Like most of you here, my oil pressure stopped reading and is pegged at the bottom. This happened about 100k ago but its time to fix it. Where to start on this? Is it the actual gauge in the inst cluster or is it the sending unit? I have a few j/y clusters kicking around but it'd probably just happen again in time. I do not want an aftermarket gauge set up. Thanks for any input!
Roger

 

Pull the wire off the sending unit and ground it. The gauge should peg HIGH.
If not you have either a wiring or gauge issue.

If it does peg, then your sending unit is bad

 

^^^ What he said, with one caveat... If you have actual low oil pressure, the "gauge" will just stay pegged on "L". But even on worn out engines, they'll typically show some pressure when cold. If it was on "L" right from cold start-up, the engine would be near death and sound like it.

Lastly, realize that the "gauge" is not really a gauge at all. It's an "idiot light" masquerading as a gauge.