B767-200
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed
Aircraft; Human Factors; Procedure
We departed ZZZ turned northwest and was climbing out of approximately 14;000 ft. for 16;000 when we received an EICAS MESSAGE L FWD ENTRY DOOR. Also entry doors light was illuminated on the overhead panel. We seemed to be pressurizing normal but it seemed slightly louder than normal.  At this time we where level at 16;000 ft. so I informed ATC that we would like to stay at 16;000 while we look at a pressurization issue. I read the QRH and it advised that if pressurizing normal that we could continue but if not we need to raise cabin altitude to 9500 ft. and land. At this point it seemed we where pressurizing but I didn't want to climb higher without being certain so I got out of my seat and went to the back of the plane to look at the door. I immediately could see the handle was about 1/4 open; lock was released; some daylight under the door and could hear whistling noise of air escaping. I returned to me seat and informed ATC that we wanted to descend to 10;000 ft. I then called and received a phone patch to flight control. I told them we have an entry door unlatched and need to land. I asked if they wanted me to return to ZZZ; ZZZ1 or ZZZ2 since they where all about the same distance. We then informed ATC that we wanted to return to ZZZ. We finished the remainder of the checklists and returned without incident.
767 Captain reported aircraft failed to pressurize correctly and discovered a Service door was not closed; resulting in an air turn back and precautionary landing.