaft rotates, the plate moves laterally in relation to
any given point on either side of it. The pump derives its
(4) The rotational relationship of the rotary
name from the fact that the plate appears to wobble back
valve and the wobble plate causes each pump to deliver
and forth as it rotates.
The end of the push rod is
a fuel charge to its respective injector in turn as the
placed in a guide plate that lays against the wobble plate.
The pumps in the Injection unit are
The push rod is held in a bore in the pump body so that
connected to the fuel injectors to coincide with the firing
is can move only In a direction parallel to the wobble
order of the engine. The pump is gear driven by the
plate shaft. The rotation of the wobble plate then causes
engine at a speed of exactly one-half that of the
the guide plate to wobble, thus moving the push rod back
crankshaft. The end result will be the injection of fuel to
The push rod is connected to the pump
each cylinder at the beginning of each power stroke.
plunger so that movement to the left actuates the pump
on its delivery stroke and a spring returns it on the
(5) To obtain zero delivery, the valve is moved
endwise to a position where the delivery ports are never
blocked by the triangular land. When this occurs, the
c. The Wobble Plate Injection Pump. As stated
movement of the pump plungers merely causes the fuel
previously, the wobble plate injection pump contains an
to move back and forth in the delivery ports.
individual plunger-type pump for each cylinder.
results in zero delivery to the injectors due to insufficient
pump plungers are spaced equally about the wobble
pressure to open the spring-loaded delivery valves.
plate. As the wobble plate rotates, it will actuate all of
the individual Injection pumps. At any given time during
(6) To cause the pump to deliver fuel, the
rotation, half of the plungers will be moving on their
rotary valve is moved endwise so that the triangular land
delivery stroke while the other half will be on their return
begins to block the delivery ports. Due to the triangular
shape of the land, further endwise movement of the
rotary valve will in- crease the time that the port is
(1) The rotary metering valve is driven by the
blocked, increasing fuel delivery. The end result is that
same shaft that drives the wobble plate.
fuel delivery can be controlled by the endwise movement
valve consists of a lapped cylindrical shaft that is fitted
of the rotary valve. Endwise movement of the rotary
closely in a barrel to prevent fuel from escaping at its
valve is accomplished by the control lever. The position
ends. Fuel is admitted to the barrel at the center of the
of the control lever is determined by the governor (para
valve, which contains a spool like reduction In diameter.
This reduction in diameter acts as a fuel reservoir.
The reduced portion of the valve is in the