Frmo what ive read, its from 86 and on.
The gauge is not a 'full sweep' gauge. It is an 'on/off' sender that triggers the gauge to read at 0 when your pressure drops below 6psi. There is a 6ohm resistor somewhere inline to the gauge (either under the hood, or behind the dash depending on year) that helps fool the gauge.
My gauge reads 0psi all the time now, but i know i have good pressure, cause i installed an aftermarket gauge from Autometer.
There is a possibility that your screen is plugged, but i assure you, it is a MAJOR PITA to check that. What i would do first is change the oil and filter (if you havent already since the flush). Not Fram! Then id try getting a new sending unit. IIRC, they are pretty cheap. Then i would go out and get a full sweep gauge and install it.
Then, if your pressure still reads low, you can pull the pan. But i assure you, you do NOT want to do that if you dont have to!
