how long for gas to get into tank?

I have a '50 Dodge truck with fuel filler on side of cab, factory pipe so maybe 2', with a 90 degree into a tanks unlimited 16 gallon tank.
The question/problem was it ran out of gas early after 111 miles, but can go to 160, but I dragged a few people so did have my foot in the tank a few times (and gas gauge has become intermittent).

Ran out of gas, at gas station pump kept shutting off, and I could see the fuel all the way up to the cap. BUT this was after 8 gallons in a 16 gallon tank?

so either it was not empty (but won't start until I fueled up), or could the gas take a long time to get into the tank (I don't think it is vented, can't remember)

or could my pick tube have shrunk? it was the tanks inc factory top mounted pickup tube??

I understand everything but the 8 gallons full into an empty 16??

May have a rust hole in pickup tube like a hole in a straw of a soda cup letting it suck air. Tank not venting and sucking a vacuum on it.

My first thoughts were the same a Sneaky's, that you have a hole in your pick-up tube inside the tank, about 2 or 3 inches up from the bottom. As long as the gas is above the hole you're doing fine, but as soon as the gas is below the hole you're sucking air and rolling quietly over to the side of the road.

thanks, I went out today and after 1 gallon it was full.
I was thinking maybe something got sucked onto the pickup tube and went I dumped in more gas it washed off, or I never thought of a hole in the pickup tube. guess I will run it down to make it lighter and then drop it.

thanks for the responses.