Forum » General Engine Building Discussion » Seem to be losing oil prime in fresh engine. Nissan RB26

Seem to be losing oil prime in fresh engine. Nissan RB26

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I recently assembled an RB26 and I notice if the engine sits a few hours or overnight it will take a full 2-3 seconds after starting to build pressure. This seems excessive to me as if the prime in the pickup is being lost. Usually I expect about less than 1 second for pressure to build.

This is fairly typical as far as I can tell. It's not the pump loosing prime, it's the oil passages draining. It takes many revolutions of the oil pump to fill all those passages before the oil pressure will register.

That's one reason we usually crank our race engines over until oil pressure builds before turning on the ignition.

Google "Engine Pre-oilers" and see some of the solutions various folks offer. Race cars, airplanes, boats and other engines that may sit for long periods of time between running often use pre-oilers to keep the startup scuffing in check.

Thanks. I'm familiar with accusump and similar devices. I was hoping not to fit one as this is a street car and retains the stock location oiling components. You know when you change the oil filter and the pressure light takes a few extra seconds to go out if you just start the engine rather than prime it by cranking. Thats how it acts on any cold restart, even within a few hrs. I verified with a gauge that the light is responding properly. maybe I'm overthinking it but every other car I've ever driven doesnt seem to take that long.

Maybe a problem with the anti drain valve in the oil filter?

Yea im going to do some testing on the filter housing try a nissan filter and see if anything happens. I might try eliminating the housing/cooler completely and see if that get it anywhere.

Looks like the oil filter did it. 2 Wix filters in a row problem still there. Then switch to a Nissan filter and the problem was solved less than 1 sec for pressure. Thanks

Not sure if oil was actually draining back or the valve was just a little stiffer in the Wix filter. I never ran into that before.

Awesome, glad you found the problem.