Figure 1-29.—Diesel fuel system.mixture in the cylinders for the harder job of starting atlow temperature.DIESEL FUEL SYSTEMThe primary job of the diesel fuel system is to injecta precise amount of atomized and pressurized fuel intoeach engine cylinder at the precise time. The major partsof the diesel system are the fuel tank, fuel transfer pump,fuel filters, injection pump, and injection nozzles(fig. 1-29).Fuel Transfer PumpThe fuel transfer pump is normally used on modernhigh-speed diesel engines. It can be driven by eitherengine or battery voltage. The fuel transfer pump can belocated on the outside of the fuel tank in the supply line,submerged within the fuel tank, or mounted on thebackside of the injection pump. The fuel pump pushesor draws the fuel through the filters where the fuel iscleaned.Injection PumpSeveral types of injection pumps are used on dieselengines. Each has its own unique operating principles.The primary function of the injection pump is to supplyhigh-pressure fuel for injection.Injection NozzlesA wide variety of injector nozzles are in use today.All are designed to perform the same basic functionwhich is to spray the fuel in atomized form into thecombustion chamber of each cylinder.Cold Weather Starting AidsDiesel fuel evaporates much slower than gasolineand requires more heat to cause combustion in thecylinders of the engine. For this reason, preheater andstarting aids, called glow plugs, are installed onequipment equipped with diesel engines.PREHEATERS.— Preheaters are normallyinstalled in the intake manifold; however, in atwo-stroke cycle engine, they are placed in the airpassages surrounding the cylinders. The preheater burnsa small quantity of diesel fuel in the air before the air isdrawn into the cylinders. This burning process isaccomplished by the use of either a glow plug or anignition coil that produces a spark to ignite a fine sprayof diesel fuel. The resulting heat warms the remainingair before it is drawn into the cylinders.1-21
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