Not pumping??

Which way is the cupped washer supposed to go? I would assume it is with the cupped side towards the cam so it will grip the eccentric at the outer edge of the cupped washer; looks perhaps like it was run opposite before? If it is in the right way, then it just may be worn down from all the prior spinning, or is bent back. With an added washer, I would put in a hardened washer, not a soft or standard washer, with some 'teeth' raised on the both sides with a chisel, to try keep things from spinning at all. I would be fearing that any movement would eventually cause the key be worn off again eventually. Also, I would put a smaller washer against the cam end to make sure the bolt is torqued against the cam end if the other washer is setting the cupped washer further out.

Can you get a new cupped washer?