no oil pressue, oil has left the building

[shadetreemechanic]

1999 Chevy Blazer is in need of help again! last night my oil pressure dropped to zero. I quickly drove a 1/2 mile home. There was oil under the blazer near rear seal. I crawled under this a.m. but could not tell where it came out. I put some oil back in the motor and cannot see any leaks. but now I have no oil pressure and it appears like the oil is not going anywhere. Could the oil pump be bad? Any suggestions would be very helpful. Thanks

[Cas]

I feel the oil pressure switch is suspect. Do you hear the lifters chattering when the engine is running with no oil pressure? if not the oil pressure switch is probably bad. I assume this is a 4.3 vortec motor, and if so the oil p.s.i. switch is located next to the distributor. Remove it then hook up a manual gauge. Then check to see if you actually have oil pressure or a faulty part.