i got a set of two wires routed inside the black plastic loom running in front of my rear seats. the wires are blue and black or white and black i think. 87 firebird.

 

Wires are for intank fuel pump.

 

I see the fuel wires, but these two wires split off and run up the passenger side rocker and back behind the dash.

 

Fuel gauge sender?

 

Passenger side rocker? That does not sound like the fuel tank wires, those go up the driver side. And the color do not match either.
The fuel pump power wire is tan/white and the fuel sender wire is pink or purple.

Where does the other end of the wires go, Crazybird?

 

They go from the passenger side kick panel along the rocker, cross over the "hump" in front of the rear seats. I think from there it goes to the rear of the car. the fuel pump has two wries coming off of it. These are not those two wires.

 

When the wires cross over the hump, do they go directly under the seats or do they continue to the side of the car where they disappear under the plastics of the sail panels?

It would help to know the exact wire color, when you get a chance to verify, thanks.

 

The do go all the way to the plastic. There are a total of 4 wires that are in front of the seats. the black and yellow wires are the ones in question.

 

Black and yellow, gotcha.

Black is normally ground. And yellow is a standard color for the left rear turn signal. Also, some years, GM used it for the third brake light. Though the wires never cross over from the passenger side to the driver side, which is puzzling at this point.

One other possibility is that the wires are aftermarket, let's say for an amp installation in the trunk, alarm etc.

I would definitely probe the yellow wire with a test light and see when there is power to it (while applying brakes, with turn signals on, with key on, with radio on etc). It should help us determine its function.

Let us know what you find.
Lou

 

Its defnately not aftermarket. it is in the black plastic and has factory clips all around connecting to the body. I dont have a test light. I guess I will just start removing plastic and trying to trace its origin.

 

You can get a test light for a few dollars (Harbor Freight often has them on sale for 99c).
Or you can use a voltmeter.