Fuel Injection Pumps

A typical fuel injection system is composed of the following components fuel tank, injection pump, mechanical or electronic governor, timing device, fuel supply pump, high-pressure fuel injection lines, and fuel injectors. The high-pressure fuel injection pump is the core of the fuel injection system. The in-line pump and distributor pump are the most common in fuel systems. 

This fuel distribution and injection process occurs four times per plunger revolution for a 4-cylinder engine and six times per revolution for a 6-cylinder engine. Distributor pumps are not typically utilized on 8-cylinder or larger diesel engines. 

The amount of fuel metered is adjusted and controlled by the engine governor. All parts of the distributor pump are contained in one housing. Distributor pumps are lubricated by fuel which fills the housing. 

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. 

Standard in-line fuel injection pumps are driven by a camshaft following the speed of the engine. For 2-cycle engines, the camshaft speed is identical to the crankshaft rpm. For 4-cycle engines, the camshaft speed is one-half of the crankshaft rpm. The in-line injection pump parts, such as the camshaft and tappets, are lubricated by the engine oil. 

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It is noteworthy, however, that traces of sulfur can have beneficial effects on the anti-wear resistance of fuel injection pumps. It is thus undesirable to reduce the sulfur content to extremely low values unless additives having lubricating qualities are added. Independently from total sulfur content, the presence of mercaptans that are particularly aggressive towards certain metal or synthetic parts is strictly controlled. The mercaptan content is thereby limited to 0.002% (20 ppm) maximum. The analysis is performed chemically in accordance to the NF M 07-022 or ASTM D 3227 procedures. 

Lacey P, Lestz S. 1991. Failure analysis of fuel injection pumps from generator sets fueled with Jet A-1. Southwest Research Int San Antonio, TX. Belvoir Fuels and Lubricants Research Facility. 

Distortion of Diesel Fuel Injection Pump Parts... 

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. 

Lubricity is a term used to describe the ability of a fluid to minimize friction between, and damage to, surfaces in relative motion under load. Fuel helps to lubricate and prevent wear of high-pressure fuel injection pump components, especially under boundary lubrication conditions. Boundary lubrication is defined as a condition whereby friction and wear between two surfaces in relative motion are determined by the properties of the surfaces and the bulk properties of the contacting fluid. The bulk viscosity of the fuel or oil is not a critical factor under boundary lubrication conditions. 

A fatty acid based corrosion inhibitor can form a tenacious film on the metal surfaces of a fuel injection pump. The tight tolerances in high-pressure injection pumps require very little fluid film for proper lubrication. 

At excessively low temperatures, highly viscous fuel may inadequately fill the pumping chamber of distributor-type fuel injection pumps. Poor fuel distribution and engine operation can result. 

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

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. 

Continuous Spray Pump Fuel injection pump which provides a constant rather than an intermittent spray normally for fuel injection in spark ignition engines. 

The application focus of honing can be seen in automotive engineering such as finishing cylinder bores, crankshaft bores, fuel injection pump housings, etc. Another field of application is hydraulics and pneumatics. 

In order to develop rehable products with a long lifespan, it is necessary to predict possible causes of future damage in the use phase during the early construction phases already. Over the whole product life cycle, mechatronic products (e.g. electronic coolant pumps, high pressure fuel injection pumps, alternators) exhibit highly complex damage causes due to the interactions between the different subcomponents. 

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

A positive shutoff should be added just beyond the day tank whenever the tank is above the level of the fuel-injection pump. If the day tank is mounted on a structure that is subject to vibration, a flexible connector should be added between the tank and the fuel piping. (Actually, flexible connections are recommended between an engine and any support system, whether it involves fnel, air, water, or oil.) The weight of both the tank and the fnel must be considered when designing and mounting the tank. 

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. 

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