I need help. I spent the past year rebuilding the 1995 Blazer Vortec Engine.

Its been back together for months, and I cant use it because it has Low to 0 Oil Pressure at Idle. Oil Pressure climbs to 40 or more when the accelerator is pressed. It also has pressure at idle when cold, but goes to zero within 5 min of driving.

Add to that, yesterday, I got a sudden loss of power. The RPMS seem to go really high when accelerator is pressed and I hit 30mph. I can feel the transmission shifting as it should, it feels like its in the engine.

Re: Oil Pressure.. Im out of ideas. I have already:

1 - Changed Oil Cooler Lines and rubber gaskets
2 - Changed Oil Filter Remote Lines
3 - Changed Filter and Oil to heavier 20w-50, no change in pressure.
4 - Changed O ring and gasket on Remote Oil Filter Adapter on block.
5 - Changed Oil Pan Gasket, but it still has oil leaking from the pan. I cant seem to get it tight enough to stop all oil leaking.
6 - Flushed Oil Pan with Kerosine thru dipstick tube to allow pickup screen to soak in case it somehow got blocked. Drained kerosine next day. Never ran it with kerosine of course.
7 - Oil Pump and Screen were new a year ago during rebuild.
8 - Changed Oil Filter Bypass Valve under filter attachement on block and under actual filter on remote extention.
9 - New Bearings a year ago during rebuild
10 - Changed two new oil pressure sending units.

Im out of ideas and have no idea what to do now with no idle oil pressure, and of course the sudden low power as of yesterday.

Nick

 

The only time I have ever had a problem with no pressure at idle was bad mains and/or bad rod bearings.

 

It is either shot bearings or it could be a bad gauge.

 

Yep, bad main/rod bearing(s) or bad gauge circuit (as mentioned in the 2 posts above). Meanwhile, zero, or near zero, actual oil press at idle would result in some serious bearing knock/rattle IMO. Also keep in mind that some of these vehicles have a 'oil pressure safety' switch that, if operating properly, would shut the eng down if oil P isn't with specs. I could be wrong about this tho. So, if it isn't rattling/knocking then you might consider checking every electrical ground you can find/get at. I've seen some pretty crazy/erratic/inaccurate electrical gauge readings that were chased down to bad ground issues (particularly gnds that are located on the eng). Good luck, and keep us posted!

 

Thanks all. It never occurred to me to check electrical grounds for this. Im not getting incredible knocking or rattling, but it does seem to get a we bit louder when idling with the low pressure. I havent driven much to find out fearing causing damage.

I just changed out the bearings before the rebuild, which makes me wonder why they would be worn, but I could have done something wrong I suppose.

Just before the power loss, I fixed a fuel leak. Maybe the fuel leak was caused by a fuel pump going bad. Its running and not sputtering, but maybe the stream is weak causing the low power, unrelated to the low oil pressure.

 

I forgot to ask you what your idle speed is. It should be ~600 rpm w/ an auto transmission in drive when fully warmed up (most manual transmission equipped vehicles will generally run at a slightly higher idle speed as compared to auto equipped versions).