The sump that receives the discharge from the laundry tub and floor drain needs to have a lid and be vented and tied into the existing vent system. Since it receives the discharge from plumbing fixtures, and is tied into the waste system, there's always the opportunity for sewer gas to back up into the pit from the sewer system. Many times the check valve (there should be one on the riser from the pump) gets stuck open due to lint and debris from the washer. This allows sewer gas to come back down the line when the wind is blowing or a toilet flushes (since water inserted into the plumbing system pressurizes the system ahead of the water). If there is no check valve on the floor drains and on the sewage ejector, you may have to install them. But there does need to be a sealed lid on the sump basket to keep the smells out of the basement.