A
scroll compressor that utilizes liquid or vapor injection to cool a
working fluid being compressed by an orbiting scroll member and a non-orbiting scroll member, and / or to increase the efficiency of the compressor. An injection fitting is secured to, and extends through, the compressor housing and receives liquid or vapor
working fluid from a source external to the compressor. The non-orbiting scroll member may be fixedly mounted with respect to the
crankcase of the compressor, and internal passages formed within the
crankcase and the non-orbiting scroll member, which are substantially isolated from the suction pressure and
discharge pressure chambers of the compressor, are used to convey liquid or vapor
working fluid from the injection fitting into
intermediate pressure working pockets defined between the scroll members. The compressor may include an end cap fitted over an open end of its housing which overlaps an end of the passage provided in the non-orbiting scroll member to provide a robust sealing of the passage.