Posted by Andy Maloney on May 08, 1999 at 08:53:57:
Can't figure out why your L6 has no oil pressure after sitting for years? Maybe the oil pump is not able to develop enough suction to draw oil from the pan. Pouring a little oil down to the pump from the oil pressure sending unit line to help prime it might fix the situation.
My 230 had no oil pressure after sitting for years (The guy I got it from I trust. He said it had good pressure ~2 years ago). I verified that the oil gauge worked by shorting it and finding power at the oil presure sending unit. Next I verified that the unit was grounded. No oil was being pumped out of line going to the oil pressure sender from the oil pump when the engine was spin. The oil pan had oil in it. I wondered if the oil pump pick-up or oil galley(s) were clogged.
Out of frustration, I poured oil down the oil sender oil line to see what happened. It bubbled alot going down. Then I spun the engine by hand and heard the oil pump making slurping noises. I poured more oil down the line. After the bubles stopped, I spun the engine 1.5 turns and oil pumped out the line. I re-assembled the oil sending unt and wiring. Next I pulled the cover off the oil filter canisted and Oil was now being pumped to it.
Conclusion: Because the engine sat for years, the oil pump might not be able to pull the initial oil from the pan. Why? I am not sure. Likely there was sludge somewhere in the system and adding the oil down the pipe gave the oil pump something to move which made the suction to draw from the oil pan stronger.(extra oil changes are planned to remove the sludge). The oil gauge now reads 10psi when I spin the engine by hand. Hopefully I'll have time to start it this weekend. The oil gauge stills shows approx 10psi days later when I spin the engine by hand - so I won't have to repeat pouring oil down to the oil pump to get psi.
I hope my experience helps someone avoid needlessly replacing his/her oil pump or oil pump pick-up assembly.