ENGINE COMPONENTS - TM-9-2815-220-240081

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Fuel Filters, Fuel/Water Separator Filter (Continued)

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TM-9-2815-220-24 Maintenance Manual for AVDS-1790 2CA 2DA and 2DR Air-Cooled 12-Cylinder Diesel Engines

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Fuel Injection Pump Advance Assembly

TM 9-2815-220-24

THEORY OF OPERATION

0004 00

ENGINE COMPONENTS

Fuel Filters (Continued):

Fuel Injection Pump Filter - Also know as

Fuel

"Last Chance Filter" or "Watchdog Filter" is

Filter

a ten-micron filter built onto the side of the

fuel injection pump.

Fuel Injection Pump:

The injection pump has three main functions.

First, it must meter, or measure, the amount

of fuel delivered to each injector nozzle. A

small amount of fuel is needed for an idling

engine, while a larger amount is needed for

high engine speed.

Second, it must pressurize the fuel delivered to the injector nozzles. The pump must be

capable of producing pressure higher than the nozzle opening pressure (greater than 3300 psi).

Third, it must distribute the fuel to the correct cylinder at the proper time.

The injection pump is a single plunger, constant stroke, distributor type. Although it is called

a single plunger type, the pump actually has a plunger in each of its two hydraulic distributing

heads. Each head supplies fuel to one bank of six cylinders. The pump is mounted between

the two cylinder banks and between the two fan towers. A shaft coupled to the accessory drive

gearing drives it. A timing advance unit is built into the injection pump drive to automatically

advance the injection timing at high engine speeds. The injection pump camshaft, gears, and

governor are lubricated by oil supplied from the engine main lubrication system.

Fuel Injection Nozzles and Tubes:

The fuel injection nozzle is a device that sprays fuel as a fine mist into the cylinder at the

proper time allowing efficient combustion. The injector nozzle must inject the fuel into the

combustion chamber in a pattern that produces maximum power and economy.

Twelve fuel injector nozzles, one per cylinder, are used to inject fuel into the combustion

chambers.

Fuel injector tubes of equal length carry the fuel from the fuel injection pump to the nozzles.

Interconnecting fuel return lines provide a path for the return of excess fuel from the nozzles.

WP 0004 00-19