Brand of the primer? Sketch or picture unless too hard to get at. Or, purchased from??? Spruce?
A "dry" suck is suggestive of a misconnect, as though the output and input are reversed. If I am successful in including a picture of my Kohler primer, the hard-to-see "INPUT" is positioned such that either fitting could be taken as the input.
Let us see if this works.
True to form, the next step for attaching a picture did not work. I tested the primer and found that one can sense a vacuum when the plunger is withdrawn and one can sense a harder pull when the input is blocked and one can sense a tiny puff when the plunger is pushed in rapidly. With two of you, one at the disconnected end at the gascolator and you pulling, you could prove the same.
Later, a different option appeared below the text portion and it looks like the image is attached. Open in microsoft phote editor and expand by moving the wheel on the mouse.
Files Attachment(s):Primer trimmed.jpg