See Figures 1, 2 and 3
There is an inline fuel filter located between the fuel pump and the carburetor on most models. On the early 4-134, all 6-226 and 1966-70 6-232 engines, the fuel filter consists of a sediment bowl mounted on the fuel pump. On the 6-225 engines, the filter is in the carburetor, behind the inlet nut. The inline fuel filter should be cleaned or replaced every 15,000 miles. If the vehicle is driven in abnormally dirty conditions or if contaminated gasoline was put in the gas tank, the filter could become clogged before 15,000 miles. The fuel sediment bowl type filter need not be serviced unless there is evidence of foreign matter (e.g., water, dirt) visible in the bowl. If there is, remove and empty the bowl, wipe it dry with a clean cloth and replace it.
On the 6-173 and 225 engine, when replacing the filter, hold the large nut with a wrench and unscrew the fuel line fitting. Pull the fuel pipe from the carburetor and catch any fuel with a clean rag. Next, unscrew the large nut. There is a spring behind the nut, so be careful. Remove the spring and the old filter. Install the new filter and, if you are at all in doubt about its condition, a new gasket behind the inlet nut. Tighten the inlet nut carefully, because the carburetor is made of very soft metal and the threads could easily strip with disastrous results! Hold the inlet nut securely while tightening the fuel line fitting.