[blichjr]

I FINALLY figured out what was causing my excessive smoking issue on my 89 930. It would literally blow gobs of oil out of the exhaust on cold start. I would estimate 3-4 oz easily. Massive smoke screen for 15 min until it all burned out of the exhaust. Gobs of oil in the intake system as well. Disassembled the turbo scavenge pump and all seemed normal - no excessive wear. Replaced the seals for good measure. During an experiment like Steve did above everything seemed normal. Engine off.
Went in the house to grab a sandwich and when I came back out the bucket was filled with about 20 oz of oil! Note: I'm using stock turbo oil tank.

I repeated the test and verified that it did it again. Repeated again and this time I used a vise grip to pinch off the turbo scavenge pump return hose where it goes back into bottom of the remote oil tank (immediately after I turned the engine off). The bucket did NOT fill this time. Repeated a couple more times each way and that was definitely the issue. The static oil pressure from the oil tank was pushing oil backwards through the oil pump and overfilling the turbo drain tank over a period of several days. All the oil backed up through the turbo bearings and into the exhaust and intake sides. When the engine fired up all this oil would blow into the exhaust and intake system.

Fix was simple - I ordered a check valve from McMaster.com (couldn't find one on Pelican unfortunately) and installed it in the hose going from the turbo scavenge pump outlet into the bottom of the remote oil tank. Be mindful of the direction - the flow arrow needs to point to the oil tank, not the pump. Problem fixed! It took several runs to get all the oil burned out of the exhaust and sucked out of the intake.

Hope this helps!

John