What causes oil to not flow to the engine if the oil pump is fine? on 1997 Buick Skylark

Replaced the head set, one of the intake valves, and the push rod which were broken and the engine is still very noisy. When we checked the oil filter there was no oil in it. So than we checked the oil pump and it was fine too. What would cause the oil to not be circulated in the motor if the oil pump was fine?

Asked by for the 1997 Buick Skylark
how did you check the pump???? did you pull out the oil drive rod under the throttle body??

Yes we did pull out the oil drive rod. Do you think it might have broke up inside the throttle body?Also we turned the old oil pump and it seemed to move the same way that the new one did that we bought so we still aren't 100 percent sure that the oil pump is good. What is the proper way to test the oil pump after it has been taken off the car?
oil pump is inside the oil pan. you need to do a manual test with a gauge to confirm. let a shop do this for you to confirm