What is the function of the 2 plastic canisters hanging from the radiator?

Actually my larger question has to do with the sudden onset of rough running with my '83 400i automatic, and what I'm looking for is the solution to this problem.

The story begins with the information that the car had been inoperable for about six weeks, as I was getting a rebuild of the hoses running to and from the oil cooler. Removal of these hoses required the removal of the plastic canisters, so I could move the puller radiator fan out of the way. Yesterday I got everything put back together and now the engine runs really badly. In a desperation move I went to the nearest filling station, as the fuel level was low and I thought (hoped) that fuel starvation might be the cause of the rough running. When I unscrewed the gas cap, air -- and an aerosol of fuel -- blew out of the filler neck. This had never happened before!

I had run the car in the driveway at idle for quite awhile -- 15 minutes at least -- checking for leaks, before I had sputtered my way down the filling station. Obviously the fuel tank got pressurized. It was not a hot day -- just 70 degrees Fahrenheit -- so hot fumes in the tank were not the cause. The reason I'm asking about the canisters is that the connections for the fattest hoses running to the canisters say "Fuel Tank." See the second photo below. They are routed from a T-connector to a single hose which disappears under the K-Jet assembly on the driver side. Based on the words "Fuel Tank" at the connection points on the cannisters, I am guessing that this single hose runs to the fuel tanks.

The connection points for the other two hoses are labelled "PCV" and "Carb." As the third photo shows, The "Carb" hose is T-eed into a line which runs from the throttle inlet, above the throttle butterfly, to the bottom of the WUR. The "PCV" hose is T-eed into a line which runs from the exhaust cam cover to the top of the WUR. My theory is that the "Carb" hose should be a very mild vacuum source, and that the circular connector at the top of the canister should route that vacuum to the Fuel Tank and to the cam cover -- i.e., to the crankcase. The purpose of this arrangement would be to route fumes from the fuel tank and from the crankcase into the intake stream, above the throttle blades.

Is this correct? If it is, then what is the cause of (a) my sudden rough running and (b) the pressurized fuel tank?
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Thanks for the responses. I have an update, that I started up the car today and let it warm up and the rough running did not return. I drove just a little, only till the oil temp started to move, and I ran the car to 5000 in 1st and it seems to be running just fine. I drove no further because a peek under the front valance to check for leaks revealed a drip of red ATF about even with the front wheel on the passenger side. I think one of the hard lines for the transmission cooler has sprung a leak. But the rough running seems to be gone. There must have been some connection with the pressurized fuel tank. But if it doesn't happen again I may never know.