I'm trying to find where this wire comes out of the harness on my car - an 84 L69 Trans Am with an 80 psi gauge.... that doesn't work. No ECM.

I tested the wire where it goes into the firewall by poking a pin into it and grounding out the pin. This caused the gauge to go to zero. So I know I've got the right wire... but don't know where it goes inside the engine compartment. It dissappears into the harness that runs behind the engine.

I don't see any sending units by the oil filter or distributor, which I believe are the usual locations.

I did find one sensor close to the starter. It had one connector but no wire going into it. But I thought it might be the knock sensor or oil temp switch.

Where does the brown wire go? Why can't I find the sending unit?

 

The oil pressure sensor (OPS) needs to tap into the oil gallery. On a factory SBC, there are two places:

1. top, rear of the block. Also called the "china wall". Just to the driver's side of the distributor.
2. Just above the oil filter.

My 87 L98 OPS is at location #1.

Here is the oil pressure sender (OPS) I expect you have.


This post, has this picture. The red circle is location #2. I think you have the cylinder poking out of the spark plug wires next to the distributor.



Although this is an LT1, that should give you an idea of the location.

Location #2: Found the below picture here... right OPS, not in the location I would expect to find it. (FYI: This Jeep swap has the knock sensor screwed into the "wrong" side (driver) of the block than a Camaro (passenger)).

 

Thanks, those are really great photos.

I checked, rechecked, and had my father-in-law check, and we don't see sensors in either location. The port above the oil filter housing is capped off with an allen screw. I'm sure the engine was rebuilt at some point so perhaps they capped off both ports?

I sure wish I could follow that brown wire to wherever it goes.... I think it would give some helpful clues. But I don't see any way of tracing it that doesn't involve removing the plastic conduit.

 

Thanks. I have some good Google-fu going on at the moment.

I am still assuming the sensor should (have been) next to the distributor. Look for the one loose wire, not connected to anything. It is a round rubber connector.

Say thank to the Monte Carlo guys for this image:

 

This is the factory OPS that I pulled from a 84 Trans Am 'HO' last week.



It was mounted on the rear "china wall" at the end of a long brass fitting with a 90 degree bend. The plug is 'hidden' by the plastic cover shown in the pic. the cover has a couple plastic tabs that lock it to the sensor....... push in the tabs to allow it to be opened and removed to expose the plug.