Determining a stuck fuel sender from outside the truck

[ml68nova]

A quick question and maybe a stupid one as well,

I have a 72 c30 dually wrecker and my gauge is staying a 1/4 tank but moves at 1/16 either way when using or filling the tank. It just happend last week while towing my car.

I supect the float is stuck or heavy (has a crack) But I would like to check it before taking out the seat (solid will not fold) and yada yada.

Has anyone used a rod through the filler neck to move the float? I noticed from pictures ,the sender is located more to the passenger side possablly making this idea a mute point.

Thanks,Mark