I'm not sure about the Jeep, but the last few oil pumps I'd looked at were basically just two intermeshing gears. I suppose if the gears were ground down, yeah, it could grind. I don't find that very plausable, though, since it'd take a long time for them to grind down that far and I believe the engine would seize first. But trust me, if you had 0 oil pressure, you would know in a big hurry. It wouldn't tick, it'd be making loud clanking noises.