Vent line question on 1970 Dart

NO!! It is exactly as described, please read again. It runs along the main filler tube, down through the filler tube gromment, and OPEN ends inside the rear frame rail. THAT IS the vent and MUST be open to atmosphere.

You car either does not have the evap control system, and has been conerted to the old style vent, OR ELSE it came this way from the factory. Only CA vehicles in 70 had the evap control vent

Please download a service manual from MyMopar. Get into the fuel section and the emissions system chapters, and it is all laid out