Hello and welcome to 2CarPros.
Those pressures could be correct if it has a thicker conventional oil in it. First thing I would do is stick a mechanical gauge on it to see what is really going on.
The fuel pump and oil pressure switch are the same part. The way it works is that you turn on the key, the fuel pump relay kicks on for three seconds to pressurize the system and then shuts off. As soon as the engine starts turning and starts running the oil pressure turns on the fuel pump through the switch. This also functions as a roll over system as the oil pressure will go to zero if the oil moves away from the pump pick-up in the pan.
It also is a way to tell if the relay is bad, you will need to crank the engine a while until the oil pressure trips the pump switch on. It is mounted to the front of the ignition module under the manifold inline with the alternator.
On the diagram the orange wire is battery voltage, The gray wire is power to the pump.
The green wire is the prime signal from the ECM. To run your oil pressure test you need to power the pump as removing the sensor will also stop the pump. This is easy to do, just jumper battery voltage to the Red prime wire or in the pressure switch just jump the orange wire to the gray wire.
Then there is also the oil pressure sending unit that is the other part of the switch. It tells the ECM what the pressure is and the ECM tells the dash what it should display. It uses the Tan wire in the connector combined with the ground it gets through the housing and engine block. There is a variable resistor inside that reacts to oil pressure.
Oil pressure on that engine should be around 55psi at 3000 rpm.
Hope that helps.
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Friday, April 19th, 2019 AT 1:21 PM