Gas pump shut off

The gas pump keeps shutting off when I try to fill my '95 Saturn, like it would when the tank is full, even when the tank is empty. This is a recent phenomenon, and it does it at every gas pump. I have to keep pulling the handle to get gas in the tank. I took off the filler tube and checked both it and the vent line. Both are clear. What could be causing this?

Defective evap vent valve or filler neck assembly

I think the Saturn’s are a non-pressurized evap system. The link below might be of some help about what might be the cause.

"Evaporative emission systems perform a few simple functions. Venting the fuel tank when needed and disposing of the fumes are the primary purposes. They use an incredible amount of complexity to address these tasks, largely due to Government regulation. This leads to many check engine lights, perhaps more than any other system on the vehicle. "

http://www.agcoauto.com/content/news/p2_articleid/294

For a pressureized evap system like on Chryslers or many German cars …

http://www.agcoauto.com/content/news/p2_articleid/295