I bought a 48k JY 1999 5.9 engine in January and went to get it ready to start and cannot get oil pressure. not even a little. So here is what I have done:

Way back in March I swapped oil pans b/c oil one was rusty. Put 5 quarts in , took distributor drive out and used 5/16 hex on my big 1/2 hp drill clockwise to prime it. Never got pressure, but oil very VERY weakly oozed from lifters- no improvement even with turning engine. So i took oil filter off and put drill on and oil cam gushing out of the where the oil filter mounts, as it should. I figured it was air locked and would catch with my normal procedure for tough engines- overfill by 5 quarts and take plugs out and crank .

Did that yesterday and no reading on my mechanical gauge, which is working and accurate on my 88 and 93 trucks. So despite that I already inspected the pump pickup and distributor drive, I changed oil pumps figuring there must be a crack in the pickup I did not see. I tested old pump with drill- it pumped fine. I tested new pump- it was fine

I also hand turned engine before this and the camshaft is not broken. I put a new timing set on it and did not move cam or crank- keyways were perfect- no shearing. Engine sat in my barn in january and February but was buttoned up- no way could a mouse crawled into the galleys as the filter was on it the whole time

I called company and they sent me a video of the engine running before they pulled it and it was running and clearly shows 50 psi on the factory gauge.

I'm out of ideas and need help now. 2 pumps and 2 pickups would suggest its not a pump or bottoming out on the oil pan issue. Chnaged filters with no luck.

All suggestions welcome