Next time your gonna change your pumps oil, if you have a compressor, remove drain plug, blow air through the dip stick hole. 15-25 psi. Takes 1-2 mins to drain completely and you get more to drain than gravity alone.
If it's a general and pulsating is the only problem i would definitley start by removing and inspectingthe valves. Any crap that gets lodged in the valves will cause baad pulsating. Or if the valves are pitted or worn out