kyusik

i have an 87 f350 with a rear tank from an 87 f150. the sending unit wont work in the tank, but if i take it out it works. i hooked up some extra wire so i could watch the gauge and put the sending unit in a bucket of water and it worked there. its not hanging up in the tank. i pulled the breather out of the top of tank held a flashlight up there and looked down the fill tube, poked at it with some wire. the float does what its suppose to. there is about a 1/4 tank in there now. has anybody had this problem any help would be great. thanks