I started my car today and let it idle for about 5 minutes. During that time the gas gauge went from 1/2 a tank to a quarter of a tank. There are no obvious leaks and the carb was worked on a few months ago. I do not drive it very often so I cannot tell you if this is a new or old problem. I am assuming it is a gauge reading error but I am not sure where the problems lies (ie sending unit?). Any suggestions as to how to trouble shoot this problem? Is this an easy fix? If it is a fuel sending unit does the gas tank have to be removed? Thanks.