[trevzor4242]

1991 CRX HF. Put a D16 in it last summer but I kept the charcoal can and all that crap. Haven't modified the fuel system as far as I know.

At my last track day I noticed some fuel smell in the car but found no leaks and went on with it. Trailered it home and parked it - 99% sure I did not fill up the tank after the track day.
Today, a week later, I took it for gas, and upon removal of the cap I heard a hissing. Shortly after I put 1/10 a gallon of fuel in and it overflowed. I sat and watched it keep overflowing for over 5 minutes til I just put the cap on and went home. At home, I removed the cap and it hissed like before.

Any ideas what this could be?
A description or schematic of the EVAP system would be super helpful. I have never messed with these systems but I'm an engineering student and want to figure it out.
I don't want to bother troubleshooting til I understand what I'm working with, so I'm off to research that. I know to search, and I will, but I'm hoping someone with more knowledge may offer feedback on the specific situation.

Any advice, tips, descriptions are much appreciated. Thanks!

 

[JamesCRX]

I'm spitballing here, but I had a similar problem when I bought mine: tons of hissing when I removed the fill cap, and even gas leaking out of the filler when the tank is full on a warm day.
The problem with mine was the activated carbon canister was hooked up backwards, preventing it from venting through it and pressurizing the tank. Not sure if that's the same cause as yours, but it's worth a look. If the canister is blocked in some other way it could cause the same issue.

 

[trevzor4242]

I'm spitballing here, but I had a similar problem when I bought mine: tons of hissing when I removed the fill cap, and even gas leaking out of the filler when the tank is full on a warm day.
The problem with mine was the activated carbon canister was hooked up backwards, preventing it from venting through it and pressurizing the tank. Not sure if that's the same cause as yours, but it's worth a look. If the canister is blocked in some other way it could cause the same issue.

Will check it out! Thanks
I just picked up a parts car that has a charcoal can so I may try that in a last ditch effort as well.