Low oil pressure cause

To check the hoses, I have unplugged the hoses:

- from oil tank to radiator-in

- from radiator-out to oil pump

- from under the crank case to to oil tank

and then, made sure there was no obstruction (by adding some air pressure) and no evident air leak building a bit pressure in them.

I wanted to purge the oil system after this, by:

- reattaching every hose

- adding new oil in the tank

- cranking with mags off and plugs OUT

But it seemed like no oil would get sucked in the crank case... so I tried connecting a hose straight to the oil pump, with a funnel attached and placed above the engine. Cranking for a few seconds (approx 5 seconds) would not make the level move at all.

I have also check that the pump does rotate along with the crank shaft, so I am confused and don't understand why oil wouldn't get IN the case. 

I really appreciate your help!

Something strange I had also noted before troubleshooting the low pressure issue, is that when I checked the oil level in pre-flight inspection, I could hear the "oil burp" in the tank after pulling the 1 or 2 blades, as if the return hose would only eject air.

You have no Oil because you did Not follow the "Purging " Procedure in the Installation Manual.

Section 79-00-00, Chapter. 3.3, Pages 23,24 and 25.

- - -

Yes, Mostly Air and Lots of it are returned to the Oil Tank, that's why it is called "Burping".

There will be more Air than Oil.  The Air is what pushes the Oil.

I tried the procedure as per the manual, but hardly any oil would get into the crank-case.

May I please ask you the following questions to clarify some doubts I have?

1) If I connect a hose to the hole identified in pink in the picture attached, and injected oil in it, would it need pressure to get inside the crank-case or would it flow in with gravity? Is it possible that this hole could be clogged, not letting any oil get in?

2) Before I started all the checks related to this topic, when I checked the oil level between two flights on two different days it would only take 1 blade to hear the burp: would that mean that there was no oil in the engine? 

3) Do you think a low oil pressure (1.6 bars with engine running) could be caused by a faulty part inside the crank case? 

4) Can a clogged oil filter be the cause of the low oil pressure?

Thank you!

Bill, a fifth question as I tried the purging following the installation manual:

5) I disconnected the oil return line and let it hang over a bucket, pressurized with 0.5-1 bar the can through the vent line, but only a few drops of oil came out of the return line after nearly 1 minute. Given my previous questions, could it be that no oil actually gets into the crankcase? I noticed that the pressurized oil can would keep the pressure as if the level of oil stayed the same in the can.

Thank you for your help.