Very odd tank fill-up problem

My dad's 91' Lesabre Custom has just started giving him quite a strange problem at the pump: when filling up, the pump will ckick off, as if the tank were full. At the initial time he attempted adding gas, he only had about 1/4 tank in there. He thought maybe the pump he was using was defective, so he tried using another only to get the same problem. He had to constantly pump the handle with his had because it'd constantly shut off within 2 seconds.
For an added check, he tried filling up at a different station, but the problem persisted.
He also noted that there is a gas smell around the car in his driveway.
I was thinking there must be some back pressure (for unknown reasons) causing the gas pumps to sense a full tank. Any ideas? About a week earlier I had replaced his fuel filter and pcv valve, could this be relevant to the problem? I started the car and checked for leaks around the filter after replacing it, and none were visible. I've replaced dozens of fuel filters but never had nor heard of a problem like this! Thanks all!

You need to check for an obstruction in the neck of the gas tank.

I've had that problem on occasion before. I found that not putting the nozzle in all the way helped.:2cents:

Sounds like a plumbing problem. It must be air-locking. I have had that problem on some older vehicles. There is a separate, smaller hose that goes from the neck to the tank. It is for the purpose of releasing the air, so that the tank will fill, like plumbing air/roof vents on a house. The air vent hose may be kinked or blocked as mentioned, so that gas can't enter the tank and the pump kicks off. It may help to hold the pump up higher so that it can vent through the fill tube. I think the opening is fairly small though and that may not improve things much. Look for a kinked air vent hose or something is in the tube blocking the air flow.

I'll look into everything mentioned. Thanks all!