FYI I just put one in my Carden Extra.

I recommend two check valves, one on either end of the smoke pump. That way the fluid cannot go back into the tank from the pump. I've used this on a Slimline, a Skywriter, and a TME and they all worked fine as far as prime is concerned. I actually over kill mine, on my 106 I put a check valve behind each muffler, as well as a check valve behind the pump. Check out Carden's site to see my 330 pumpin' smoke through some maneuvers.

That would be my only thought, but also do check to make sure something crazy didn't happen like the clunk fell off or something.

If you'd like to move the tank around that's OK I guess but a lot of work (or potentially redesign). It may help to move the pump to be inline with the tank on a vertical plane to, to avoid any gravity feed issues.