I have had problems for years. He needs to remove the sending unit, presure wash the bottom of the tank and vacuum it out. The right way is to cut the lid off and epoxy the whole tank. You can check to see if your having a problem by removing the fuel fiter and see if there are gold color pieces of epoxy. It looks like strips of varnish when it peels. It is the worst design in the world. Once you fix it right you should be ok.