Fuel Gauge issues?

[CCA-Dave]

I have replaced the entire fuel system on my '63 Falcon. I put a new 16gal fuel tank into the car, and the matching sender. My fuel gauge works, and passes the factory manual tests of grounding the sender wire/etc. The coolant temperature gauge also works (and seems to be reasonably accurate). So, here's my problem:

My fuel gauge shows full when the tank is full, and slowly moves to empty once I've use a whopping 5 or 6 gallons of fuel.

This past week I drained the tank, pulled the sensor, and confirmed that the Ohm readings across the entire range match the specs. The float is free to move around correctly. Hooked the sensor up to the car, and with my girlfriend watching the gauge we worked out the gauge does not begin to move until the float is roughly 2/3rd "up", and that's when we see just below empty. And at then the gauge sweeps to full as the sender does too.

So...what now? Replace the actual fuel gauge, vibrator, or both?

[Luva65wagon]

What's more important is how much up/down travel actually occurred from the float from when the gauge read E to F (when you did the test outside the tank.) Often, E should come before you are actual out of gas. 2 or 3 gallons. This distance travelled needs to be equal to the height of the tank (bottom of tank - plus an inch for reserve fuel). Basically, if the sweep (not physical movement, stop to stop, but from where it reads E to F on the gauge) is currently more than the tank height shorten the rod, if less than the tank height, lengthen the rod.

I just bent my rod to match full at about 2/3 full and it hit E when I was about 1/8. So it doesn't move for a while and then it does and when it reaches E I know I better start looking for gas, but not frantic-like.

[CCA-Dave]

I originally thought the same, that I'd be bending the rod to work. But the gauge doesn't register anything until the sender is almost 2/3rd through the travel. I can't imagine that I'd be able to bend the rod to show the fuel correctly on only the top 1/3 of the gauge sender travel. The float can move properly through the entire tank, and the sender shows the correct ohm readings. Unfortunately I have no way to send a specific Ohm level to the fuel gauge to test it.

[Falcongek]

Have you checked it the needle of the gauge hasn't slipped on the shaft. Mine has.
If it's reading something at all (about 20% of the time), I have a 1/2 full tank when it's overflowing. With the tank at 1/2 full it's reading empty and with the engine shut off the needle pegs way beyond the E mark.
(I've noticed the needle kinda jumping on the shaft at startup.

Good luck with the hunt!
Rinke