i recently noticed a humming noise coming from the rear of my '96 4 door blazer. the sound is there while running and as well as when its not. like after sitting for 8 hours while at work, the noise is still there. its sounds like its coming from the fuel tank area, but i have no idea what it could be since its turned off, and the keys removed. my oil gauge has also started acting up, while driving it maintains a constant oil measurement, but as soon as i decelerate, it drops off horribly. then as soon as i accelerate it returns to normal, and while idling it measures way low, even after i changed the oil it continues. any ideas?

 

Could be your fuel pump isn't shutting off...it's located in the rear and makes a humming noise...

 

oil gauge normally increases with acceleration as far as the humming i would get your fuel pump checked.

 

As for the oil pressure, what type numbers are we talking about, exactly? It may not be anything to worry about, or it could be either an oil pump going south or the sending unit could be bad.