Figure 1-29. Fuel density compensator (code A, B, C, D and E) sectional view.

TM 9-2910-226-34

c. The fuel supply is admitted to a pressure

regulating valve where the supply pressure is

reduced to a constant regulated pressure over the

engine operating speed and load range. Fuel flows

through the first (viscosity/density sensitive) an-

nular orifice formed by a close fitting piston in a

cylinder. From the servo pressure cylinder the fuel

flows to the second orifice which is a sharp-edged,

adjustable needle valve. The two orifices working at

widely different restrictions to the flow of fuel form a

system sensitive to viscosity changes. The pressure

difference between the two orifices will change the

servo pressure in direct relationship to the viscosity

of the fuel flowing. The position of the spring-loaded

servo diaphragm (fig. 1-28) or servo piston (fig. 1-29)

is varied in accordance with these servo pressure

drops.

Figure 1-28. Fuel density compensator (early code F),

sectional view.

Figure 1-29. Fuel density compensator (code A, B, C, D and E) sectional view.

1-30