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No oil pressure after car sits for a long time

So I have a RB25 neo engine that sat and didn't run for years. First time I tried to turn it over I could not get the oil pressure light to turn off after cranking it for along time repeatedly with the crank angle sensor unplugged. The oil pressure switch turned out to be working fine after putting an oil pressure gauge on it while trying to crank the engine and there was absolutely zero oil pressure.  Managed to get a hold of an accumsump and push oil through the engine which ended up solving the problem.The engine now has pressure, took the accusump off cranks and runs fine with oil pressure.

Ran and drove the car for a few weeks no problems than it sat again for a few months and now back to no oil pressure while cranking the engine with the cas off.

Has anyone heard of this problem before? Seems like there has to be some leak between the pump the pick up. I also have quite alot of oil pressure on idle from what I could remember 80 - 90 psi.

Or there's dirty lumps of sludge in there that you moved when you pressurised it with the Accusump and they have found their way back to cause you a problem.  Could be the inlet of the oil pump, or more a major gallery in the outlet area.

Probably worth doing a drop and refill with diesel, pressurise with diesel with the Accusump type of exercise to see if you can clean it out.

It could be something as silly as a lump of silicone/sealant hanging out of a flanged joint into the flow.  Like where the pickup bolts on.  Given that you seem to have silly high oil pressure at idle, you may have some sort of aftermarket pump/gears in there, which implies the opportunity for someone to have made a mess with sealant.

It has a nitto pump. I didnt have access to an accusump this time so I just gravity fed with a big funnel oil through the turbo oil feed and it managed to do the trick and the oil light turned off after cranking it over pretty quickly. Sounds like the oil pump is draining completely dry maybe?

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