Timing Advancement.

TM 9-2910-226-34

assembly. This position represents maximum fuel

plunger sleeve toward increased fuel delivery. The

limiting effect. In the low-idle position, pin (N) has

engine then increases to original speed. -

contacted surface (P), and raised the torque link

f. If engine load is decreased, the speed will

assembly. This provides maximum fuel delivery for

momentarily increase and the governor weights will

engine starting. The purpose of above operations is

move further out. The fingers on the weights shift

to protect the engine and automatic transmission

the sliding sleeve against the opposing spring forces.

from excessive load changes during shifting, while

The fulcrum lever shifts and moves the plunger

maintaining power at full load and providing suf-

sleeve toward decreased fuel delivery, reducing

ficient starting fuel quantities.

engine speed.

g. The operating shaft is connected to the fulcrum

1-26. Timing Advancement.

lever by the shaft spring plate (C) and operating

NOTE

shaft spring (D). The fork on the upper portion of the

The key letters shown below in parentheses

shaft spring plate engages the fulcrum lever. The

refer to figure 1-16.

operating shaft spring grips the tang on the spring

As the engine speed rotates the weight and spider

plate and the tang on the operating shaft. This

assembly (AH), centrifugal force opens the

torsion spring loads both tangs toward each other so

flyweights from. their collapsed position. The loading

that normally the operating lever and fulcrum lever

of the three timing device springs (B) acts against

act as though rigidly attached. When engine speed

the flyweights until a certain engine speed is

differs as a result of load changes, from the normal to

reached, at which point the forces of springs and

the operating lever position, the tangs part

flyweights are balanced. As engine speed increases,

momentarily until the governor senses the change.

the flyweights swing out and force the sliding gear

This function protects- the governor and fuel in-

(A) toward the timing device hub (C). As a result of

jection pump parts from unnecessary high loads and

this longitudinal and axial movement of the sliding

stresses.

gear, the metering and distributing pump camshaft

NOTE

is rotated slightly out of phase and in advance of the

The key letters shown below in parentheses

weight and spider. The axial movement of the sliding

refer to figure 1-18.

gear is caused by the internal helical splines of the

The functioning of the torque link assembly applies

sliding gear acting on the external helical splines of

only to code A-injection pumps. As the torque link

the weight and spider and the timing device hub

(D) moves upward, the fuel stop wedge (F) moves

(para 1-16). Therefore, the timing of the fuel pump

upward to an increased fuel delivery. `As it moves

with relation to the top dead center position of the

downward the fuel delivery decreases.

engine's piston is advanced within a given range.

h. The principle function of the torque link

assembly is to control the sliding stop wedge (F) and

1-27. Fuel Density Compensating (Typical). a. The

its movement up and down. Due to its wedge con-

multifuel engine operates on fuels having a

figuration, as it moves up it moves the stop plate (H)

significant variation in density and heat value per

forward allowing the smoke limit cam (G) to move to

gallon. These variations in the fuels affect engine

an increased fuel position. As it moves downward it

output. Any power loss due to a change of fuel is not

moves the stop plate toward the rear of governor

acceptable. The fuel density compensator on the fuel

housing or a decreased fuel position. The torque link

injection pump automatically varies the quantity of

assembly limits maximum fuel quantity at any

fuel delivered to the engine to maintain a constant

position of the operating shaft assembly other than

maximum power output regardless of the fuel being

the full-load position or low-idle position of the

used.

operating shaft assembly.

b. The characteristics of the fuels used in the en-

i. When the operating shaft assembly is in the

gine show a definite relationship between viscosity

full-load position the torque link assembly is in the

and heating value. The fuel density compensator

full-load quantity position. Pin (K) has contacted

takes this into consideration by making the viscosity

surface (L) of kidney slot and raised the torque link

characteristic a sensed variable. In the compensator

assembly to its maximum upward travel position.

the fuel is passed in series through two orificies of

As the operating shaft assembly is moved away from

widely different flow characterist its. A change in

the full-load position the torque link assembly moves

viscosity of the fuel flowing through these orifices

downward resulting in decreased fuel. At an in-

causes a pressure drop change which moves a servo

termediate operating shaft position, the spring (C)

diaphragm (fig. 1-28) or piston (fig. 1-29) to vary the

moves stop wedge (F) downward to a position where

full-load stop of the fuel injection pump.

both pins- come in contact with the torque link

1-29