71 gas tank??

[BobbyFord]

If the gas tank could not vent, would that cause an engine to shut off?

Yes. Mine shut off at 1/2 tank because the charcoal canister vent line was plugged and the pump could not suction any more fuel from a sealed fuel tank.

[max_alberta]

Rather than start a new threat, since my question is similar, I'll ask it here.

Truck had an aftermarket locking gas cap, whose seal failed. I did a lot of driving one day, and ended up with gas running down side of cab. Bought new cap at NAPA, and seals well - maybe too well, when I take it off, I hear a big pressure release. Today folded the seat forward and noticed top of fuel tank around fuel line connection and tank level sensor was moist with gas.

Truck is 1969 F-250 with a bunch of 1971 parts in it. Gas tank is non-vented style.

Going to replace gasket for level sensor, but wonder if the new gas cap caused the seal to leak.

Is it normal to have a lot of pressure build up in the tank when driving? I'm glad I don't smoke anymore!

[Whateverman]

yeah, its normal to have pressure build up with a sealed cap,especially if its warmer than when you filled the tank ( conversely, it will also create a suction if the temperature drops)
the fact that the tank was pressurized again probably came as quite a shock to those crusty old gaskets