I've never watched the bubbles to see if it does it Everytime. It might just bubble until it's caught-up. I guess you're saying that you're getting Dry hits? Either try sucking w/o power to draw more fluid in, or finish the
tank and put another hole in it. Some people have 3-4 holes.
What kind of carto? What kind of tank? What mix of
juice(pg-vg)?
If you have a side-fill tank, you can loosen or remove the screw and it will get wet quick.