Primary air tank won't build air

[iRonin]

Fill up a spray bottle with soapy water and go spray all fittings, plugs/drain plugs around your primary tank. You might have big leak somewhere there, cause as you said your 2nd tank keeps 120 psi. Find quiet place, Build the pressure as much as possible shut ur engine, go outside spray and listen. You'll find it... Go by an air lines comming out of ur primary tank if nothing found at the tank. Spray them all the way to next fittings. Sounds like it leaks badly.

The oily spot under compressor has nothing to do with compressor. If you check more thoroughly, you find this oil comes from the top part of front gear cover. Might be leaky front camshaft seal, I suppose. Don't know exactly. Rawze, Gearhead or Uni can say what it is for sure. I have the same oily spot last 100K miles and it doesn't go any more. But my engine has 800K on it already.