A fluid system coupler includes a coupler body having an open end for receiving an adaptor therein. A seal assembly is movably disposed within the coupler body for selective sealing engagement with an adaptor. Lever cams pivot into or out of slots in the coupler body between locked and unlocked positions to fasten or unfasten the adaptor to the coupler. A handle is movably connected to the coupler body. Movement of the handle moves the seal assembly within the coupler body. Movement of the handle also results in movement of the lever cams between the locked and unlocked positions. A poppet assembly is mounted to the seal assembly. The poppet assembly can selectively open or close a fluid passageway through the coupler.