I have an Idea...sorry to sound blunt, but you may want to start looking for a new or rebuilt short block. Good time for a H/C/I upgrade eh??. And while your at it get a real oil pressure gauge on there..stocker is a joke, as I have found out.
Fixing a knock caused by low oil pressure is a serious issue..not something you can ignore. My approach would be to put a real gauge on the car, and if really is low the engine will have to be opened up. Sorry for the bad news..
Don't know..you have to find out the "true" oil pressure situation..if it's low then you need to address the problem. You stated your pressure is almost nil on the gauge, and that you have a knock. Those two combined are not good issues..you can't guess, you need to know the facts of what's really going on.
just cuz u have oil doesnt mean the engines ok... get a mechanical gauge, somehow.. and hook it up to where the oil sending unit is....
if you're running with low oil pressure and you hear a knock, chances are you threw a rod bearing.. which means rolling in new bearings, or worse, depending on how loww ur pressure is and how long you've ran with it that low.
could cost you new crankshaft, new rods, who knows...
DONT start your engine again until u get a mechanical oil pressure gauge on it, pressure should be around 45-60psi at 2000rpm, if any lower than 40, my suggestion is pulling the engine and checking out your bottom end
i too am sorry for the bad news but low oil pressure is no joke
if you're lucky, it could be a lifter not getting enough oil to it, which probably didnt cause any damage to anything... yet, but as stated, dont run your engine, unless you've got major $$$ to put into all new internals
the parts store should have mech oil pressure gauges for around 10 bucks. Money well spent. I agree about getting one and trying it before you drive the car again.
We are not trying to get you to spend money, but 10 bucks could save you a lot more in rebuild costs.