Effects of Stuck Oil Pump Relief Valve

[CWizard]

Could some of you engine experts please check out my understanding of the effects of a stuck oil pump relief valve :
1. A relief valve stuck in the fully closed position may result in very high oil pressure.
2. A relief valve stuck in the fully open position will result in little or no oil pressure, since the pump flow is dumped immediately back to the sump.
3. Now the most interesting one: A relief valve that is stuck in an intermediate position that blocks part of the relief port can result in reduced, but still acceptable oil pressure. In this scenario, the partially open port acts like a small leak, but the pump is able to handle that "leak" and still supply adequate oil to the bearings, etc.
Right, wrong, somewhere in between? Thanks.
Jerry aka CWizard

[mylesdw]

I reckon the partially open case would result in very low oil pressure at low revs but at a certain rpm the pressure would recover and look more normal. It would really depend how 'open' it was.

[Rick Parker]

If there was a piece of foreign material blocking it, or if the bypass valve is shimmed too much, thus preventing the bypass plunger from opening, the consequence would be unlimited high end pressure. It can reach the point of potentially popping the crimped seal on even a High Performance oil filter such as FL-1HP. I have had this happen, it's exciting and makes a BIG mess. POW!
However too answer your question, YES you would have pressue but it would be very unstable even though the gauge may indicate otherwise. It is like a huge internal leak. It may also tend to aireate the oil considerably. Fix it.