I've got a couple of issues with the tank and gauge in my '57 F100.

1. When the gauge reads near empty the truck only takes 7-8 gallons of gas. I pulled the sending unit out (to replace the gasket) and it appears to be in great shape. I also check the voltage to the wire that connects to the sending unit at it varies between 5-7 volts. Not sure if that is right. Does anyone know what the correct read at that point should be? Any suggestions on how to fix this or is this an inherent problem with these trucks? I'm wondering if running a new wire might help?

2. When I do fill up the cab wreaks of gas. I noticed when I bought the truck that there was a lot of gas residue around the sending unit so I replaced the gasket. Now I want to replace the hose between the filler pipe and the tank. Does anyone know what the ID of that is? I am thinking I can get some rubber hose from a local auto parts.

Thanks!

 

The shop manual states the voltage should oscillate between zero and about 10V if it does not there is fault with the instrument gauge regulator or there is short to ground between the regulator and the gauges. Of course this would be measured with an analog meter.

I would suggest picking up the shop manual for you truck it will make your life a whole pile easier

As for the hose just measure it.....

 

You can hook up the + wire and use a jumper for ground to sweep the sender through it's range of motion with it out of the tank. Sometimes the arm needs bent. Usually if there is voltage at the wire, it is a problem in the sender. It can be checked with an ohm meter but I can't tell you the range or what it would be at full, half, empty ect. but that information should be out there.
I don't know if parts store hose is going to be good for gasoline but I ordered mine from Dennis Carpenter and got the cab grommet, proper gas cap, float and sender gasket all. Worth it.

 

If your area uses gasoline with alcohol get fuel injection hose. The alcohol will degrade regular gas hose.