20K engine lube system

[Len]

A couple years ago I bought a "restored" 20k (non running). Today I started it, sounds good but has no oil pressure. Pulled oil guage line at "T" at rear of engine, confirming gauge. When I brought it home, I drained oil, pulled  pan access cover and cleaned as well as I could. Filled with fresh oil.  Oil now sure doesn't  look like new, is it just being stirred by crankshaft or is it being pumped?
Is first step to pull pan? What is most likely problem?
From searching, I know that some people on this board have worked on these engines and understand them.  Input would be appreciated.  
Thanks,
len

[Bob]

I had an AG that wouldn't pick up any oil. The pump must have been worn enough that it was dry and wouldn't prime. I think I could have pumped a little oil in the T and it might have picked it up. I pulled the pan and messed with it. don't know what I did for sure but it worked when I hooked it to the drill...

[Len]

Thanks Bob.  I'll be pulling it into my shop to see what I can find, but it may be a while before I have time.  
I also have an E, one of the very first AG (unstyled), and an early styled AG all of which use the Hercules engine, so am less familiar with the 20-K engine.

[Len]

Well today was a little discouaraging. I pulled the pan, which let me figure out that the oil pump is up high on the outside between the rear of the block and the flywheel. To remove the oil pump, it looks like the enginge needs to be pulled so that the flywheel can be removed.  
Up so high, I imagine that a worn pump loses it's prime pretty easily.

[Len]

I cleaned out pan and reinstalled it. Filled with fresh 40 wt oil. Installed an additional "T" where oil gauge connects (for easy priming now and if necessary in the future)  and forced oil in. Started and had immediate oil pressure which slowly went over 35 psi.
Restarted  the next day and it developed oil pressure. It does have a mild knock (not a sharp rattle like a loose rod, more like piston slap), but I'm not going to worry about that, at least for now.

[clueless]

Be careful with that engine if it's the 4x51/2 OHV cast en bloc in a 1920-27 or so model. I've got a note from 2003 (OMG, how time flies!!) that a smokstak comment said that engine may be a Weidley or a Weidley design m'f'd by or for Cletrac.
Some parts catalogs seem to imply an engine change after eng # K19410 to "own" engine (probably a Wisconsin). Either one would probably be awkward to find parts for. Good luck.