Fuel Filters

Fuel filters stop contaminants (rust, water, corrosion, and dirt) from entering the carburetor, throttle body, injectors, injections pumps, and any other parts that may be damaged by foreign matter. Fuel filters can be located in the following locations (fig. 4-6):

• A fuel strainer is also located in the fuel tank on the end of the pickup tube.
• In the fuel line right after the electric fuel pump.
• Under the fuel line fitting in the carburetor.
• Inside the fuel pump.
• In the fuel line before the carburetor or fuel injectors.

When in doubt about the location of the fuel filter, refer to the service manual.

Fuel filters operate by passing the fuel through a porous filtering medium (fig. 4-7). The openings in the porous material are very small, and, therefore, any particles in the fuel that are large enough to cause problems are blocked. In addition to the filtering medium, the filter, in some cases, also serves as a sediment bowl. The fuel, as it passes through the filter, spends enough time in the sediment bowl to allow large particles and water to settle out of it.

Several types of fuel filters are used today. They are the replaceable in-line, the replaceable in-line in the carburetor, and the glass bowl (fig. 4-8). The most common configuration is the replaceable in-line filter. these are in-line filter elements that fit in the carburetor inlet or inside the fuel tank. Fuel filter elements can be made from treated paper, ceramics, sintered bronze, or metal screen (fig. 4-9). However, there is one filter element that differs from the others. It consists of a stacked pile of laminated disks that are spaced 0.0003 inches apart. As the fuel passes between the disks, foreign matter is blocked out. These filters are replaced when the flow of fuel is restricted.

Fuel filter service involves periodic replacement or cleaning of system filters. It may also include locating clogged fuel filters that are upsetting fuel system operations. Paper elements must be replaced when clogged or after prolonged use. Sintered bronze fuel filters can usually be cleaned and reinstalled. A clogged fuel filter can restrict the flow of fuel to the carburetor or injectors. Engine Performance problems will show up at higher speeds.

Some fuel filters have a check valve that opens when the filter becomes clogged. This will allow fuel contaminants to flow into the system. When contaminants are found in the filters and system, the tank, the pump, and the lines should be flushed with clean fuel.

Always refer to the service manual for information concerning service intervals, cleaning, and replacement of all system filters.

Figure 4-6.—Typical fuel filter locations.

Figure 4-7.—Fuel filter operation.

Figure 4-8.—Fuel filter configurations.

Figure 4-9.—Fuel filter elements.