Unique gas tank vent problem '96 brighton

[dimwittedmoose51]

'96 Brighton wagon rust belt car, 170k. I spent a month getting around to replacing the rusted gas tank and rear brake line with a like new brake line from a pick and pull AND A GOOD USED GAS TANK FROM THE SAME PLACE(DIFFERENT CAR). When I finally got everything put back together and tried to start the engine, it wouldn't start. That turned out to be having the return and pressurized hoses hooked up bass ackards where everything goes into the body on the driver's side. With maybe 1/4 tank of gas in the tank, I came back out after I had gotten the car to run and found fuel dripping from under the radiator. Got a pan under that and traced the problem down to a hose coming out the back of the charcoal canister. I went back and unscrewed the gas cap and there was a tremendous amount of pressure inside the tank, leading me to believe that something wasn't venting properly.. No question my canister is likely toast now after being soaked with gas, but what could have caused this?? I had no troubles before the tank swap. I'm surviving for the time being by only driving wit ha half tank of gas at a time and leaving the gas cap partially unscrewed while driving.

 

I understand there's a butt load of plumbing to trace all this down with, but have any of you come up with a tracing format to find out where the problem is?? I replaced all the rubber lines on top of the tank and blew compressed air through all the metal ones while they were disconnected. Both of the top vent valves appeared to be working too. unless I pinched a hose getting the new used tank up in the cavity, I can't think of any other casue that might have occurred. I have a Mighty Vac I could use for either suction or pressure, but need some guidance s to where to look and troubleshoot. I also know that Subaru was constantly changing this system throughout the 90's and that's not helping matters either.

 

TIA

 

DM&FS