Hi, My ‘97 ranger has got an oil pressure gauge that keeps moving up and down really fast, or sometimes it just says I have no oil pressure. Does anyone know what this could be?

 

Um that's a problem.
is oil level good?
Is it good oil? Not sludge?
it could be just the sensor in the Fritz
worst case scenario it's the oil pump on the fritz. That could cause catastrophic engine damage. W/o oil engine blocks turn into solid blocks of metal.

 

That’s probably a good idea, it could use a change. I’ll see if that fixes it, thanks.

 

1988 and up Rangers(Fords) use an oil pressure SWITCH, an on/off switch
Oil Pressure above 5psi closes the switch so its ON, which means its grounded to the engine block

In most years its a 1 wire sender/switch, when closed it grounds the gauge in the dash, the gauge has a resistor that will cause the needle to show in the "normal" range
Any fluctuation in the needle would be electrical

The sender/switch is the most likely cause of what you describe, as actual low oil pressure would cause instant valve trail noise, louder "ticking" from engine, which you don't mention

Because these sender/switches need a good ground to the engine do NOT use tape on the threads, make sure some of the threads are bare metal to give a good ground
You can also use a jumper wire to battery negative on the sender wire, then turn on the key and oil gauge should show "normal", have someone move the sender wire around to see if gauge needle changes, indicating a possible wire problem in engine bay, unlikely but can be tested

 

your gauges could be out of calibration.My 96 also shows no oil pressure,but truck runs fine.

 

I had this problem with my 89 STX with the 2.9L engine. The connector on the wire to the sensor had gotten loose. I crimped it a little and reattached. The problem went away.