Sometimes it takes a good six or seven puffs to get them going. More if they were originally a bit overfilled.
It isn't good when they leak - you either end up with liquid in your mouth or in the battery. Both of which are bad!!! The only time I have had an issue is when I have refilled and I have overfilled.
My pre-filled ones are normally good.
I hope they work out for you. I love cartomizers for driving and at other times when it is inconvenient to fiddle.
I forgot to ask... are you getting any air flow through the cartomizer when it is screwed onto the screwdriver?