Low oil pressure?

Jadaharabi said

If that plug is not in there and the engine is pumping oil then let's say for example the oil pressure gets up to 60 pounds. The bypass in the pump opens and drops the pressure in the pump so then by not having the plug in that line the oil goes back to the filter and it stops going up to the top of the motor then pressure drops bypass kicks out oil pressure builds up again feeds the top of the motor. Until pressure builds up bypass opens in the pump and once again the oil pressure drops.

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The restrictions that cause pressure buildup are >95% in the motor and do not change with the filter bypassed. So, there is always positive pressure from the pump on both the passages to and from the filter, with or without the plug. The oil cannot 'stop going to the top' of the motor since there never is any lower pressure in the filter area to which it can flow.

The air in the filter may provide some 'softness' in the pressure regulation until the air bleeds out of the filter; that part I can see. Some oil will want to slowly feed through the filter and will bleed it out any air eventually.