Filled gas tank full for the first time I owned it and it's leaking!! Wtf

[9t3lightning]

Group
Own a 90 wagon that I've been driving daily for about 3 months now .
Today I filled the tank full since I owned it, and tonight I smell and see fuel dripping down the side near the filler neck.
Now with a full tank of gas ugh, where do I start..

[sly]

first... run it down to where it stops leaking so you know you won't flood yourself with gas when you pull the filler neck to replace the grommet. That should be all you need. You may have to loosen the straps on the tank to get it to drop a little on that side for clearance due to the wagon body seams. You may have to drop the tank to get the neck out completely. I don't know where to get the grommet though since I have sedans... I think it's the same one, but I could be mistaken.

[gadget73]

yep, start by driving

[BerniniCaCO3]

I had this same problem! Twice...
Don't panic. You'll lose a few bucks of fuel until the level drops. Nothing back there to start a fire. Oh well.

The grommet was still carried by ford dealers 2 years ago, anyway. Came in a pack of 2 for like $10. Special order of course.
I dropped the fuel tank, put it back up with the original grommet, and had this leak.
Replaced the grommet, still had the leak, so I simply kept it to 3/4 tank at most.
Just recently I redid the pump seal and reseated the evap grommet (I SHOULD have replaced, but didn't) and it seems to work, so it was one of those.

The filler neck is WEDGED in there. You might have to loosen the tank straps a little to get the angle right. Have a pry bar, and turn turn turn as you tug on it to slowly ease the filler pipe out. Or maybe try slicing the grommet.
The new one is even more firm (tighter fit than the old stretched one). Get some silicone lube, the grease, and apply liberally. Use a rubber mallet to get the pipe back in.

Possibility 2 is that the fuel is coming out of the evap fitting on top.
Either the fitting is loose,
Or the tank is overfilled.
Or as I found out, the fitting was loose, causing the pump at the gas station to overfill all the way to the top, so it did come out there (and happened to run down the side, over to the filler pipe).
To explain, a gas pump automatically shuts off based on vapor pressure. A full tank will have a higher vapor pressure, and the pump clicks off.

If the evap fitting is loose, and it's just popped into a grommet like the pcv valve-- then the vapor can vent rapidly through that hole, pressure won't build up, and the pump doesn't shut off until gas is all the way up the filler pipe. Or if there's any other hole, like a rust hole, in your tank! The same symptoms will apply. The gas pump won't shut off until it's much fuller than it ought to be.

You can try to find the hole it's venting through, be it pump seal, level sending unit seal, filler neck grommet, evap grommet, or a rust hole,
or you can just live with it and know that, for example, maybe on 1/4 tank you only want to add 12 gallons (figure it out for your own car) or else it'll start leaking out the top of the tank.
I had to do this with another car, my sister's mercury tracer, where the evap switch for venting was stuck open (slightly different setup) and no gas station's pump would shut off.
On my own car, a 1990 colony park, it turned out to be the evap plug that I hadn't put all the way in correctly, or else it had worked its way out, since I'd replaced the gas tank.

There's also a fuel return line over the frame next to the filler neck. Pressure line is on the passenger side. Could that be rusted through/ the rubber rotted through, and it's dripping from there?

[Lincolnmania]

yea filler neck seal is bad, or the tank is rotted and cannot take the weight of a full tank.