I think when Jack is grief-stricken and conflicted, he just ceases to think things through. He's so used to grinning and blustering along when he doesn't really know what else to do for a situation.

Yeah...really crap idea, Jack...lucky it didn't last long. ;)

Ianto may not need to have words. A cup or two of Owen's coffee may well do the trick.

Owen knew better than to go near the machine while he was alive.
Why would he go there now.

Ianto gets that Owen is fragile, but there is other things he can do.