Jim Grant's Tech Tips
GMC Pick-up, High Oil Pressure
Q: I have an '89 GMC pickup
with a 305, it's showing very high oil pressure readings. What could be
vehicles of that age are notorious for erratic oil pressure gauge readings.
It's most likely that your vehicle has a defective oil pressure sending
unit. But, it's never safe to assume. A mechanical type oil pressure gauge
should be temporarily installed to check the true oil pressure. The mechanical
gauge will probably not agree with the gauge on your dash. The fix will
be a replacement oil pressure sending unit on the engine.