I have built a 4-level pump stack, like this one from the wiki, just without the top level.
I have doublechecked that there is an open space tile below the impenetrable pump tile. There really is, on all levels, except for the lowest.
Now I wanted to try this pump stack running dry, pumping air before I flood it. I have one dwarf powering the lowest pump. The lowest pump is animated, but the pump directly above it stands still. It says it needs 80 power but is getting 0 power. The k-cursor clearly shows open space below the output end of the pump and floor below the input end.
What am I doing wrong? Does this sort of pump stack work at all? I think I had it working once in a 34.x version, but didn't try since then.
I hope that the dwarf sitting at the input end of the lowest level is not somehow blocking the power transmission, because the open space through which the power should propagate is directly above his head.