Diesel fuel injection pumps

Distortion of Diesel Fuel Injection Pump Parts... 

Leakage past diesel fuel injection pump plunger in worn equipment may occur can result in hot restart problems whereby fuel leaks past the injection plunger in hot equipment restarting may be impossible until the engine cools down. 

Inadequate Filling of Diesel Fuel Injection Fuel Pump... 

If a diesel fuel is low in viscosity due to kerosene dilution or solvent dilution, its lubricity is probably poor. The possibility of wear of the high-pressure fuel injection pump parts will increase. The effect of kerosene dilution on the lubricity of a typical low sulfur diesel fuel is shown in FIGURE 5-2. 

High-pressure diesel fuel injection systems contain expensive and sophisticated components. The high-pressure pump and injector are the key components to ensuring proper fuel management within the diesel engine. Clearances and tolerances between moving parts of the fuel pump are quite fine. Even a small amount of deposit, contamination, or corrosion can significantly alter the efficient performance of the fuel injection system. 

Shearing of high-viscosity diesel fuel by the fuel injection pump can result in excessive heat buildup and distortion of the pump components. 

Tschoke, H. 1994. Distributor injection pumps VE. In Diesel Fuel Injection, ed. Ulrich Adler, Horst Bauer, and Anton Beer., pp. 148-161. Robert Bosch GmbH Stuttgart. 

Auxiliary engine parts of the diesel engine fuel injection pump with fuel line, cooling water pump, lubricating oil pump, turbocharger... 

Figure 5.3 shows a typical fuel circuit for a diesel engine with its fuel injection pump and a filter-water separator, such as is shown in Figure 5.4. 

For a long time the official specifications for diesel fuel set only a mciximum viscosity of 9.5 mm /s at 20°C. Henceforth, a range of 2.5 mm /s minimum to 4.5 mm /s maximum has been set no longer for 20°C but at 40°C which seems to be more representative of injection pump operation. Except for special cases such as very low temperature very fluid diesel fuel and very heavy products, meeting the viscosity standards is not a major problem in refining. 

Viscosity. For optimum performance of diesel engine injector pumps, the fuel should have the proper viscosity. Too low viscosity results in excessive injector wear and leakage. Viscosity that is too high may cause poor atomisation of the fuel upon injection into the cylinders. 

Diesel fuel prevents wear of high-pressure fuel pumping and injection equipment parts. If the viscosity of diesel fuel is low, its ability to form a hydrodynamic lubricating film between moving metal parts diminishes. The term lubricity is used to describe the wear-inhibiting capability of distillate fuels. 

In recent years, the concern over fuel lubricity has led to the use of a high concentration of corrosion inhibitors to improve diesel fuel lubricity performance. The film formed on the metal surface by fatty acid type corrosion inhibitors improves fuel lubricity. However, the result of this overtreatment may lead to sticking of injection pump parts. 

High-pressure diesel fuel pumps are not tolerant of dirt, debris, and organic deposits and can be seriously damaged by fuel contaminants. The barrel and plunger clearance is within a 1 to 2 micron tolerance. This tolerance is necessary to ensure that fuel injection pressures are maintained with minimal leakage past the plunger shaft. For this reason, thorough and complete filtration of fuel is required before the fuel reaches the injection pump. 

Fuel, usually gasoline or diesel fuel, is transferred to the engine from the fuel tank (or tanks) by this pump, which is either a mechanically driven device or, as is now more common, electrically driven. The fuel pump delivers fuel to a carburetor (gasoline) or fuel injection system (diesel and newer gasoline engines), which distribute the fuel under pressure in a spray to the proper cylinder. Many devices that were formerly mechanically driven are now replaced by computer-controlled devices. 

Lacey, P. I., and Lestz, S. J. 1992a. Effect of Low-Lubricity Fuels on Diesel Injection Pumps—Part I Field Performance. SAE Techn. Paper Ser. Warrendale PA Society of Automotive Engineers (Paper No. 920823). 

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