How hard is it to understand that turning an oil pump backwards will draw the oil out of the engine through the pump and to the oil pump pickup/sump?
When an engine is sitting you have gravity working on the oil but, you have to have a path for it to move down and out of the engine.
That path is measured in the thousandths of an inch of whatever clearance you have in your positive displacement oil pump.
The flow rate is so low that I routinely start cars that have been sitting for 4 years and only the valves that were open had lifters bled down meaning only two valves clicking until oil can pump the lifters back up and remove the clearance.
Unlike leaving a car sitting for a long period and possibly having oil drainback, turning the engine backwards uses suction to draw the oil out of where it would normally not leave.
So a car placed in a forward gear on a hill with Ebrake not properly applied will slowly roll down the hill depending on how steep it is and what gear the car is in.
I made the mistake of 3rd gear instead of 1st or reverse so the car rolled about 1.5 lengths down in an hour before I came back.
In my case, I had all lifters clacking as if they had zero oil in them for a period you might see when running a new engine for the first time.
Remember that the oil leaving these devices end up being pushed around a bearing or the tip of a lifter in normal operation so............turning the engine backwards now makes any "oil exit" a perfect "entrance" for air to enter.
I have already witnessed it as described above and the physics is quite basic.
Turned backwards at the right speed, you can generate quite a few inches of vacuum (mercury) which will pull oil from wherever it is until one route of air entry empties and increases in flow rate causing the rest of the entry points to nearly stop..
That short amount of time is more than enough for oil to be sucked from the lifters since it only has to travel about 5/16 inch before the lifters are empty.
I do turn engines backward but only to "prime" the oil pump when it is impossible to do it with a tool and then only on engines that don't have a device that would be damaged by reverse rotation or may skip a belt tooth since the tensioner is not pumped up yet..
I hook a clear plastic hose to a long and skinny funnel and run it to the port that supplies the oil filter boss.
This port goes directly to the oil pump.
I fill the funnel with oil and turn the engine backwards and watch as the oil is quickly sucked down through the tube and into the port which leads to the oil pump.
I pump at least a quart to ensure the oil has gone all the way down to the oil pickup.
Now I know that the oil pump is full, and that the gallery leading away from it has a nice column as well so I fill up the filter as much as possible and crank the engine.
It's the same mechanism as what empties an engine except I am using it for the opposite by supplying oil from where the reverse rotated engine would seek air.
I get oil pressure immediately at the pressure sender port so I screw it in and undo the oil supply line to the turbo and crank until it comes out there.
Then I enable ignition/injection and start the engine.
Is it possible that your lifetime as a mechanical engineer never brought you to this exact condition.
I've got plenty of gaps in my mechanical engineering knowledge but my engine knowledge has me working directly in this area my entire lifetime.
Ask me about other things and you may find a hole............but not here.
If you think my answer was harsh, it's simply tit for tat replying to a BS post of "pure bullocks" which had zero scientific merit.
I'm the guy on the right asking "why did you guys run 30 pounds of boost to it without filling the methanol tank?"
