A couple of months ago I bought an 1984 F350 crew cab 4x4 truck. This truck has the 460 in it. The problems I am having is that it takes about 20min to feel each tank. I can't just put the nozzle in and fill. I have to hold the nozzle so I can see the gas and fill slowly. Other wise it gets backed up and come out. Any one have any Ideas. I Also have a problem with the fuel gage. If I fill the front tank up all the way the full gage moves to show that it is full but as you drive it goes down rather slowly but does not show an accurate reading and it only moves when the tank is full. I do not get any reading with with the back tank. Does any one have any ideas. Thank you for your help.
When I swapped my '83 bed to a newer '95 bed a few years ago, I had to wrestle with the filler tube to get around a similar problem. In my case, the inner tube that allows the air to flow out as you're filling the tank was not getting proper flow.
With the problems you're seeing with the level readings, could be that someone got into the tank to do some work and didn't reconnect everything properly.
I was able to get my air line un-kinked without completely removing the tank but then again, I wasn't having trouble with my readings so I didn't have to go further. I just made sure fuel could flow down and air up smoothly and at the same time.
Check the tank vent hose. Make sure someone didn't drop something down the filler neck. Like kids flush toys down the toilet some times. They get stuck in the toilet drain & pretty soon the toilet is flushing slower & slower.
As for the fuel gauge if the wires to the sender are tight it is most likely the float in the tank I believe that is a single unit sender & fuel pump. REPLACE.
I owned an 86 F250 4x4 & have dealt with the issue before.
So I pulled the bed off and found that the filler hoses were cracked by the tank and leaking so I replaced those hoping to fix the problem but still have the filling problem. I took it camping this last weekend and hauled a 10 1/2 foot cab over camper. Got about 20 miles out side of town and started running a little rough. pulled over and found that back tank was boiling and tons of pressure while I was running off the front tank. So I switched to the back tank and it ran fine. Coming home It ran fine until I got on the free way. Then it started backfiring like crazy if I ran the engine over 40 miles an hours. So pulled over and had gas coming out of the filler spout with the gas cap on. limped it the rest of the 15 miles home. It acts like it is not getting enough fuel now when I start it. I have to push on the gas to a little to keep it idling right. It will idle but it is rough. I should let you know that when I took the bed off I found that my tanks have a single fuel line going into the sending unit, but I have two lines that run to each tank and one goes to the sending unit and the other is plugged with a bolt on both tanks. Also right in front of the front tank there is a fuel filter and in front of that there is an aftermarket inline fuel pump. I am so lost any help would be appreciated.