So yesterday both the low oil and low pressure light came on,I'd just checked the oil a couple days before but stopped immediately and checked again.Pulled the rocker cover cap and fired it up,good amount of oil spraying around so I drove it slowly back to the house,light goes out and doesn't come back on.
Dropped it off at the import shop and they just called after checking pressures(lights still off),20psi at idle but only rises to 25 psi at 4k rpm-about half of spec.I remember reading about low pressure possibly being caused by failing seals/o-rings in the oil pan,should I count on doing an oil pump with these seals or are the pumps bulletproof?.Other options?.
Its our only set of wheels at the moment so I need to deal with it asap.
Drop the pan and buy the oring kit. Sludge can block the oil pump screen as well.
I would check the PCV system. They clog up pretty bad. One way to tell is have the car idling, pull the dip stick and see if you get any smoke that comes out....
Turbo 850 in my mind is a Volvo, if so then I'd say 95%+ it's the O-ring on the oil pick up tube. However you said you removed the "rocker cover," so it's obviously not a Volvo 850.
Pcv system is all new,no effect on oil pressure anyways though.
The sludge is what I thinking/hoping for as the light hasn't come back on since the initial problem,I plan to do a short duration sea foam tomorrow and do an oil and filter change immediately.I'd like to have the pressure checked again to see if that helped before dropping the pan to do the seals and possibly the pump,is doing the pan seals without doing the pump a dumb idea?.I have no idea on the life span of the volvo oil pump.
Hold on, it is a VOLVO 850? Oh, I see, you just took the cap off. I read that wrong I guess. There was no way you took the upper cam cover off and ran the engine. 
My money is on oil pick up O-rings, most common reason for the low pressure light to come on.
