A Beech 1900 departed the gate for flight. The crew was unable to positively determine the wing tank fuel cap status and so returned to the ramp where the fuel caps were found to be not installed.

Narrative

I was the Captain on flight; the aircraft had just been brought in and the flight was running late due to a delay with the passenger manifest. After engine start I pulled out of the parking spot and held short of the taxiway while the before taxi checklist was run. Upon reaching the point in the checklist to verify fuel caps where in place I looked out my window to check. At this point there was doubt in my mind that the cap on the left wing was in place. Rather than turn back at that point I made the decision to continue with the rest of the checklist with the intention of returning to the issue; before continuing to depart. After completion of the checklist I consulted with the First Officer to verify whether or not there was a fuel cap on the right wing; he also had doubt. It was difficult to be sure if there were caps on the fuel tanks or not. Rather than continue with the flight I made the decision to return to the hangar to be sure. Upon reaching the hanger the missing fuel caps were verified.