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TM 10-3930-664-24 Section III.  PRINCIPLES OF OPERATION Paragraph Title Page Number Number 1-15 General, Principles of Operation 1-23 1-16 Power Train Assembly 1-23 1-17 Hydraulic System 1-29 1-18 Braking System 1-30 1-19 Electrical System 1-30 1-15. GENERAL. The theory behind the operation of the forklift is described in the following paragraphs. Each system is dependent upon the other   for   efficient   operation   of   the   forklift.      The   information   contained   herein   will   assist   maintenance   personnel   in understanding how the forklift functions.  This knowledge will assist in isolating components which have failed. 1-16. POWERTRAIN ASSEMBLY. a. The powertrain assembly supplies the power required to move the forklift and operate the hydraulic system pump.  It converts the energy from burning fuel to rotary motion to drive both the transmission and hydraulic pump.  The powertrain assembly consists of the following components: Four-cylinder, diesel fueled, water cooled engine Six speed transmission (3 forward speeds, 3 reverse) Front and rear driveshafts Front and rear axles Speed range and direction selector Service brake and inching pedal Differential lock system Oil pressure gauge Coolant temperature gauge Transmission oil temperature gauge b. Engine Fuel System.  The function of the engine fuel system (Figure 1-6 and 1-7) is to inject clean, atomized fuel into engine cylinders at a precise time near the  end  of  the  compression  stroke  of  each  piston.    Components  of  the system contribute to the delivery of fuel to the cylinders. c. The engine is equipped with a cam-actuated lift transfer pump.  Fuel flow begins as the lift pump pulls fuel from the supply tank.  The pump supplies low-pressure fuel (21-35 kPa, (3-5 psi)) to the fuel filter head, through the fuel water filter/separator and fuel filter, and to the injection pump. d. The  injection  pump  builds  the  high  injection  pressure  required  for  combustion,  and  routes  fuel  through individual high-pressure fuel lines to each of the four fuel injectors.  When high-pressure fuel reaches an injector, pressure lifts an injector needle valve against spring tension to let fuel enter the combustion chamber. 1-24

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