McIntosh & Seymour Diesel Full first Diesels manufactured by the McIntosh & Seymour Corporation were equipped with fuel pumps somewhat after the design appearing in Fig. 136. The engines were four-cylinder units, and the fuel pumps had two pumping plungers, one plunger for each pair of cylinders. The fuel from one plunger cavity passed through the discharge valve and pipe line into a block, called the Dis tributor. This block contains two passages connected to the fuel lines leading to the two fuel injection valves. The cross sections of these passages are controlled by needle valves. The fuel, entering the distributor, divides into two streams; the needle valves allow the operator to properly proportion the two oil streams.
The operating difficulty of this pumping system lies in the inability of the engineer to regulate the distribution of the fuel on varying loads. A setting of the needles that is correct for full load will not give the proper regulation at low loads since the resistances of the passages vary, due to a smaller quantity of oil entering the distributor. Another factor that prevents proper proportioning of the fuel is the partial clogging of one line; this throws almost all the oil into one cylinder.
With this form of pumping mechanism it is imperative that the oil is filtered to prevent the clogging of a distributor. Further more, the fuel valves must be kept in perfect condition since the smallest leak in a fuel injection valve lowers the resistance of this particular fuel line, allowing this cylinder to receive too large a proportion of the fuel from the pump.
The fuel pump, mentioned above, gave way to a design which is shown in Figs. 137 and 138. Unlike the distributor type pump which followed Sulzer Bros. patents, Fig. 137 is of exclu sive American design. This pumping apparatus consists of two pumps, set at right angles, each being an outside packed double-plunger pump. The eccentric strap E driving the two plungers is mounted on an eccentric D, and the governor acts directly on the pump plungers, in this way regulating the amount of fuel pumped by varying the plunger stroke. The reaction on the governor of direct plunger controlled pumps is considerable. McIntosh & Seymour partially avoid this by using two eccentrics; the eccentric D, controlled by the governor, drives the pump and is mounted on a second eccentric B that is keyed to the vertical governor shaft C. It is apparent that this
offers a more accurate regulation of the pump stroke and a greater reduction in the reaction on the governor than can be secured by a single eccentric.
The pump suction valves are located below the discharge valves, being removed through the discharge valve opening. The latter valves are accessible by the removal of the valve cap or plug G. Below the suction valves of the two pumps is placed a shaft H, which has two milled cams, as shown in the cross section, During the functioning of the pump the suction valve stems clear the shaft by means of the depressions in the shaft. Rotation of the shaft lifts the suction valve, thereby filling the pump with oil.
Pump continued regrindings of the suction valve, the stem touches the cam at its lowest position. This cocks open the valve, preventing any fuel reaching the injection valve. Grinding the end of the stem will allow it to clear the cam. This same trouble frequently occurs in regrinding the dis charge valve, causing it to strike the suction valve. The clear ance between the two should be approximately inch.
The valve springs at times break. This is probably due to fatigue; replacement by a spring of smaller wire in most cases seems to remedy this trouble. The discharge valve should be allowed a lift of at least .025 inch. The valves have a 60-degree slope. In regrinding more care is necessary than with a 45 degree valve seat.
The discharge valve cap is sealed with a metallic gasket. This gasket must be absolutely clean to avoid leaks. Leaks around the valve cap are quite prevalent with many makes of pumps; not only is the dripping oil unsightly but it also impairs the engine regulation.
The plunger stuffing-box glands are best packed with shredded lead or vulcanbestos. Watch engineers should be cau tioned not to tighten up on the glands with too great a pressure. This binds the pump plunger, scoring it and increasing the gover nor reactions.
Fuel Pump fuel pump and eccentrics come from the factory properly timed, and no change is necessary. In case it appears that the eccentric has slipped, the best method of checking the setting is to place the engine with the piston of No. 1 cylinder on bottom dead-center, just starting the compres sion stroke; in this position the pump plunger should be at the end of its delivery stroke.