Try cranking the engine with the ignition leads off. This will hopefully prime the oil pump. Are the lines attached correctly? In stock condition they can't be swapped but if yours is different? Is oil making it to the pan below the engine? Unscrew the drain plug and it should flow. Are the oring seals in the oil pump where they belong? It is like anything, figure out how it should work, check the easy, external stuff first, then dig as deep as you need to to find the problem. Godspeed.