I have a 1993 chrysler fifth avenue with a 3.8 liter engine. There is no oil getting to the left (#1 piston sice or side closest to firewall) side of the engine. I took the covers off and the front is lubed fine, the back dry and it sounds like a lifter, but not all the lifters could have gone bad on one side, and none on the other side. There is no oil pressure, tried replacing the oil pump but no change. What could cause this? Oil pressure regulator of some kind??