low oil pressure

have a 92 s-10 with the 4.3 vortec. oil is full but have low oil pressure on the gauge, which i got the digital dash out of a different blazer and the rpm gauge doesnt really work all the time either , could this just be a problem with the used digital gauges or what and ideas?

have a 92 s-10 with the 4.3 vortec. oil is full but have low oil pressure on the gauge, which i got the digital dash out of a different blazer and the rpm gauge doesnt really work all the time either , could this just be a problem with the used digital gauges or what and ideas?
Right off the bat I would say your problem is the digital dash, but it could be worse. I am thinking it is the dash and something is not connected properly

Maybe a bad oil pressure sending unit? Very common problem on these trucks.

If you had low pressure the engine would knock.

Yep, extremely low pressure would not allow the lifters to operate properly, and self-adjust lash out of themselves. This makes a *terrible* racket. I would go with Dino55 and BLT on this one. The sending unit is not expensive, but it is a pain in the butt to get swapped out. If and when you swap it, run three turns of teflon tape around the threads. I also would check to make sure that the harness was in good shape that plugs into the back of that sensor, as a high resistance connection could show lower than average pressures.

Different years of digital dashes, have different pin-outs, or connections at the back, I am not sure of the year to year differences, but there is differences.