I am working on a 1987 E 350 motor home it has a 460 with a holley 4 barrel carb and a electric pusher pump in the tank. The problem is the gauge only goes up to just below the empty mark, the tank is full of gas and the sending unit was supposedly changed. I changed to a spare gauge cluster and the same thing.I pulled the plug off of the sending unit and checked voltage and it was bounsing all over the place, so I put a test lite on it and it was pulsing ,what the heck is goig on????HELP P.S. I also had the same pulsing at the plug end under the hood with the connection together.