Ford E250 Fuel filling Problem

I have a 04 Ford E250 Van. Recently we started having trouble filling it with fuel. The gas pumps keep shutting off and you have to fill it slow. We checked the funnel, blew out the vent, removed the hose & checked it,removed the valve and checked it, switched funnels with another van. None of these fixes seemed to work. Does anyone have any ideas on what may be causing the problem?

Between the filler neck and the tank is an “anti-rollover check valve” a ball in a cage type thing. Did you find that? They can stick in the closed position. The cure is to remove the ball…