when the fuel sloshes it could suck air. The jury is still out if my gauge reads way past the F mark. I'm sure it will.
Everybody goes into a big panic about an indirect injection engine sucking air into the draw line; these engines are and always have been self-bleeding, providing there is fuel to pick up.
I have watched people swap fuel filters and then go through a big ordeal "bleeding" = absolutely hogwash and no need whatsoever.
If you have enough battery, an engine that has ran dry of fuel will pull up the fuel, fire off, and run with no bleeding whatsoever.
Back when we all had 6.9 diesels long-hauling cattle (and now with the direct injection 6BTs), we would run a tank until the engine stumbled and ran out of fuel; switch the manual fuel valve to another tank, and the engine would pick it up and be running strong within half-a-mile at road speed.
When a gauge reads way past full, the float is as far up as it will go and submerged.
The float rod needs bent, or lengthened or shortened, such that when the float is against the top of the tank, the needle is on the F, not way past the F.
There are two variables governing level and duration of the gauge; rod configuration and "Sweep"
Sweep is achieved by lengthening the float arm.
E being E and F being F are governed by the height of the pivot point; you want the pivot point exactly in the center of the tank's capacity.
Get the pivot point above center and the needle will be on E a long time before the tank is Empty.
Get the pivot point below the center and it will show F a long time.
Before bending anything or lengthening/shortening anything, you want to find exactly the center of fuel depth with a full tank and raise or lower your pivot point to match that.
Then, you want the rod long enough that the float doesn't stop in it's travel until it is either touching the bottom of the tank or against the top of the tank.
With a tank that has clean lines, not all deformed, set your pivot point at exact center and lengthen the arm until the float can touch top and bottom; then, make any fine adjustments from there.
It helps if the tank is bone dry.