Automotive Systems

Formerly Automotive Systems I

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Fuel Pump

Fuel Pump

The PSB model fuel pump is similar to other distributor fuel system, in that a pump sends a measured amount of fuel to each injector at a properly timed interval. The difference in the PSB system is that the amount of fuel sent directly from the pump at high enough pressure needed for injection. This eliminates the need for unit-type injectors and the associated linkage and camshaft, making the system less cumbersome.

The purpose of the fuel pump (fig. 5-31) is to deliver measured quantities of fuel accurately under high pressure to the spray nozzle for injection. The positive displacement fuel supply pump (fig. 5-32) is gear-driven by the pump camshaft through an engine camshaft gear and provides fuel to the hydraulic head for injection and cooling.

Figure 5-33 shows fuel intake at the hydraulic head. Injection (fig. 5-34) begins when fuel flows around the fuel plunger annulus (fig. 5-35) through the open distributing slot to the injection nozzle. A continued upward movement of the fuel plunger causes the spill passage to pass through the plunger sleeve (fig. 5-36). This reduces pressure, allowing the fuel delivery valve to close, ending injection. This is accomplished through a single plunger, multi-outlet hydraulic head assembly (fig. 5-31).

The plunger is designed to operate at crankshaft speed on four-cycle engines. It is actuated by a camshaft and tappet arrangement. The pump camshaft, which also includes the gearing for fuel distribution, is supported on the governor end by a bushing-type bearing and by a ball roller bearing on the driven end. An integral mechanical centrifugal governor (fig. 5-37), that is driven directly from the pump camshaft without gearing, controls fuel delivery in relation to engine speed. This pump has a smoke limit cam within the governor housing to assist in controlling exhaust smoke of various fuels. The mechanical centrifugal advance unit of this pump provides up to g-degrees advance timing and is driven clockwise at crankshaft speed.

Figure 5-31.—Metering and distributing fuel pump assembly-left sectional view.

Figure 5-32.—Fuel supply pump assembly—sectional view.

Figure 5-33.—Fuel intake flow diagram.

Figure 5-34.—Beginning of fuel delivery flow diagram.

Figure 5-35.—Fuel delivery flow diagram.

Figure 5-36.—End of fuel delivery flow diagram.

Figure 5-37.—Governor—sectional view.

Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

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