Section II. THEORY OF OPERATION - TM-9-2320-386-24-1-10050

TM 9-2320-386-24-1-1

0005 00

DESCRIPTION AND THEORY OF OPERATION

EXTENDED SERVICE PROGRAM (ESP)

TRUCK, CARGO, 2-1/2-TON, 6X6, M44A3 SERIES TRUCKS (DIESEL)

M35A3, W/O WINCH (NSN 2320-01-383-2047); W/WINCH (NSN 2320-01-383-3850);

M35A3C, W/O WINCH (NSN 2320-01-383-2050); W/WINCH (NSN 2320-01-383-2049);

M36A3, W/O WINCH (NSN 2320-01-383-2048); W/WINCH (NSN 2320-01-383-2046).

Section II. THEORY OF OPERATION

GENERAL

This section explains how components of the ESP vehicles work. A functional description of these

components and their related parts will be covered in the following paragraphs.

ENGINE SYSTEM OPERATION

The Caterpillar 3116 engine has a 403 cu in.(6.6 L) displacement, with 4.13 in. (105 mm) bore and

5.0 in. (127 mm) stroke. The engine is a four-stroke cycle, in-line 6-cylinder with direct fuel injection. The

engine is turbocharged with an Air-to-Air Aftercooler (ATAAC) system, and is rated 170 hp at 2700 RPM.

The engine lubricating oil, which is both cooled and filtered, is supplied by a gear-type pump. Bypass

valves provide unrestricted flow of lubrication oil to the engine parts when oil viscosity is high, or if either

the oil cooler or the oil filter elements should become clogged.

FUEL SYSTEM OPERATION

A mechanical governor, transfer pump, and high pressure unit injection fuel system provides 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 contaminants 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.

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 vehicle.

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 manually 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.