Check the cousin metals, they must already be very scratched or worn, just for you to realize, check of connecting rods and bench, do not take a long time and you will realize if you lose pressure, or, if you have an oil pump (the ones you use to put or remove the oil to the tranmissions) Adapt it where the oil vulvo goes, start pumping oil out there and removes the crankship so that you see the oil. Let's put to think a little, the lubrication system on the engines, is given by ... the oil pump, the filter, the oil pipelines, the ducts in the rod and bench metals, you already changed the pump, analyze and tell me more you are missing, more than check the metals, or some diver that is damaged and it is not to check the valve regulatory valve of the pressure regulating of the filter. You have no other than exhaust all possible causes.