Description of Fuel Supply System Plumbing

FIGURE 6:

FIGURE 7:

FIGURE 8:

FIGURE 9:

FIGURE 10:

FIGURE 11:

The fuel system is shown in schematic form in Figures 6 and 7. The fuel system utilizes an in-tank electric fuel pump or pumps (Figure 8). Fuel is delivered to a vapor separator (Figure 9) just forward of the carburetor through a series of metal and composition lines (Figures 10 and 11). Fuel passes through the vapor separator by unseating a spring loaded valve and proceeds to the carburetor inlet fitting.. A portion of the fuel entering the vapor separator passes through an orifice and into a metal line which returns fuel to the fuel tank or tanks.
If the fuel in the supply line gets hot enough to form vapor bubbles (boil), the bubbles are vented into the vapor return line to prevent vapor lock.

FIGURE 8:

Filteration of the fuel is accomplished at three points:

^ Fuel pump inlet filter (Figure 8).

FIGURE 9:

^ Screen at inlet of vapor separator (Figure 9).

FIGURE 12:

^ Sintered bronze carburetor inlet filter (part of carburetor) (Figure 12).

FIGURE 10:

FIGURE 11:

Fuel tank combinations provided by Ford Motor Company are shown in Figures 10 and 11. The DSO (Domestic Special Option) forty gallon capacity single fuel tank became available during the first quarter of 1984 in limited quantities. An in-line fuel filter, with a replaceable element, mounted on the left frame rail was released as a running change on the forty gallon system during the third quarter of 1984.
Prior to the release of the single forty gallon capacity fuel tank as a DSO option, various manufacturers of motor homes provided fuel tanks and fuel pumps of their own design. These systems utilize the original Ford plumbing to and from the fuel tank. In some instances, the Ford in-tank electric fuel pump is adapted to the fuel tank. In others, a fuel pump from Holley or Carter is used. In at least one manufacturer's system the Ford in-tank pump is used in series with a Carter pump mounted just downstream of the fuel tank.
In-line fuel filters are used in some of the non-Ford fuel tank systems. In most cases the filter is of a type that the filter element can be replaced as a maintenance item.