FUEL SYSTEM OPERATION

TM 9-2320-386-10

1-20. FUEL SYSTEM OPERATION

A mechanical governor, transfer pump, and high-pressure unit injection fuel sys-

tem provide engine response and fuel economy for ESP vehicles.

The transfer pump creates a vacuum that draws fuel from the fuel tank. It then

pumps fuel under low pressure to the fuel/water separator where water and contam-

inants are removed. Filtered fuel is then carried to the injectors. The injectors use a

plunger-and-barrel system to create the high pressures needed for injection. Inside

the injector, a spring-loaded needle valve lifts from its seat to allow high pressure

fuel to be injected into each cylinder. Excess fuel is routed from the engine cylinder

head back to the governor and then to the fuel tank. A fuel shutoff solenoid mounted

on the fuel pump cuts the flow of fuel to the injectors when the operator turns the

accessory switch off.

1-20.1. COMPRESSED AIR SYSTEM OPERATION

The ESP vehicles are equipped with a compressed air system that supplies clean

dry filtered air to operate air-actuated or assisted accessories throughout the vehi-

cle.

The air is supplied from engine air compressor through an air dryer and stored in

two air reservoirs.

The air from reservoirs is piped along frame rails back to two rear couplings. The

left side air coupling is the service coupling and is used to supply air to operate

trailer brakes. The right side air coupling is the emergency coupling and is used to

release spring brakes if trailer is so equipped and to connect an air hose to manual-

ly inflate vehicle tires.

The air reservoirs also supply air forward to air pressure gauge, two air hydraulic

brake boosters, steering assist cylinder, drag link assist, air horns, transfer case air

cylinder, front axle engagement switch, and cooling fan actuator and clutch.

1-21. CENTRAL TIRE INFLATION SYSTEM (CTIS) OPERATION

The CTIS allows the operator to manually select a tire pressure suitable to the

terrain being traversed. The system incorporates an Electronic Control Unit (ECU)

and air regulating system which provides and maintains the correct air pressure to

all tires at the same time. The ECU controls the manifold, which automatically

directs compressed air to inflate the tires, or signals the deflation port to deflate the

tires according to the operator-selected terrain setting. The ECU monitors and regu-

lates air system pressure in 30-minute intervals and compensates for thermal tire

pressure changes as recommended by the tire manufacturer.

Change 1

1-14.1