2008 Ford E-Series Van gas filling

While putting gas in our van the gas pump shuts off as if we have a full tank. No matter how slow I try to fill the tank, the pump shuts off. I can't put more than about.50 cents worth of gas in, the pump shuts off, I let go of the handle, squeeze it again to get another.50 cents. This van did not do this when we bought it a couple years ago. We've been putting up with it for about 6 months. It takes about a half hour to get a full tank of gas. This is my wife's vehicle and this problem is driving her nuts, and she's starting to drive me nuts because she wants it fixed. Please help. - Jeff