low oil pressure
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The sending units have a habit of "sooting up" from dirty oil. The nature of a diesel engine. The soot causes the transmitter to not read correctly giving you a low reading and effects the warning light. These old trucks are also subject to electrical resistance problems that can also effect the reading. If you haven't replaced your sender, try that first.
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thanks
chan
#9
Like cougar said, it could be a resistance problem. Does the low oil pressure light come on at an idle when cold and hot? If so it is an electrical issue, beyond the pressure sensor. According to your mech gauges the actual oil pressure is correct. The high resistance in the connectors and wires is giving the PCM a false reading.
#10
Ironically, my truck started this, but it doesn't have the low oil pressure light/buzzer. Can you agree that it's the gauge or wires again? It will drop to the rest, and come back, and drop randomly no rpm shake or movement related. Where would you hook up a mechanical oil press gauge and what is the tech manual specification for low idle and high idle oil pressure?