Hard time filling fuel

2000 astro 135k van runs fine. No codes. Hard to refuel. Keeps backing up the filler neck. Tried many different gas station pumps. Tried fueling with van running and not. Gas gage hasn't worked in awhile so it's getting tricky to figure how much gas is in there. I. Going to replace the sending unit in the spring but need to get through winter with being able to refuel. Could it be my charcoal canister? Any suggestions or tests would be appreciated

I would guess that the problem is in the filler neck anti-siphon/anti-surge assembly. The filler tube assembly can be removed with the fuel tank in place, but the tank is going to be less than half full of fuel to avoid spillage. Removal will be good practice for dropping the fuel tank to replace the sending unit, which is likely what it will take to get the gauge functioning again.

This is the assembly at the tank end:

http://www.wwdsltd.com/files/M-BodyFuelFillTube.jpg