CHAPTER 3. REPAIR OF ENGINE COMPONENTS

TM 5-4320-258-34

CHAPTER 3

REPAIR OF ENGINE COMPONENTS

SECTION I. REPAIR OF FUEL SYSTEM COMPONENTS

3-1.

Description of Fuel System

against a dished race, forcing the race to move , axially

a. The fuel tank is bolted to the skid at the

away from the rotating balls. The movement of the

dished race is transferred to a drive fork through a thrust

radiator end of the engine. It is narrow enough to ride

bearing. The fork is pinned to the governing shaft which

between the longitudinal frame members of the skid. It

pivots as the drive fork moves. An external governing

has an offset to permit part of the tank to slide under the

.lever on the end of the control shaft is connected to the

radiator end of the engine. The tank capacity is 30

throttle control onthe carburetor and as the engine

gallons.

b. Fuel from the fuel tank is pumped to the

speed tends to increase, the throttle is closed slightly,

resulting in a decrease in engine speed. The decrease

carburetor by a fuel pump mounted on and driven by the

in engine speed decreases the centrifugal force of the

engine. The updraft-type carburetor controls the fuel-air

balls, and the dished race moves axially toward the

mixture which is fed to the engine to meet the needs of

balls. This movement is sensed by the fork which, in

the engine power requirements. A float system controls

turn, transfers the movement to the external governing

the level of the fuel in the carburetor float bowl.

lever.

The governing lever opens the carburetor

Adjustment screws are provided to permit regulation of

throttle, tending to speed up the engine. In this manner,

the high-speed operation fuel mixture, the idle mixture,

a balanced condition is reached and the engine speed

and the idle speed. Choking is controlled manually.

c. Engine speed control is done by the

remains constant, keeping the engine speed at the level

determined by the throttle control setting. Adjustment of

interoperation of the governor and the carburetor. The

the governor'is made by changing the tension of the

governor is a variable-speed type and is driven by the

spring which applies tension to the external governing

timing gear on the end of the camshaft. The driver on

lever and which tends to keep the dished race against

the drive shaft of the centrifugal flyball governor

the flyballs. Tightening the spring tends to raise engine

engages four hardened steel balls. As the engine runs,

speed at any particular throttle control setting.

centrifugal force tends to throw the balls outward. As

Decreasing spring tension lowers the speed.

the engine speed increases, the centrifugal force

increases. This causes the balls to exert pressure

3-1