I don,t really know what your problem is but am interested in knowing how long you have had the truck in running condition. I have a 65 chevy truck and it did the same thing and like to have drove me nuts. I found out that even thogh i had pulled the gas tank and cleaned it that i still had a problem with the pickup tube. I had to replace the tube to clear the problem. Good luck in finding your problem. Hope someone else can give more help than i can.