I pulled the stock 305 TPi out of my 91 Z the other day, and in taking apart everything under the hood, i ran into a MESS of a wiring harness. I am trying to swap out the TPI for a bigger carb motor, but i was wondering if there was anyone out there that knew of any aftermarket co. that makes a wiring harness that makes this process easier. (i was told to look on Painless wiring, but they mainly do harnesses for carb to EFI swaps) Could anyone point me in the right direction to find a replacement harness so that i dont have to sort through each and every one of these wires in the harness and pull out what i dont need. thanks

 

Did you mark what you disconnected? For a carb, you're going to need ignition power (went to the coil) and tach feed (also went to the coil), the alternator wires, coolant temp for the gage (went to the head), oil pressure, and that's about it. The harness that goes to the passenger side fenderwell is the ECM harness, and you aren't going to need those wires anymore.

 

So basically what your saying is that there is no repalcement harness i can buy and plug into the fuse box (replacing the old TPI harness) to run a carb set up. I have to go through each wire and find its purpose?

 

get a wiring schematic & track them down. ALso, teh harness should be curved/bent in a fashion to where you can guess where it was going.

 

You are correct.

I don't know if you can get away with using one from an '82-85 model harness from a carb car, there will still be a bunch of wires you will have to sort through to find the ones you really need, but it would be closer than sorting through the TPI harness.

Plus uncut TPI harness' are hard to find these days.

 

MentalyDeranged,
If you do find a harness from a carbed vehicle be aware that the wire mapping will almost certainly be quite different on the INTERIOR side of the firewall.

My son and I converted his Z-28 from TBI (Crossfire) to Carb. We replaced the harness within the engine compartment with one from a Carb vehicle and "Plugged it in" to the firewall connector. Almost nothing worked and what did work worked incorrectly. We also had to remove the dash and replace the "Interior Harness", Fuse Panel and several accessories from a Carb Donor. Finally.... everything works.

MAJOR PITA... Been there.....done that!!!

Kurt

 

So all the wires that run though the passanger side of the firewall/car are for the ECM?

 

That is correct.

 

yea, i figured it would be as easy a replacing it. well i spent most of last night in my driveway trying to UNTANGLE the wiring harness disaster.
but i am by no means finished. i do still have a few (possibly stupid) questions. ok here we go,
1 there were thre plugs the plugged into a plastic piece on the firewall, a friend told me that they were for the relays. is all that needed? or can those be removed too?
2. there was a wire that went to the starter,but when you trace the wire back one way, it changes color from red (or dark orange) to green(i think) and then goes to a plug or two, and then proceeds to the passenger side fender where the computer is. are those wires need? i was assuming that they were for the ignition, but i am putting a 6A box in. so if they were for the ign i wouldnt need them.

 

Mentaly Deranged,
There are several different items mounted to the firewall on the Driver's Side. Depending on what your original car was equipped with you could need some of that stuff.... Here are some of the things (Relays, Etc.) that COULD be mounted on the firewall at the Driver's Side. A/C Relay, Fuel Pump Relay, Map Sensor, Knock/Spark Control, Cooling Fan Relay (often that relay is mounted next to the battery). If your keeping A/C and the original Electric Fuel Pump you'll want to keep those.....

Got any photos of the wire(s) in Question #2? As Five7 mentioned anything that goes down under the PASS SIDE Fender is ECM related.

ADDITIONAL INFO:
There are several "DISTINCT" harness segments.....
#1 - Huge strand Pass Side / ECM
#2 - Large Strand Driver Side Plug to Fire Wall - General Engine controls Distributor, Coolant/Temp Sensors, Starter, Alternator, etc.
#3 - Small Strand (next to #2) Forward Lighting
#4 - Small Strand Heater & A/C Enters Engine Compartment Behind Cyl. #8
#5 - Very Small Strand - Cruise Control - Runs along Frame Rail on Dr. Side.

Sincerely,
Kurt

 

Guys, thanks for all the help. But one more question. I am working on the car right now, and i followed all the wiring in the pas side fender. all of the wiring that went inside the car plugs straight into the computer. HOWEVER. there are 12 wires that come out of the computer and go into a plug, once into that plug, they run up and under the dash and i cannot see where they go. My assumption is that they are the wires from the ecu to the dash for the idiot lights, and due to the fact that i am running gauges and what not, they are unnessicary. am i wrong? also, there is this white wire that is slightly thicker that all the rest. It looks like it was soddered on to one of the injector wires that went into the computer. would anyone be able to tell me what that is?