If there is a problem with the jet down the hole, that would cause a problem. Did you clean the jet? Does your pump pump water, but just at a much lower pressure or flow than it should? Or does it not deliver water?
I don't know how you detect holding prime or not. Do you say that because the pump pumps a little, or because you can pour water from up top without it dropping? I would think leaky leathers would let water go back into the well.
I really have no experience with jet pumps, and I don't feel very confident in understanding them.