I've been looking into re-connecting the return lines in mine. The vent (smaller metal line) was plugged when I bought it and the return line was wide open. I filled the tank a week ago and after driving for ten minutes I noticed gas running out of the open return line under the hood. I plugged it and have been driving it like that for a while. I've decided to reconnect it to something, so I bought the 3 way filter and a check valve. I no longer have a charcoal canister (po removed it). I suppose it's ok to use this in-line valve from BMW, PN#16 14 9 068 988? Was going to run the top hole of the filter to the check valve and then to the open return line. I haven't had any issues with starting, though.
The plugged vent is why the gas came out of the return line.
Gas in an underground tank is a constant temperature, within a few degrees of the mean yearly temperature of wherever you live.
In a normal mid-latitude area where the ground is 58* the cold gas gets pumped into your tank and absorbs heat and expands as it reaches ambient temperature. (The vapor expands more than the liquid.) Without the vent line the pressure is forced out somewhere else, at a lower connection in the tank than the vent line, a connection in the liquid gas.
Sometimes the gas cap leaks enough to allow air in, sometimes it doesn't, but even a basic mechanical fuel pump can create enough suction to collapse a fuel tank.
Plugging up the vent is just a problem waiting to happen.
I haven't a clue why someone would remove a charcoal canister. It provides no performance gain to remove it and makes your car smell like gas on a hot day. It allows moisture, dirt, and insects a direct route into the tank. It creates the possibility that liquid fuel may drip onto a hot exhaust.
Even without the vacuum purge working it does most of its intended functions.
Topic: 1/4 check valve (Read 5556 times)