Gas tank riddle Options

[Porschef]

The PO had the tank cleaned and resealed, but I'm puzzled by what's happening- the hose connection (charcoal canister, perhaps) by the fill was disconnected when I got the car. I assumed it had just been disconnected somehow and so I reconnected it. Just so happened that I had the car running in the driveway, checking some other stuff. Shortly thereafter, I noticed the fuel pump making a strange sound. I didn't know what to do, other than undo the last thing I did on the car. Turns out the tank has quite a bit of vacuum. I didn't realize it until after I had pulled the hose off, and started to hear the tank expand back into it's original shape. Removing the gas cap relieved even more pressure quickly. The pump then quieted, and all has been ok since.

Does this sound like a pinched return line? If so, would it cause a rich condition?

Thanks in advance,

Joe

[Andyrew]

Tthe charcoal canister is just a smog thing.. return the fuel vapors back to the intake... Most people just leave it unplugged.