ok im going nuts here !

[WOLFMANmike]

ok so here is the scenario i have grounded out everything i can the truck has great grounds but my damn gas gauge only works when it wants to lol by this i mean i bought a new sending unit put it in and it worked for like a week . now i sware some times its heat related but now you get in turn on the key into the on position and the needle stays on empty put gas in it dont change .. drive anyway say to like another city maybe 15 miles and shut it off .. hang with my friends at a car show a few hours go to leave and turn the key boom working gas gauge even floating while driving now working stop at the store on the way home and turn truck off ... come back in 10 mins start it up no gas gauge again ! im gonna rip my freaking hair out here guys lol what in the name of all that is holy could be doing this to me ? is it possible that the key ignition switch isent sending the signal to it ? ... all so here is somthing else when the needle is sitting on the E if you hit the dash hard then the needle will peg over to full even if not having a full tank turn off key still stuck on full hit dash again drops to E lol but the sending unit is new the gauge is new all wires have great grounds im lost help pleaase