Vacuum Governor (figure 59 on the following page).

Principles of Gasoline And Diesel Fuel Systems
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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 maximum-speed 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 full-fuel

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 no-fuel 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 full-fuel 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

pump.

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