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Figure  1-26.Venturi  effect.
Air Induction Systems

Equipment Operator Basic - Beginning construction equipment operators manual
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Figure  1-29.—Diesel  fuel  system. mixture in the cylinders for the harder job of starting at low  temperature. DIESEL FUEL SYSTEM The primary job of the diesel fuel system is to inject a precise amount of atomized and pressurized fuel into each engine cylinder at the precise time. The major parts of the diesel system are the fuel tank, fuel transfer pump, fuel  filters,  injection  pump,  and  injection  nozzles (fig.  1-29). Fuel Transfer Pump The fuel transfer pump is normally used on modern high-speed diesel engines. It can be driven by either engine or battery voltage. The fuel transfer pump can be located on the outside of the fuel tank in the supply line, submerged within the fuel tank, or mounted on the backside of the injection pump. The fuel pump pushes or draws the fuel through the filters where the fuel is cleaned. Injection Pump Several types of injection pumps are used on diesel engines. Each has its own unique operating principles. The primary function of the injection pump is to supply high-pressure fuel for injection. Injection Nozzles A wide variety of injector nozzles are in use today. All are designed to perform the same basic function which is to spray the fuel in atomized form into the combustion chamber of each cylinder. Cold Weather Starting Aids Diesel  fuel  evaporates  much  slower  than  gasoline and requires more heat to cause combustion in the cylinders of the engine. For this reason, preheater and starting  aids,  called  glow  plugs,  are  installed  on equipment  equipped  with  diesel  engines. PREHEATERS.—   Preheaters   are   normally installed   in   the   intake   manifold;   however,   in   a two-stroke  cycle  engine,  they  are  placed  in  the  air passages surrounding the cylinders. The preheater burns a small quantity of diesel fuel in the air before the air is drawn  into  the  cylinders.  This  burning  process  is accomplished by the use of either a glow plug or an ignition coil that produces a spark to ignite a fine spray of diesel fuel. The resulting heat warms the remaining air before it is drawn into the cylinders. 1-21







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