[urq] Fuel tank vent issues?

[Jon Archibald]

Hi, been driving my car (85 w/3b) to work this week. Today on the way home
the car simply died at a stoplight. I was able to get it to restart but had
to feather the throttle to keep it on while it ran roughly, similar to when
I had a high pressure fuel line rupture. Made it home at which point it
then idled fine. Decided to get some fresh gas (it was down to about 1/8)
and when I opened the gas cap it went POOF! Releasing pressurized air.
Drove the few miles home and opened the gas cap again, no poof.

Questions:
1) Is this likely a failure of the little check valve just over the tank?
Would pressure buildup in the tank cause the stall? If so why did it come
back to life after nursing along for 1/4 mile?

2)I'm assuming dangerous to drive this way until I get it figured out?

I would like to drive the car until the weekend, but have a feeling I
should park it until I get to the bottom of this.

Any halp appreciated.

-Jon