I have 96 sierra 2500 7.4. It has just under 79000 original km. I noticed the other day the fuel gage stopped working. I climbed under to have a look and noticed that the fuel pump is buzzing loud enough to hear over the motor while sitting in the truck with a window open. I'm not sure if it should be doing that full time or just at start up. Does any one know why or what I should do?