cause of pressurized fuel tank?

[TDS-MN]

well, the emissions system on the truck is pretty passive. No computer, so it just has cat converter and charcoal canister, and AIR pump. Hopefully I'll get a chance to look at it this weekend if the rain holds off. Should be something I can easily bypass for testing purposes at least.

As predicted, now that I have the gas cap loose, I was able to drive the 18 miles home, and no dripping when I parked.

Interesting mention of the fuel pump. I did replace that last year, but don't recall how many hose ports it might have had. Will take a look, for what it's worth. I THINK that I had this issue even before that time, but am not 100% sure anymore.

Thanks for the other ideas though.