Yes.
For sake of illustration, lets makes some assumptions:
1)assume your engine takes 5 quarts of
oil before adding the Accusump.
2)Assume a 3 quart Accusump.
3)Assume you install the Accusump with an initial pressure of 50 psi
4)Assume your engine
oil pressure at 2000 rpm is 50 psi
5)Asume your engine
oil pressure at idle is 30 psi
When you install the Accusump, your engine's oil pan has 5 quarts, and the Accusump has 3 quarts for a total of 8 quarts of oil in the system.
Before starting the engine, the engine oil pressure is zero and the Accusump pressure is 50 psi. Then you open the Accusump valve. Now the Accusump has 0 quarts of oil and your oil pan has 8 quarts of oil (assume that all the oil in the Accusump disharges - most likely in actual operation there is some amount left in the Accusump), the oil pressure in the engine is greater than zero, and the pressure in the Accusump is less than 50 psi.
Now you start the engine. If you rev the engine to 2000 rpm (just for illustration - I'm not saying to do this on a cold engine), the oil pump raises the pressure in the system to 50 psi. The Accusump now re-pressurizes to 50 psi and fills with 3 quarts of oil.
If you now went back to idle, the oil pump is only pressurizing the system to 30 psi, so the Accusump releases oil and increases the pressure in the system. However, this is only temporary - if you stay at idle, the pressure in the system (engine & Accusump) will drop back to 30 psi and there will be less then 3 quarts of oil in the Accusump and more than 5 quarts in the oil pan.
Before shutdown, to re-pressurize the Accusump to 50 psi so you will be able to pre-lube on the next startup, rev the engine to 2000rpm and shut the valve.
Pete