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nonsensekid20
Member
Joined: 30 Sep 2010
Posts: 490
1991 Chevrolet Camaro RS
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 Posted: Sat Aug 24, 2013 8:39 am Post subject: LS1 Wiring |
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This may be a dumb question but in my searches this is what I've found the least information about. I've followed Alphius and his swap turned out awesome. I've also looked through TGO (Which I would prefer not using too much, as they like to hack things) and some through LS1tech.
My question is, my car used to be TBI and I tore out that harness and kept only what was necessary for the Carb. That harness is in shambles now and unusable. So basically, how am I supposed to wire the LS1 into my factory stuff in order for everything to work properly? Also, I still have the in tank electric pickup around here and will put that back in with the walbro but do I need some other wiring back there or can I use stock fuel pump wiring? Or would I be better off leaving the carb pickup in, and installing an external pump? |
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iansane
Member
Joined: 16 Jan 2004
Posts: 5740
Location: Bothell
1991 Pontiac Trans Am
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| Posted: Sat Aug 24, 2013 8:52 am Post subject: |
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Most of the LS wiring comes from the donor engine or a donor harness that you modify to fit your car.
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| Quote: | | Sometimes I actually think I'm slightly retarded in the mouth. |
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Alphius
Peanut
Joined: 05 Sep 2006
Posts: 2429
Location: Grand Mound
1984 Chevrolet Camaro Z/28
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| Posted: Sat Aug 24, 2013 9:51 am Post subject: |
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| nonsensekid20 wrote: | | My question is, my car used to be TBI and I tore out that harness and kept only what was necessary for the Carb. That harness is in shambles now and unusable. So basically, how am I supposed to wire the LS1 into my factory stuff in order for everything to work properly? Also, I still have the in tank electric pickup around here and will put that back in with the walbro but do I need some other wiring back there or can I use stock fuel pump wiring? Or would I be better off leaving the carb pickup in, and installing an external pump? |
Short answers:
You don't need the TBI engine harness, the LS harness will for the most part replace it. You will only need to wire a couple relays and fuses maybe.
Stock pickup is fine with a Walbro, stock wiring is fine for a stock LS1 but I would want better fuel pump wiring with any added power.
Do not do an external pump, you will hate life.
Long answers:
Idiots on TGO are always looking for a "plug and play" solution to everything. Pocket knows his stuff and has a couple good threads but they are 100% geared towards somebody doing this swap to an unmolested 89+ thirdgen with TBI or TPI V8s. As such, they are useful as reference but they really assume you are going to use the stock fusebox and stock C100 connections for things like VSS, ECU power, O2 power, Check Engine Light etc. If you start with a more gutted or earlier TBI car or god forbid a stock carb car (mine was originally a 5.0 H.O. carb car) then all of the stock harness connections outlined in Pocket's threads are mostly useless. For you, as long as you didn't hack up the stock harness you can probably use most of his wiring guides in reference to the C100 connector on the firewall.
In my case, the connections that the ECU required simply did not exist, and furthermore the wiring in early carb cars is absolutely not documented correctly. Luckily, when I went from carb to MegaSquirt I already took care of all of the necessary relays/fuses to the point of installing an aftermarket Bussman fuse/relay box under the hood of my car. So when I went from MegaSquirt to LS1 things were fairly easy. They were kept even easier by my decision to forgo A/C and cruise for the time being, although I will be adding late model digital cruise control to my setup soon (needs no integration to the ECU). The TGO information is mostly predicated upon the fact that you will be using the LSx ECU to control many factory things like fans, fuel pump etc. In my case, with a carb car, I didn't have any of that factory wiring to control so I had to make my own.
In the most basic sense, the LS1 harness is entirely self-sufficient. It is basically a standalone harness from the factory, we just have to massage things a bit to lighten it up and get it connected to the car. The external connections from my ECU to the car harness are as follows:
Outputs:
Fuel pump relay output to my underhood fusebox.
Fan output to my fusebox.
Speedo/Tach output to my Autometers
CEL output to my custom gauge cluster
OBDII Serial Data to OBDII port under dash
Inputs:
Key switched power
Constant power
Every other thing the ECU needs to run is part of the LS1 harness.
Here is a basic overview of a couple other incidentals:
Fuel pump - Walbro 255 in baffled TPI tank, custom 14GA wiring to pump. Fuel lines are simply a stock TPI feed line with no return (return is off of the Corvette filter back by the tank) -6AN hardware and lines on everything.
Fans - IROC dual fans, wired as single load and triggered by relay.
ODBII - Pulled an OBDII port and pigtail out of a 99ish Blazer at the junkyard, it had the exact same mounting points as my stock ALDL port so it simply screwed in under the dash like factory.
The hardest part of the wiring for my swap was extending the ECU harness about 3-4 feet. I needed to do this in order to place the ECU inside the car and route the wiring through the fender like factory. Some people drill a hole under the heater box which negates the need for harness extension; I thought that was a hackjob on par with cutting a fuel pump access hole so I didn't even consider it as an option. The other option is to find a way to mount the ECU under the hood like a 4thgen, but there is literally no way to make that look acceptable in my opinion without also extending the harness. So, I had to extend it anyway.
You would also have to get a tune to at least delete VATS, but that is easy.
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84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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aaron_sK
Member
Joined: 23 Jan 2006
Posts: 8834
Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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| Posted: Sat Aug 24, 2013 5:49 pm Post subject: |
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| Alphius wrote: | | Idiots on TGO are always looking for a "plug and play" solution to everything. |
All you really need to get pretty much any EFI swap to start in a thirdgen is the 10Ga pink ECM feed. 
Building a new harness isn't a bad idea. Especially a new harness for the ECM feed, alternator, fusebox feed, and fuel pump. GM really had their head up their ass when they wired these cars, especially the older ones. |
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