Fume problem

[zmann]

I have an '81 280zx and sometimes I have a terrible gas smell and sometimes not. I have had three different mechanics check it and nothing is found. One put a dye in the gas tank and found nothing. I know that when you fill the tank, there are sometimes problems, but this is not the situation here. I would be grateful to anyone because it is a really frustrating problem

[SteveJ]

Inspect any vent hoses and the filler tube.