Packard V12
This pump came in with a note that it had not pumped fuel in many years. After rebuilding it I noticed that the arm was being restricted for some reason. After close to two hours of measuring, and checking casting numbers to make sure nothing was incorrect, the problem was found. During the last rebuild many years ago, a .040 piece of the arm return spring had broken off and was stuck in the seat area. This tiny, 40 thousands piece of spring, was equal to 1" of arm movement. That was enough to keep this pump from drawing any fuel. It only took a piece of spring, the thickness of a paper clip, to make the customer have to go searching for a replacement, and these pumps aren't cheap to replace. It's all set now, I win.