gas vapor part in 1971 280SE

[spatengal]

Good Afternoon again!
Again I am trying to get a 1971 280SE running after 13 years in the barn. I did get all the rat---- out of it!!. In the trunk there is a plastic part that has 3 small hoses attached. 2 run to the fill spout for the gas I am guessing for vapor but the 3rd is not hooked to anything so the trunk smells like gas. Can anyone tell me where the 3rd hose attaches? Why do I need the part I could just vent the tank to the ground?
Thanks
Pam

[meltedpanda]

If you are talking about the "black box" that sits in the wheelwell area then you are correct
If I recall that vents out of the wheel well somewhere to the outside. The line sometimes decays and becomes shortened and the reason it ends up in the trunk

[Shortsguy1]

On my 220d, the third line runs to a little rubber port that hides behind the bumper at the passenger side rear corner of the car. Perhaps yours is similar. It is visible of you look for it behind the bumper, but you might not notice it otherwise. I think that the black plastic box is designed to capture any liquids that might get forced up the vent lines (when parked on an incline or on a road with a lot of crown). I had mine still hooked up, but not at a high enough location in the trunk. And liquid diesel would get leaked out of the little port that I mentioned above. With the black box higher in the trunk, no liquid diesel ever leaks out of the port. So I would discourage you from simply venting to ground, because you will probably have a gas leak as a result. Leaking diesel is not great for the environment, but leaking gasoline could be a real safety concern.