I bought a Ridgid 535 pipe threader at an auction at an advantageous
price.

This thing did not work at all, at first. Nothing would run. I swapped
the top and bottom brushes and it started to run fine. (because the
bottom brush was more worn, so I wanted gravity to help it). For the
future, I ordered a set of brushes to replace the worn ones.

As of now, the threader runs, but nothing comes out of what I think is
the oiler pipe. I must admit that I am quite ignorant as to how the
oiling system works.

What I know is that

1) Oil is pumped by a gear pump, which does engage with the main gear.
2) Oil pan is relatively full of oil
3) There is A LOT of crud on the bottom of oil pan
4) If I loosen the compression fitting nut on what looks like the
output of the gear pump,no fluid seems to come out of the loosened
threads.

My guess is that the input (and perhaps output side too) of the pump
is plugged.

What else could be wrong?

i