PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 2/TASK 2
the governor spring to control the quantity of fuel rather than operating
the fuel control rod directly. The fuel delivery control system of the
injection pump is connected to the governor yoke in such a manner that any
movement of the yoke will directly affect the quantity of the fuel injected.
The spring tension is controlled by the operating lever, the movement of
which is determined by the position of the foot throttle. The travel of the
operating lever is limited by the idle and maximumspeed screws. When the
weights are fully collapsed (engine stopped), the spring moves the sliding
sleeve and yoke so that the fuel injection pump is in the fullfuel
position. When the weights are fully extended, the sliding sleeve and the
yoke move to the rear and decrease the amount of fuel delivery.
(3) If the load on the engine is decreased, the engine tends to
accelerate, However, when the engine does accelerate, the increased
centrifugal force causes the governor flyweights to move outward, resulting
in the movement of the fuel control rod through the governor sleeve toward
the nofuel position. This will cause an equilibrium to develop between the
flyweights and the governor spring. The movement of the operating lever
varies the spring tension. This will cause a change in the point of
equilibrium between the spring and the flyweights, effectively changing the
engine speed for any given load.
(4) To accelerate the vehicle with a given load, the foot throttle is
depressed, which in turn increases the governor spring tension. The
increase in tension causes the governor sleeve to move the control rod
through the yoke toward the fullfuel position. As engine speed increases,
the flyweights will move outward until they reach the point of equilibrium
with the governor spring. At this point, engine speed will stabilize.
d. Vacuum Governor (figure 59 on the following page).
(1) The vacuum governor operates by employing pressure drop, created
by the velocity of the air passing through a venturi located in the air
intake manifold. The governor consists essentially of an atmospheric
suspended diaphragm connected by linkage to the control rod of the injection