CARBURETOR The carburetor used on all Ford Tractor engines from the 1955 through the 1960 are basically the same type, with the same operating principles. The size of the main jets, however, vary depending on the size of the engine. The carburetors are the plain tube, up draft type. Interchange of carburetors on the manifold is impossible, as the carburetor stud spacing is different for each size carburetor.
tion, the float assembly positions so that the inward flow and the outward flow are about even. The float system is a dual float mechanism, used in a float chamber or fuel bowl that almost completely surrounds the main discharge nozzle. This construction permits operation of the engine at any angle up to 45 0 • 2. The idle fuel system, shown in Figure 3, controls the flow of fuel at idle speed and at slow speeds until the throttle is opened wide enough to allow the power system to operate.
A. Operation To understand the operation of a carburetor it i~ necessary to bear one basic fact in mind. The only function of a carburetor is to mix air and fuel and supply that mixture to the engine in the proper amount, and at the proper time. The Ford tractor carburetor is made up of four systems, see Figures 2 through S. These systems are: the float system, the idle system, the power fuel system, and the choke system. Each system except the float system supplies a fuel air mixture to the engine under different conditions of engine demand. Therefore, with all the systems functioning properly, the carburetor supplies the correct fuel air mixture through the entire range of engine operation.
When the throttle plate (6), is in the idle position, it is slightly open, with the edge of the plate between the primary and secondary idle orifices (7) and (8). With the plate in this position, the air pressure at the primary orifice is lower than the air pressure in the fuel bowl chamber, due to manifold vacuum at the primary orifice. Therefore, fuel is forced from the fuel bowl into the idle passage (10), Figure 3. As the fuel travels through the idle fuel passage, it passes through the idle jet (11), to the point where it is combined with air entering through the idle fuel adjustment needle seat (12) . The fuel is mixed with air again when it passes the secondary idle orifice as it travels through the idle fuel passage. The mixture that emerges from the primary idle orifice is rich, however, it is reduced to the correct proportion by the air passing the throttle plate.
1. The float system, as shown in Figure 2, controls the level of the gasoline in the carburetor fuel bowl, and admits fuel as necessary to maintain the proper fuel level throughout the operating range of the engine. As the fuel level lowers, the float lowers and the float valve (3), Figure 2, opens to admit more fuel to the float bowl. As the fuel reaches the operating level, the float raises, dosing the float valve, which shuts off the fuel supply. Actually, during normal opera-
flOAT VALVE
Figure 2- Floot System
Figure 3- lole Fuel System
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