Hello,
I just need to know which wires are for the fuel pump itself and which are for the fuel level gauge on an 85 tpi motor from an iroc. The harness from the tank has 3 wires: purple, dark gray, and light gray. We are swapping an 85 tpi into a 84 trans am. The trans am has only a pink wire and a black wire on the harness for the fuel gauge because of the mechanical pump. We need to run a wire to the fuel pump relay up front, but which one to I hook it to on the tank. Thanks.
John

 

On my '87 IROC, the fuel pump power wire is tan.

 

Thanks for the reply. If I'm not mistaken, 85 tpi is completely different than 87-89, and 90-92. I alreafy found the diagram for the 87-89 pump with the tan power wire. for some reason both of my manuals don't have this info for the 85, or I can't find it. anyone ever looked at the wiring for an 85? this pump has been replaced once also, so it may not be in any wiring diagrams. is there anyway to tell by looking at it?
Thanks guys,
John

 

Well, GM really never changes colors of any wires in the cars throughout the years. Like 4th gens still use the same color wires in their cars, cuz it's much easier to keep track of through the years. Lemme run a situation by ya. I've been working on thirdgens a LONG time. I've found that any wires exposed to the weather or air outside turn colors. Tan loves to turn white and gray. White loves to turn yellowish/tan. So sometimes you really gotta clean the wire itself really well to see it's true color, and sometimes the wire just changed color to a point where you'll never know what color it was originally. You can check by tracing the wires to a place where it's not exposed to the weather, and then you'll probably see the true color of the wire.

BTW, the '85-'86 and the '87-'89 TPI's were only different because they went to a new style intake manifold. Nothing with the fuel pump wiring was changed between the '83-'92 years.

 

Hehe heh.......just did this............only went the other way.
my '87 TPI had black, tan and purple (or pink) depending on your whether you look in the car or out.(it was purple on the fuel tank harness.....pink in the connector on the body.

Black=ground to fuel tank
tan=power supply for fuel pump
purple=fuel level sender to the fuel gauge

When I swapped in the earlier sening unit w/o a pump, it only had 2 wires (similar to the Trans Am one you describe)

black=ground
pink=fuel level sender


The power to the electric pump is the TAN or the lighter gray (the one you say is dark gray should actually be the ground). The Trans Am does not have the power wire....you will need to run it.

Also the wires have changed..........but its mainly in the differences amongst the different sending units.

 

Thanks guys! That helped us out a lot.
sincerely,
John