Okay- this is wierd... Got home yesterday with half a tank... Got in the truck a few mins ago.... Started it up and I am barely above E. so at first I thought leak.... Nope..... No fuel anywhere.... Next I thought maybe someone siphoned my fuel since i don't have a. Locking cap.... Drove to the store..
Got back in the truck, started it up, I'm back at half tank again.... Anyone ever seen this?

 

yea ive seen it happen to mine twice, Once when i left the power on, on the truck(not started, just left the power on.) It took it around 30 minutes for it to finally adjust.

the next time it happened was when i filled my tank about halfway. Then one morning my tank was at full, I was confused and didnt know what was going on. First thing i thought was maybe someone tampered with my fuel and added something to it, but the truck was running fine and I look at the fuel door and cap and it doesnt seem to be tampered with. Later on it just adjusted on its own after a 30 minute drive( the fastest ive seen it drop to half a tank)

But yea ive seen it happen to my truck, except it didnt go to E it went to F.

 

Yea mine does it all time. Goes from like a quarter to pretty much nothing. One night I was jumping my aunts van and left the truck running for about 5 mins it had a quarter of a tank and then I got back in and my low light was on.

 

If I park my truck on a slight incline my fuel gauge goes up and if it gets parked facing downhill it goes down. I'm used to it since I live in the mountains. And it always happens when the key is on!!!

 

It's the fuel sensor. All it is is a glorified float valve, and with age (or improper replacement) start to bounce a bit more freely. Mine wasn't installed quite right, but through consistent fill-it-til-you-see-it, it kinda fixed itself, though now it bounces crazily while trail-riding.