under the injector. I've never seen a "copper sleeve" and I don't know about your engine. The "puff of smoke" is likely atomized fuel seeping from the bottom of the injector. If you have a new seal with your spare injector I would remove the old injector and replace it and it's seal. If it's anything like mine I would remove the return line from the top of the injector, loosen the (usually) two nuts holding the injector into the head and tap the side of the injector lightly with the wooden end of a hammer. I would then take a shop vacuum cleaner and vacuum out the base of the injector as a precaution while attempting to remove the injector by turning it with a pair of channel lock type pliers. Alternate tapping and turning until it brakes free. Vacuum and remove anything loose before removing. Once you get it loose I would remove the injector and replace it with your spare. If the new copper washer is not available, using a flat file and sand paper I would file the old ridges off the existing copper washer and replace it. I'd then re-tighten the injector and return line. Then I would carry a spare set of injector and return line washers to use in just such a situation. I think it's a simple fix once you get the new washers or seal. Let us know. Good luck.