I have a 96 blazer and we replace the fuel pump in it not to long ago. Ever since and before it was replace it bounces and does it's own thing. On a full tank it sits past the F. When you go to drive it it bounces with the truck and I'm not sure if float is stuck on barrier in tank of if it's something electrical. Also it is on empty at Half a tank. Anybody know what could cause this?

 

Your fuel level sensor is more than likely messed up, it's part of the unit with the fuel pump. Mine is sort of the same, at full (when the pump clicks off itself) i'm just at the full mark, then when it gets to half a tank it'll start acting weird, sometimes going to empty and putting the low fuel light on, then gong to half and then settling at whatever mark it's actually at