Ok, so I removed a Raven inverted oil system. I put plugs in the bottom of the oil pan and in the back of the engine where the inverted system hooked up. I also put a new oil screen and oil screen plug in the back of the engine. I then replenished the oil with 7 quarts of oil and started the engine. No oil pressure after 30 seconds. Shut down and wondering what the problem is. I did check the oil pressure sender and it is functioning correctly. A friend suggested I have to prime the oil pump? Any other suggestion are welcome.