wiring removal questions

[shocker]

I have a 94 3500 with a 454 and 5 speed. The motor had a fire and melted some wiring so I figure now is the time to make some changes. I want to run a FAST injection system and eliminate the factory TBI setup,if I want to keep all other systems (a/c, gauges, cruise etc) what portions of wiring can I remove without a proble? Do I still need a computer if the motor and tranny wont need one? Thanx for the help

[LynnJr]

I run a 1990 with a carburetor and points type distributor by simply unplugging all the throttle body stuff and taping it up with vinyl tape and laying it alongside the valve cover.

I replaced the HEI with points because I wasn't sure if the HEI would work without the computer.I was thinking it wouldn't get the right signal and retard the timing like it does when it throws an error code.

On the transmission being a 5 speed that is exactly what I have and you need the vehicle speed sensor(VSS)so the speedometer works.

The good thing is all the connections are snap ins so you can try it out and if it doesn't work you can put a new wiring harness in it pretty cheaply.

Get a used one from a wrecker for around $90 and check out all the individual connections before you install it.
You can buy each connection with a pigtail at your local O'Rielly's or Autozone.

[shocker]

I have looked for 2 years for a harness, I cannot find a harness from a 5 speed, I got a 4l60 harness but the computer is different and the connectors to the tranny are all different.

[imjeff]

Take your bulkhead connector apart and eliminate the wires you don't need and run new to what you do need. Just look at the wiring diagram, figure out what you need and start tinkering. It will look a lot cleaner without a bunch of wires taped somewhere.

[shocker]

is there a good thread on a tbi to carb conversion which explains what is and what is not needed electrically? I haven't found any but I am sure one must exist.

[imjeff]

I'm not sure if there is a thread, but if you download the FAST installation instructions to see what it needs, then eliminate everything that goes to components you are eliminating it seems like you'd be in good shape. You should start a thread, snap some pics and see where it goes. Then you'll be the dude that did that thread that someone else used! Kind of a cool deal!

[LynnJr]

Shocker
I didn't do a thread but everything that goes to the TBI unplugs and gets eliminated.You can also eliminate all the electronics on the manifold itself.

I went with a Moroso low profile air cleaner so I needed to stack two air cleaner bases on top of each other so the throttle wouldn't hit the air cleaner.

I was able to use the factory brackets on my new manifold but only after some cutting with a die grinder for clearance issues.

The job isn't really that hard if you retain the factory harness

On the harness itself most wreckers tend to cut them and that is why you are having difficulty getting one.I live in California and the wreckers tend to pull everything apart and sell as much as possible.You might try looking here are in a western state with lots of trucks like Idaho.

[lha1992]

You can eliminate most of the injection wiring stuff like the coolant temp, throttle position, mad an what not that went to the original TBI stuff since the fast EFI Setup will come with all the necessary wiring. Now do keep your VSS wiring going to your tranny.

Also a good site too look at if you can't find the right answers here is GMT400.com or org I can't remember. That site is dedicated to all 88-98 trucks. Hopefully I'm not breaking rules here's saying that sorry just trying to help the OP.

OH an for the poster in this thread that's running points on his originally TBI truck you can go to a big body HEI distributor from a 75 an later non computer controlled car or truck. I switched to a HEI on my 72 an it had points so ditch them points lol.

[shocker]

so the computer stays and you remove the wires you don't need, remove the check engine light and that's pretty much all that's required electrically? sounds like a simple project, all I have to do is repair the fire damaged wires which will be a little more time consuming.

[LynnJr]

Shocker
If the fire didn't burn the whole harness all the way to the firewall block go to a pick u part type wrecker and take the wires you need off of several trucks if you have to.
I figured you burn it down hard but if all you did was burn the engine wires and maybe the hood is mangled beyond repair just get the engine wires.
I would bring some pliers and a couple screwdrivers along with 8mm-16mm open end wrenches and a good pair of dykes plus a sharp knife and a bucket.
Find your year truck and start unplugging connectors working your way back towards the firewall.
If your wiring block at the firewall isn't toast you can use crimp-ons or solder to reconnect the new wires.
The only wires that are kinda hard are the turn signals and marker lights because the connections are big and they are right near the front bumper which always gets smashed on wrecking yard trucks.
If you need those start on the passenger side fender and work your way to the headlight then the horn relay in the middle of the grille.Then go to the drivers side headlight and all is well.
Let me know if you need specific wires and I can check here.

[shocker]

thanks for al the replies. I have a harness from an automatic 350 so I will pull my harness apart and figure out what to eliminate and then see what I need to repair. Nothing a few beers and a weekend cant cure!