If you review the manual that was sent to you, you will see that it requires a special tool to remove and install. You can substitute the special tool with a bolt (I think they are 6mm) and pull it out with a set of vice grips. You need to measure the installed depth, and re-install it to that depth. Fine particles can make their way into the pump. 99% of the time this junk will accumulate in the groove on the side of the pump. Clean it with brake clean, blow out the oil lines, and clean out the oil tank. It should be good to go then. Another common problem with the 018 and 180 is that the oil line will become old and allow air to be sucked in where it plugs into the bottom of the pump channel. It won't leak oil, but it will leak air enough that the pump can't prime. Replacement of the line will solve that issue.