I'm trying to remove the wiring harness out of my 84 vette to replace it with the TPI style harness. I have everything removed and labeled from the motor and just hanging in the engine compartment. It passes through the firewall on the passenger side of the car through a rubber grommet. I unhooked the 2 large connectors at the ECM under the dash. What else must be disconnected to get this out? I feel like just gettin shears and cuttin the dam thing off at the firewall as it's holding up progress. THANK YOU FOR ANY AND ALL HELP Pipe

 

on the 96 engine harness there is a bolt that goes through it.

 

removed pic

 

I removed the one from the drivers side that had the single bolt going through it. It was mainly for the front lighting harness and I think the other only had a few engine functions on it elec.fan and fan relay and not sure about the alternator. I'm trying to get the main harness out. THANKS FOR THE REPLY'S Pipe

 

the main harness falls behind the engine, into a hole.

it does connect inside the car... it's a real bitch, if you want my opinion.

It connects up to the DIC, IP and climate control panel (fans and such).

You should get a pin popper to do it right.

 

Ok. 96 must be different.

rob

 

On a '96, the ECM is mounted in the engine comparments. I believe on the earlier models, the ECM is mounted under the dash.

 

Yep the WCM is under the Breadbox on the passenger side of the 84. I removed the 2 large connectors from the ECM. It looks like wires go to the fusebox and over to the DIC and Gauge Cluster. Don't tell me i'm going to have to tear the whole dash and DIC and fusebox out of the car? Pipe

 

Bill - weather it looking good this weekend so I am going to be pulling the engine harness out of my '85. I am also pulling the entire dash so mine is definitely coming out. Let me know if you don't get yours out by this weekend and if you want I can give you the skinny on exactly what is involved, exactly where wires go ect. I did this last winter but honestly can't remember what exactly is involved. I had my dash out last winter and changed my entire dash harness so it was a little different procedure last time around.

 

On the 86 the dash harness is separate from the engine harness, the fuse panel is part of the dash harness I can take a picture of the dash harness if you want as it is in the trailer right now I sold the engine harness so I can't go look at that.

 

Vtvette THANK YOU SO MUCH I won't touch anything till I hear from you on how you removed yours. I'm sure they are really close to being the same. The crossfire is out of the car and the wires to the engine are labeled and ready to be pulled through the firewall and into the inside of the car and get disconnected so I can swap the harness out. I'm either going to race the other vette or go to Maple Grove Dragway's flea mkt. to try and sell some of the vette parts I don't need anymore. Please get back to me on this after you remove your harness. THANKS AGAIN Bill (Pipe)

 

Will do Bill

 

Well I worked on getting the harness out of the '85 this weekend. Didn't have as much time as I hoped for so it's not all the way out but it's damn close.

Under the dash I had to disconnect these connectors:



That looks to be it. These connectors all come from the ECU connector, they are about one foot down from the wiring loom from the ECU connector. There is also a vacuum line connector (white, two ports) that goes to the heater control unit. The connector is back a little ways behing the heater control head unit. That looks to be it. From there pull the wires through the firewall (my '86 harness is a square base where it attaches to the firewall, the '85 and I believe the '84 is a round grommet). From there the main harness goes around the back of the engine (and a section goes down to the tranny, another goes off to the engine sensors fuel injectors etc), over to the wiper motor, down around the brake booster and ends up at the large bulkhead plug behind /under the battery. This large connector is actually two parts an upper and a lower. The lower part goes forward to the headlights etc the upper part is the end of the engine harness. Disconnect the upper part of the harness from the bulkhead connector to remove the engine harness from the car.

Now, this is how it is on '85 to '89 cars. I have heard there are some differences to '84 harnesses. I don't know exactly what the differences are.

Let me know if you have any other questions,

 

Brian thanks for the help. After I saw your pix I went out to the car removed the passenger seat layed under the dash and looked for similar connectors and cut some wire ties off and traced the wiring. I got a small screwdriver and undid the plugs and the harness came loose. I had a hell of a time fishing it through the firewall but it came out THANK GOD. Some of the wiring under the dash is still a mess that I still have to sort out. They had wires going into the Fusebox that were tapped into fuses for power and an aftermarket stereo plus a manual fan switch and other stuff. Do you know if the connectors from the 84 will fit into the 90 and later style TPI ECM and all the dash functions work or will I have to change the dash harness also. THANKS AGAIN Brian Bill

 

Bill - glad to hear you got the harness out.

As far as a 90 harness it's a completely different animal. The 1990 engine harness doesn't pass through the firewall at all. It's all contained in the engine compartment along with the ECU. The entire dash is also different in a '90 so the wiring is completely different.

Aside from the connectors in the picture I attached, and the possibility of having to change a few pins on the bulkhead connector portion of the engine harness (and I don't even think that would be required) the rest of the engine harness from a '86 to '89 should be plug and play with a L98 TPI engine. My only concern would be if your '84 dash harness doesn't have the connectors shown in the picture I posted. Then you would have to figure out where each of the wires from the connectors go and incorporate them into your '84 harness.

So - does your '84 harness have the connectors in the picture above?

 

Hey Brian the one connector is the same as in the pic the lower one in the picture is the same but the other two are different plus there are two more flat style connectors that came through the firewall. I plan on getting the TPI style harness (speed density) from a 90 or later style car from Howell Engine Development and i'm hoping that the connectors will match up. I'm thinking I might have to send them my harness for a rework so they can use my connectors to work with their system. I have their catalogue and it says they do reworks I had no rest in my *** I just had to have this 84 cause it was cheap. I should have waited and just looked for a 85 or later car with the TPI and I wouldn't have to go through this. I sent Howell an E Mail about a week ago and they haven't awnsered it yet guess I better call them. If ya have any more thoughts about any of this let me know. THANKS AGAIN Bill

 

Well Bill no point regretting the decision to buy the '84 whats done is done all you can do now is get it together the way you want it. What are your plans for the car? That will determine how to go about this project.

 

You will have MORE of a headache getting the 90 Vette SD harness to work.. I suggest getting a harness from an F-body or have Howell build a custom harness if they will do it.. Basically connector locations like an 89 MAF car but have it configured to use the 7730 ECM from the F-body.. smae guts as the Y-body 7727 just a different case.

When I swapped my 91 dash into my 89 I found it was easier to swap to the 91 engine harness then mess with the 89 one..

HEY VT,

how is the swap coming?

 

Hey Jeff still finishing up the wife's Quattro Coupe. Now that the weather is getting better I've started to pull the interior out of the '85 at the house. Wife's car should be done in a few weeks then the Vette comes to the shop and the real work begins. I ordered the '91 factory Electrical manual earlier this week to make better use of the info you sent me and I think I'm going to pick up a full factory '91 manual as well. I've got all the parts I need at this point with the exception of two dash vents I'm watching E-bay for plus I had my entire interior/wiring out last year so it shouldn't take too long once I get going.

I was thinking the same thing reguarding Pipe's situation - SD will only complicate things unless he gets the Howell harness. The Howell harness will make the engine harness itself a snap but then he will want to go through the factory '84 engine harness and pull out the engine wiring but retain the wires that come out of the bulkhead connector for the wiper motor etc. There are some other wires bundled with the engine harness that don't actually go to the engine.

If he goes with the Howell harness he will lose the MPG, miles to empty etc functions. No big deal but if he wants the car 100% factory in function than the Howell might not do the job.

I guess his options are: Howell engine harness along with modified stock harness or another option which would be cheaper but require a little more labor is to get a dash and engine harness from a '86 - '89 car and swap both in and be done with it. This will keep everything 100% stock and I'm pretty sure it's 100% plug and play even in a '84.

Depends on Pipe's comfort level with tearing his car apart. Personally I would go the dash/engine harness from a '86/'89 but I don't mind tearing interiors apart

I'm sure the cost of having Howell modify a harness for use in the Vette to make it tru eplug adn play will be big, big bucks.

 

Which 2 vents? I might have them, PM me with the ones you are looking for.

Another option if he wants to learn how to tune is to use the 84 harness and Buy the EBL from Dynamicefi.com

He will need a different ECM I think. my buddy has this on his 84 and likes it, but is thinking of upgrading to a Miniram and using the same ECM.. with that ECM and code his dash will still work