I'm not sure if this will help but when I put my Robarts in I had the same problem except I was using a power pump. Even then I would still only have about 40 psi. After much troubleshooting I found that the Robart filler was too long so when I would screw on the other end attached to my pump it was not depressing the needle all the way causing about 25% of the air pumped, into the system. I ground off about 1/4 of an inch of threads and it worked flawlessly.

Just an Idea, SVX