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Old 02-13-2017, 04:49 PM   #1
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Holley hp efi

OK so I bought a Holley hp efi system to run on my 1986 iroc with a modified small block, figuring the plug and play was the way to go. I removed the main wiring harness from the engine bay along with the ECM. Does anyone have a wiring diagram for the harness under the dash that plugged into the main wiring harness. I can't seem to find it anywhere. Any help with this would be appreciated. Thanks.
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Old 02-13-2017, 05:04 PM   #2
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Re: Holley hp efi

Austin thirdgen wiring site should have it
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Old 02-13-2017, 05:31 PM   #3
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Re: Holley hp efi

I looked there. I need the harness pinout more specific. Need to know what these wires are for.
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Old 02-14-2017, 11:18 PM   #4
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Re: Holley hp efi

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Originally Posted by crossrush View Post
OK so I bought a Holley hp efi system to run on my 1986 iroc with a modified small block, figuring the plug and play was the way to go.
FYI - It is not plug and play.

The opaque connector is C207. I was never able to find complete documentation for my '89 Firebird either. I ended up backwards engineering it by spending time with a multimeter doing circuit checks. In short, I found most of it is power taps from various fuses, plus a few other things. This is how my car is configured, which will not match your car, but it will give you something to work with so you can do your own circuit checks. Hopefully somebody can post with more relevant info from '86 Camaro but I'm sharing this in the absence of that info.

Pin-----Color----------Purpose

A-------BRN-----------unknown, never did figure it out
B-------PNK/BLK------INJ fuse (10 amp)
C-------BRN/WHT-----Service Engine Soon light bulb in dash (ground side)
D-------BRN-----------FAN fuse
E-------WHT/BLK-----unknown, never did figure it out
F-------PNK/BLK------ENG-IGN fuse (10 amp)
G-------PNK/BLK------GAGES fuse (10 amp)
H-------TAN/BLK------unknown, never did figure it out
J--------ORG----------Datalink connector (the OBD connector)
K-------BRN-----------Vehicle speed sensor (input to the VSS buffer box)
L-------BLU------------VATS (communication between VATS and the ECM)
M-------BLK/WHT-----Ground (must be grounded)
N-------unused
P-------unused
R-------PPL/WHT------CRANK fuse (3 amp)

Last edited by QwkTrip; 02-14-2017 at 11:24 PM.
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Old 02-14-2017, 11:45 PM   #5
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Re: Holley hp efi

Did you install the same System? Did you use any of the harness to run the holley hp Ecu?
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Old 02-15-2017, 12:12 AM   #6
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Re: Holley hp efi

Yes, I have HP EFI with my LS engine swap.

I chose to install an underhood power center (fuses & relays) for everything engine related. I put a list of links in my build thread that I thought might be of interest/useful to other people. There is a section on electrical. Give it a quick scan and maybe something might catch your eye. If not, that is fine too.

https://www.thirdgen.org/forums/ltx-...ml#post5028823 (What ever happened to QwkTrip's car anyway?)
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Old 02-15-2017, 12:35 AM   #7
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Re: Holley hp efi

Consequently, I made very little use of C207. Most people do, but I did not.

I don't think I ever posted what connections I made at C207. If I remember right, I used one of the fuses to power my Dakota Digital speedometer signal conditioner (SGI-5), used terminal M to ground the SGI-5, and ran the alternator excitation wire through terminal C so that the Service Engine Soon bulb lights up when the alternator isn't working. I think that was all I used.
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Old 02-15-2017, 07:43 AM   #8
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Re: Holley hp efi

I scanned through the thread on your build and I think I'm in a little over my head. I knew I should have just stuck a carb on the motor and been done with it. I'm not that knowledgeable with relays and wiring. I may have to look for some hired help on this one if I keep the holley system. Thanks for the help.
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Old 02-15-2017, 09:36 AM   #9
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Re: Holley hp efi

Crossrush, You should be able to get the holley setup running independent of the C207, If you wish to. Which holley harness do you have ? They have a few main harnesses and a few subharnesses. The holley harness has a fuel pump relay that is wired to power everything (injectors etc)

The C207 was how the original injectors got power and the vss signal pass thru to the ECM. Also there's various emission and ALDL conections in there. Since your car probably has a cable speedo you wont have to worry about the VSS stuff. You could re-use the C207 pins that supply injectors power but will have to add your own wiring to the holley harness to do that
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Old 02-15-2017, 10:37 AM   #10
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Re: Holley hp efi

I have part # 550-601 for the tpi set up. I have a first tpi intake. Like i said before its just a little complicated for someone without a lot of wiring knowledge. Any help is appreciated.
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Old 02-15-2017, 11:42 AM   #11
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Re: Holley hp efi

Quote:
Originally Posted by crossrush View Post
OK so I bought a Holley hp efi system to run on my 1986 iroc with a modified small block, figuring the plug and play was the way to go. I removed the main wiring harness from the engine bay along with the ECM. Does anyone have a wiring diagram for the harness under the dash that plugged into the main wiring harness. I can't seem to find it anywhere. Any help with this would be appreciated. Thanks.
When you say removed the main harness did you also take off the C100 connector . Which is part of the main engine harness ?(located behind master cyl ish) ?
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Old 02-15-2017, 12:19 PM   #12
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Re: Holley hp efi

The harness that comes out on the drivers side is still there.
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Old 02-15-2017, 12:34 PM   #13
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Re: Holley hp efi

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Originally Posted by crossrush View Post
The harness that comes out on the drivers side is still there.
The C100 has 2 seperate harnesses on the front side of firewall. One is the lighting harness, One is the engine harness. If you took your whole engine harness including ECU connectors off without cutting anything, You should have had to unbolt the engine side of C100 too. The engine side of C100 is how all the power gets into the dash/fuse box etc

Ref this excellent thread by Pocket :

https://www.thirdgen.org/forums/ltx-...p-3rd-gen.html (How to prep a 3rd gen harness)
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Old 02-15-2017, 12:45 PM   #14
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Re: Holley hp efi





That harness is still there. I just removed the passenger side harness and unplugged the computer from under the passenger side dash.
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Old 02-15-2017, 01:00 PM   #15
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Re: Holley hp efi

What engine did your car have from factory ? Carb or TPI ? Elec fan(s) ?

So, See that group of 3-5 thick red wires and fusible links and ring terminals at the end of that harness ? Those red ones go to the starter batt term and are the main (only ? depending on year) source of power to feed the dash/fuseblock. Theres also a thick purple wire in there that goes to the starter solenoid to start the engine. All those will need to be connected up if you want the car to run right (dash/lights/etc). You can either reconnect them to the starter, or re-route them to a new terminal block you fab up.

I would be wanting to deal with all that before worrying about the C207.
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Old 02-15-2017, 02:02 PM   #16
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Re: Holley hp efi

Car had a 305 tpi originally with single electric fan. I have dual fans going in. I have the new relays for them. I am just trying to figure out where the best place to tie the holley system in.
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Old 02-15-2017, 02:20 PM   #17
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Re: Holley hp efi

That holley ECU/Harness is fully standalone. You dont need any of the C207 wires. You just need to hook it up to battery pos/neg, And run 12v switched to the free wire. If you reconnected those thick wires on stock harness to the starter, and also the thick pink that goes to the coil, Technically it should run at that point. If you want to integrate things more, you will need to take apart the existing car harness in the C100 area to get at the wiring.

Where do you plan to mount the ECU ? I dont know if the holley harness is long enough to mount the ECU in the stock underdash location. Generally the harness has to be about 10 feet long to the farthest connector (usually TPS and IAC) to underdash mount. Of course the holley is hardened so can be engine room mounted.

On the Fan relays, you will have to come out from the main harness Inputs/out connector and make connections from there, and setup the ecu in software to run those items. You may have to buy another harness to access those in/outs if it did not come with one :

https://www.holley.com/products/fuel.../parts/558-400

Last edited by 88Greg; 02-15-2017 at 02:23 PM.
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Old 02-15-2017, 02:50 PM   #18
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Re: Holley hp efi

Thanks so much for the help. It makes things a little more clear. I called holley tech support and they told me about the harness you mentioned. I am placing an order for the harness along with fuel and oil pressure sensors to use with the efi. Also the harness was long enough to get the ecu to mount close to the factory location.
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Old 02-15-2017, 03:36 PM   #19
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Re: Holley hp efi

QwkTrp's thread there is very informative. I know it seems huge; but it looks like he has encountered and solved every possible stumbling block in such a swap. His is an LS, but the wiring to the holley is very similar to what yours should be like. It would be good to spend a weekend reading it.
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Old 02-15-2017, 04:21 PM   #20
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Re: Holley hp efi

I did look at it quickly but yes i do have to go over it and read it completely. I have found a couple threads where guys have installed this but i needed more specific details to my application. Im just trying to understand this more clear before going any further.
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Old 02-15-2017, 08:29 PM   #21
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Re: Holley hp efi

You don't need to pay much attention to how I did power distribution. Just change that to suit your situation.

What you do want to pay attention to is how I did AC and dual fans. It is elegant and I have a lot more control of those things than if you follow Holley's recommendations.

I also figured out how to get a speed signal into the ECM. Holley doesn't know how to do that with our type of speed sensors.
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Old 02-15-2017, 08:35 PM   #22
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Re: Holley hp efi

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Originally Posted by crossrush View Post
I scanned through the thread on your build and I think I'm in a little over my head. I knew I should have just stuck a carb on the motor and been done with it. I'm not that knowledgeable with relays and wiring.
I'm not going to lie, it was a pain in the ***.
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Old 02-15-2017, 10:38 PM   #23
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Re: Holley hp efi

Going the ls route must be a lot more complicated I'm guessing?
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Old 02-15-2017, 10:54 PM   #24
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Re: Holley hp efi

The output from the stock yellow box VSS converter is useable by the holley ecu.
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Old 02-15-2017, 11:13 PM   #25
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Re: Holley hp efi

What is this used for?
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Old 02-15-2017, 11:23 PM   #26
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Re: Holley hp efi

TCC clutch control for one thing. Can also use it to make a "flight idle" bump when car is moving. Also could be programmed to replicate the T56 reverse lockout with proper wiring.
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Old 02-15-2017, 11:37 PM   #27
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Re: Holley hp efi

Yeah. I have some homework to do.
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Old 02-16-2017, 12:16 AM   #28
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Re: Holley hp efi

Let me ask, are you under the impression that with this self-tuning EFI you can just start up the car and go for a drive and it will tune itself?

I was. It doesn't.

I didn't want to have to learn how to tune so I bought what is hailed as one of the most advance self-tuning systems. I consider myself a victim of dishonest advertising. The only thing it does is adjust fuel maps, which is the easiest part of tuning. And it can't even do that worth beans at idle. All the details that really matter, the things that make the car drive well, start well, idle well, detect knock..... it's all up to you man. And there are no diagnostics when something goes wrong. It's just you and a pile of data logs that you have to pour over.

Furthermore, I have found it very difficult to find speed shops that will work with HP EFI. Before you get too far into this, you might want to make sure the reality meets up with the dream. Sometimes a carb is the way to go.
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Old 02-16-2017, 12:22 AM   #29
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Re: Holley hp efi

I did buy it based on the fact that a Holley rep did tell me just that. I was told it controlled everything. Fuel, timing and even lock up control for the 700r4. I will have stop and re think the build. Too bad I already have sunk all the cash into it already.
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Old 02-16-2017, 12:32 AM   #30
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Re: Holley hp efi

Technically true, it can control those things according to the data & rules that you load by hand.
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Old 02-16-2017, 09:19 AM   #31
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Re: Holley hp efi

The important thing will be to start with the right base tune. There are several included with the holley software for a variety of combos. You will need to get some basic settings right in the configuration (injector size etc).
The base tune will get your spark map close enough. Certainly waaay better than any mechanical distributor setup.

Theres no reason a shop could not handle the Holley tuning, If they truly understand tuning. As opposed to a shop that just downloads tunes off a repository and charges you $300 to burn it into your stock ecu.
The holley fuel map is very similar to other aftermarket ECU's in its layout.

Yes the self-learning part is not perfect and universal. The engine has to run and be fully warmed for it to begin working. And there are areas of the map where manual tweaking will be neccesary.

Whats the alternative ? Carb ? really ? What better EFI system is there out there Qwk ?
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Old 02-16-2017, 06:17 PM   #32
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Re: Holley hp efi

I am helping him adjust expectations. I've been where he is and that is why I can pretty much read his mind.
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Old 02-16-2017, 06:27 PM   #33
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Re: Holley hp efi

Unfortunatly. I already have too much invested in this set up, so i am going to have to stick with it and figure it out. Im just going to leave it for now and going to another part of the car until i can do so more homework on this money pit.
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