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M88A1 APUM88A1 APU

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Location:

Right/RearSide Of

Vehicle

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APU

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The fuel system filters and delivers fuel

to the engine Cylinders at the correcttime for ignition. The system consists of

a primary fuel filter, secondary fuel filter,

injection pump and fuel injection

nozzles. ( DJBMA has a fuel transfer

pump and sediment bowl )

Fuel System

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Primary and

Secondary Fuel

Filters

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Emergency

Fuel Shutoff

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Injection pump The injection pump is a constant stroke,plunger-type pump. The pump is driven by the camshaft

and it delivers an accurate amount of fuel under high

pressure to the injection nozzles.

Injection nozzles The injection nozzles open at apressure of about 1750 psi. and deliver fuel in a fine spray

to the pre combustion chamber at the correct time for

ignition.

Fuel return Excess fuel is returned to the fuel tank aftereach injection cycle attached to each injection nozzle.

A bleed valve on the return line allows excess fuel to

Combine with flow-through fuel from the injection pump.

Fuel System Components

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Fuel transfer pump ( DJBMA ) The fuel transfer

Pump operates off the engine camshaft. Fuel is pumpedFrom the vehicle right side fuel tank (M88A1 only) through

The primary and secondary fuel filters to the fuel

injection pump.

Fuel System Components

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Injector nozzleInjector nozzl

PreheaterGlow plug

Fuel return

Sediment bowl

Fuel transfer

pumpInjector pump

Fuel Component Location

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Preheat Relay & Fuel Shutoff

Preheat Relay Fuel Shutoff

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Pressure lubrication is provided to all working parts

of the engine. The lubrication sys. Includes a gear-type

oil pump assembly with oil intake cup, a bypass valve,

an oil cooler and oil filter mounted on the oil filter adapter

assembly. Oil lines and passages distribute oil to theworking parts of the engine. A crankcase breather is

used to aid oil consumption control. The stand-pipe

breather, located under the rocker arm cover, vents

crankcase fumes from the rocker arm cover to the

cylinder head intake port.

APU Lubrication System

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Oil pump assembly The oil pump is mountedOn the gear case back plate and is driven by the

crankshaft gear. The pump draws oil from the

crankcase, through the screened oil intake tube, to the

oil filter.

Oil filter The oil filter element is mounted on the oilfilter adapter. Oil drawn from the crankcase by the oil,

pump is forced through the oil filter to the rocker arm

cover, the crankshaft and camshaft bearings, andthe connecting rod bearings. Oil then flows through the

connecting rod passages to the piston pin bushings.

Lubrication Components

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Oil cooler The oil cooler is mounted is mounted onthe oil cooler plate and is located above the flywheel.

Hoses connect the oil cooler to the oil filter adapter.

Bypass valve assemblyThe oil bypass valve is

located on the rear bearing plate and is used to control

oil pressure. The valve is normally closed. When oil

pressure reaches about 25 psi the valve opens, allowing

excess oil to flow directly back to the crankcase.

Oil pressure switch The normally open contactsof the oil pressure switch close at 14 + 2 psi decreasing

pressure. The contacts open at 14 + 2 psi increasing

pressure.

Lubrication Components

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A. Oil Pump Assembly

B. Oil Intake cup

C. Bypass valve

D. Oil Cooler

E. Oil Filter

F. Crankcase Breather

G. Standpipe Breather

H. Rocker Arm Cover

Component Locations

E

F

G H

D

C

A

B

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i. Oil Drain Valve

j. Drain Handle

Component Location Cont.

i

j

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A 300-ampere, 28 + 7 volt generator functions as a

starter motor. When the preheat switch is actuated, 24

volts direct current (vdc) is applied to the generator

field coil from the preheat relay. When the start switchis actuated 24 vdc is applied to the generator armature

from the starting relay. This motorizes the generator.

The generator is coupled to the engine by a drive chain.

When the engine starts, the current in the armature

reverses direction, and the motorized generatorresumes normal generator operation.

Generator

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Starter/Generator

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Chain Case & Drive

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Starter Relay

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The auxiliary system of the vehicle has the

following functions: to supply power for control

and emergency operation of the boom; to supply

power for control and emergency operation of

the spade and winches; and to supply power foroperation of refuel pump and impact wrench.

Auxiliary Hydraulic System

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Hydraulic Pump

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The constant speed governor maintains engine speed at 2000 + 100 rpmduring changes in power demands, by automatically varying the throttle

position. Adjusting the engine speed a hand held stroboscope must be

used. ( TM 9-2350-256-34-1 Pg. 4-20.3 )

Governor Adjustment

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B. Injection pump

C. Control lever

D. Linkage & arm

E. Shaft

F. Yoke

G. Cam gear

H. Cup

I. Fly balls

A. Speed adjustment nut

13

J. Sensitivity adjustment nut

A

B

D

E

I H

G

F

JC

Governor System

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Power Train

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Fuel Transfer Controls

FOUR-WAYSELECTOR VALVE FLOWREGULATOR

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PUMP

MOTOR

Refuel Pump and Motor

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APU Control Box

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APU Schematics