601 no oil pressure.

[dieselnutnj]

I recently finished re assembling a 601 basket case. Went to start said engine and found I am getting no oil pressure at all. Zero on the guage. I looked in the filter housing and it is bone dry. I had pulled the pan down and cleaned all the excess parts out of the pan. (guide rail shattered) I double checked to make sure chain was on oil pump etc. I pulled down the pump, cleaned the sump screen and tried pump in kerosene and it pumped just fine. Does anyone know if this engine goes into bypass mode if the filter and guage stay dry? There is no huge puddle to indicate a leak, just no oil seems to be moving through housing. I'm open to any ideas anyone has.

Rick