Hey guys, im getting ready to swap my TBI over to carb. i plan on pulling the computer and harness out, but i am not sure what i will need to re-wire afterwards. i see the alternator and fans are routed through the harness, and i am pretty sure i heard that the fuel pump and ignition are routed through it, too. can i cut the cover off the harness and liberate those circuits from the harness? or do i need to rewire everything? and how much rewiring will i need to do? i have all of the parts for the swap, just not sure about the electrical issues i will have while doing it.

Thanks
Andrew

 

Not 100% sure on the 1989, but the 1990 and later TBI cars when swapped to carb the entire pass side harness can be removed. The driver side needs to remain in tact (there's a few minor things I think can be cut out - but not worth the effort).

Having said that, I chose to leave mine in - it tucks into the fenderwell easily out of sight, and it allowed me to 'make sure' before I went hacking wires. Also, now that I've been finished for 3+ years, it's still there - it gives me a virtually unlimited number of wires already running from inside to outside, that I use all the time for things like adding fog lights, manual fan control switches, lighting, manual torque converter lockup switch, etc. Everyone wants to hack it out first thing - then a month later they have to rerun a wire back through the firewall for something = wasted efforts! Just stuff it into the fenderwell, and save it for a rainy day - you never know when it would be handy to have a wire that's already plumbed through the firewall!

 

I understand keeping it, but i wanted to pull it to sell it with the computer and the rest of my TBI stuff. it'd make it a lot easier for someone else. do you have any idea how much of the stuff actually goes through the computer? or if it's just routed through the harness. i'm sure the alternator doesnt run through the ECU, but what about the fuel pump and starter circuit?

 

If you can, get the chiltons total car care manual for the camaro/firebird. Those have complete reprints of the f-body wiring diagram manual. I used it when I replaced my entire engine harness when I converted over to SFI.

As for the wire harness, it can be removed more or less intact. There will be some things that you will need to pull out, but its not a lot. I dont know about all the years, but the only thing that will be controlled by the ECM that you will need will be the fuel pump and torque converter. There is, however, a switch built into the oil pressure sender that will turn the pump on automatically when the engine builds up oil pressure. With a carb, you should have enough fuel in the bowl for the engine to start up and build enough oil pressure to close the switch and turn on the fuel pump. AS for the torque converter, you will need to get a lockup kit to allow the TC to lock at highway speeds. The 700-R4 will overheat if the TCC is left unlocked at high speeds.

 

i got a haynes manual on ebay for $5.... little did i know it wouldnt have the '89 TBI harness in it. guess i'll keep a look out for a chiltons.

so i'm guessing that the alternator and fans can be pulled out of the harness? i was just going to put the TCC and fuel pump on a set of switches where the ash tray is. i just want to do the swap right. nice and clean the firs time.

 

the haynes manual went through a bunch of revisions over the years; i had 3 different ones to just get all the wiring info i needed. chilton should have the harness info though.

and the passenger side harness (ecu related) should be completely removable without having to cut anything

 

i know you can pull the whole thing, but the alternator and fans electronics go through the wiring harness, and i dont really want to rewire those if i dont have to.

 

https://www.thirdgen.org/forums/ltx-...p-3rd-gen.html

All the info you need.