One of the first symptoms commonly associated with a bad or failing fuel filler neck is the fuel smell. While a faint fuel smell when filling up is normal, if the smell lingers or becomes stronger over time that could be a sign that the fuel filler neck may have a small leak.
 
As you all may know, there are two different options. A long neck filler pipe (non tii) for 2002's (03/1966 - 04/1971) and a short neck for 2002's (04/1971 - 07/1977) and for ALL tii's and Turbos! Is very important to use the correct filler neck for the tank you have