Get a new cartomizer. Repoke the holes gently (with a paperclip) so the polyfill has enough wiggle room for the juice to flow in. Saturate the cartomizer (don't know how you do it, but if it's filling from the top, fill to the sides, not the middle, about 20 drops, a couple of drops, then wait for it to be absorbed, then repeat), stick it the tank, fill the tank on it's side with juice avoiding the middle of the carto, secure the cartomizer to the tank, take a few dry pulls (vape with no power) to see if there are any more bubbles that are visible with each drag, if no more bubbles, vape with power starting at 3.4 volts, then increase as desired. Take light pulls/draws until the cartomizer is broken in.
Vape no higher than 3.8 volts.
You have a dual coil cartomizer rated at 1.5ohms (two 3.0 ohm coils in parallel)
UDCT = tank with a locking ring for flanged cartomizers (cartomizers with wings)
Cartomizer = metal tube that has polyfill and coils
Hope that helps.