I have a manual pointed metal fuel switch on the floorboard between the drivers seat and the drivers door. When I switch it to the front tank behind my seat there is no reading on my fuel gauge. When I select the rear tank the fuel gauge only goes to 3/4 when it is full. I do not know what to do, what are my steps to determine what is wrong and fix it.

 

1967/72 F100/350 with optional 25 gallon auxiliary fuel tank has a manual control fuel tank selector valve located on the drivers side of the floor adjacent to the seat.

The selector switch located under the dash to the left of the steering column only changes the dash fuel gauge from one tank to the other.

So, not only do you have to change the valve, but also operate the switch to change the reading of the dash fuel gauge from one tank to the other.

 

Thank you so much! I did not know there was a switch under the dash,,,,,do you know how many years I have had this? My dad bought it new then when he passed in 1983 it was given to me,,,,,,never knew how it worked,,,dad never told me,,,,,been guessing with the front tank behind the seat,,,,,,and dealing with a sending unit that I changed when I restored the truck,,,,,i did not know how to fix the fact that it only reads 3/4 when the tank is full,,,,if you know how I can do that or if you can direct me to a place like tube where I could see how to fix it I would sure appreciate it,,,,. Thank you again.

 

Selector switch shown as 9A050 in pic.

The usual reason why the dash fuel gauge doesn't read correctly:

The fuel sending unit float is made from two pieces of brass soldered together. Solder breaks down, gas seeps in, float settles towards the bottom of the tank.

Both the in-cab and 25 gallon auxiliary fuel tank sending units use the same float (C0AZ-9202-B). It's available from Ford and the repop parts sellers.

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