Installing an Oil Pressure Gauge
To install an oil pressure gauge you will first need to purchase one. These can be purchased from most speed shops or the Grand Prix Net Store. The type of gauge is irrelevant.
Electronic Oil Pressure Gauge Mechanical Oil Pressure Gauge
The port for either mechanical or electrical installation is located about six inches behind the oil filter towards the engine. To find it, remove the passenger side front wheel. You will see the filter. Just behind it is the factory oil pressure switch. It is silver in color with two wires running into the electrical connector.
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This switch only goes to an idiot light on the dash. There is no signal to the PCM. The reason for noting this is that the switch will be permanently removed. If you are scared about not having this light on the dash, think of it this way. You will now be able to see the actual pressure. That switch closes at or below 5 psi of oil pressure. This is lower than you want to be. So the new gauge will be a better solution.
Also, GM decided to use a normally closed switch that opens when the pressure comes up. I was curious as to why GM would do this. If the connector came off or a wire was cut, the light would never come on with the current configuration.
So, after draining the oil, remove the electrical connector off of the pressure switch. Next remove the switch. It is threaded into the housing and comes out fairly easy.
The rest of it is up to you depending on what type of gauge is being used, either mechanical or electrical. I would suggest an electrical since only a single wire needs to be run from the sending unit to the gauge. Whereas the mechanical one would require tubing to be run into the car with the chance of a leak. Warm oil on the carpet inside the cabin is not a good thing.
Either way, the port you will adapt to is a 1/4" pipe or NPT female fitting. If you are using an electrical sending unit, most come with 1/8" pipe threads. You will need to stop by the parts store and get a 1/8" female pipe to 1/4" male pipe fitting. Brass would be fine.
Install your fitting or sending unit, with adapter if needed, and run your signal wire or tubing to the gauge and supply a switched power source for the backlight. Another document is available that describes how to light up your gauges easily so that they dim and light only when the dash lights are on.
Below is a wiring diagram for the Autometer electrical oil pressure gauge:
Questions? Ask Steve Calbert (firstname.lastname@example.org)