The fuel gauge in my 98 GMC Z-71 is not working properly. After talking to various people, I decided to replace my fuel pump. When I started it up, the fuel pump noise was considerably less than before, but the fuel gauge still "vibrates". It reads the approx. amount of fuel, but it's not a constant gauge. A few months ago, I decided since the fuel pump is still under warranty, I would change it again, this time I took the bed off (instead of dropping the tank) where I found that my ground wire to the pump did not have clean contact to the frame. I cleaned the grounding point and thought I solved the problem, but after putting everything back together, the gauge still shakes. Any advice?