My truck keeps "running out of gas" while driving. This will happen when there is close to a 1/4 tank left. Its never done this before, until this week. It left me stranded this morning and late to work. Each time I can add about a gallon of gas to it and it will start right back up and run fine. Before adding gas I tried just removing the gas cap to make sure there was no vacuum. This has happened 3 times now in the past 4 days. Could this be a fuel pump? The truck has 55k miles on it. Any help would be greatly appreciated.