First- - - -put a good gauge on it! The idiot light turns off at 7 pounds of pressure, so even a tiny bit of pressure will turn the light off. Next, drop the oil pan and pump again, and pack the cavity around the gears with Vaseline. I've seen numerous situations where a good pump got air-locked and wouldn't pump. While you're into the pump, be absolutely sure the relief valve is closing fully. Also, be sure the wire to the idiot light isn't shorted to ground anywhere. The switch provides the ground for the light, so any other contact with ground will make the light stay lit, even with good oil pressure.
BTW, DON'T use heavy grease, like wheel bearing grease, to pack the pump. It can clog passages elsewhere in the system, and cause bearing damage. The petroleum jelly dissolves completely when oil hits it, and won't create problems.
Jerry
