Help with a stand alone running 2.8 with harness and computer? - S-10 Forum
 
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post #1 of 5 Old 10-14-2015, 11:24 PM Thread Starter
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Help with a stand alone running 2.8 with harness and computer?

Hey guys I've got a 93 S10 i'm doing a carbed 350 swap in. My goal is to see if i can't get my 2.8 to run using the engine harness and computer that i won't need for the 350, and put it in my autocross car (84 fiero) My 2.8 runs way to good and strong to just sit there and if anyone can help me i would greatly apreciate it!

I have the harness that goes to all the sensors and stuff along with the ecm. My main problem is where the other end plugs into the passthrough, i see a bunch of pins which I thought just went through the fuses and back to the harness for the most part, but the don't.. as i'm sure some of you know they go up from the passthrough into the dash, and back through a different set of wires that then lead into the fuse box.. this kinda boggles me, making me wonder if pulling this off is even possible without having the dash harness and fuse box as well. I have no problem with wirring some things up infact i love it, this doens't however mean i claim to know a lot about diagrams and stuff, but if there's a way to get this harness and ecu run my engine alone with tying some loose ends with some fuses and wire, i'm so game, it would do my autocross car a WELL NEEDED favor.. I understand this is an S10 forum but no one else will know that harness and the TBI system as well as you gues will so I'm bere asking the experts

THANKS GUYS!

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post #2 of 5 Old 10-15-2015, 08:50 AM
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Re: Help with a stand alone running 2.8 with harness and computer?

I'm a little confused... your 84 Fiero only came with a 2.5 4 banger. They didn't put the 2.8 in until 87 (?) IIRC. Are you swapping the 2.8 into the Fiero?
The OBD 1 computer and wiring harness is somewhat less sophisticated than the OBD II... as you know. You will have to cut up the wiring harness to achieve your goal.
Basically, the ECU needs power and ground to operate. There are few other inputs from the chassis for these early units. OBD II had VSS, transmission and dash inputs among other inputs.
The out wires from the ECU will be to engine sensors and fuel pump trigger. You will have to divorce other wiring from the wiring harness.
Fortunately, there is little more than the main engine harness and fuel pump wiring. If you disconnect the engine management harness from the engine and remove the plug on the ECU, I think you can remove the whole assembly almost clean. There is another part of the harness that goes to the fuel pump relay, that is where you may have to cut the cover off of the harness and follow wiring to the relay.
I can't help you with specific wire color and pins, there are guys on the forum who know that crap cold. Maybe someone can help out.

S10 addiction:
1)'82 S10, 383, 700R4, Shorty
2) '85 S10, 3.4, 700R4 4x4 stretch cab (Redneck)
3) '90 S10 2.5, 5 speed shorty
4) '91 S10, Built 3.4, 5 speed shorty (Voodoo)
5) '92 S10, 2.5, 5 speed shorty, (Barbie)
6) '92 S10, 2.5 5 speed, Shorty
7) 1979 LUV, Buick 3.8 V6, TH 350 Shorty.
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post #3 of 5 Old 10-15-2015, 12:09 PM Thread Starter
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Thanks for the info bud This is enough for me to regain a little faith it my idea.

To clear some things up. - No, the Fieros never came with 2.8's in 1984. However I have a few reasons for why i think i can do this "easily enough" and why it's worth the hassle.

1. I have a free great running 2.8 Harness & ECU already out of the truck, ready to go.

2. Someone before me put in an 85/86 5-Speed that will bolt directly up and work very well with the 2.8 without grenading Thank you previous owner!

3. This is my autocross car that has alredy been a little molested, frankenstiened, and toggle switched up, so I have inteded to swap a stand alone running engine from the beginning, regardless what engine, I just so happen to have the 2.8

4. The 2.8, while not incredibly powerful, still has arround 30%-40% more Hp & Tq, than my 2.5.. This in my 2500 lbs fiero will be a great gain, especially in the relm of RPM! My 2.5 falls on it's face at 3,700 most of the time. my 2.8 feels strong up to 5k and a little past though it may not be building power still by the numbers. Either way, in autocross this alone will be a huge advantage over the 2.5.

As i dig into my harness, trying to re-cap on what you said, I know i'll probably have some questions later. But considering i will mostlikely be taking some of this on today, i juat wanna make sure i got down what you were trying to explain in a general sens. --

Basicly speaking- are you saying the ecu has "out wires" that can run the sensors & engine as long as the ecu has a power and ground, and the other wires that go from body and chassiss just need to be separated from the harness? Give or take a few acceptions? Like the fuel pump relay system or whatever else?
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post #4 of 5 Old 10-16-2015, 01:16 AM Thread Starter
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Earlier tonight i became extremely familuar with the wirring herness, i am almost finished labeling every single wire on both ends and at the sensors as well as writing it down in a really organized way just so i know the routing of each sensor's wires, and if one goes to the pass through or to the ecu or is connected to another wire, all for later referance, when i knwo what needs power, and what needs cut etc.

My question atm is i see a lot of things wirred into the passthrough and stuff but also have wires going into the ecu but for the same senser, are the wires coming from the ecu the actual operating signals and what not, and the wires going to the passthrough "out signals" for going to the guages and warning lights, that can be cut and not hooked up? If someone has that kind of info on things like the coil, fuel injectors, destributer, MAP sens, and other things that are actually important for pulling this off as well as power and ground(s) for the ecu. that would be amazing even some references to the right wirring diagrams and stuff i can't seem to find.

Example the 2 wires coming out of the coil connecter on the main engine management harness. Coil has to work obviously. The fat pink wire goes to the passthrough connector, my guess is it's the power to oporate the coil, seems how the other wire doesn't go to the ecu. the other wire coming out of it which is white, goes to this square white connecter that plugs in under the dash right next to where the ecu is mounted , i'de be more convinsed that this is a signal wire for a tach and is not necissary for running and could potentially be capped without stopping the engine right? Dunno if this is true about which wire is power or signal, and therefore necissary to run, so this is the stuff i need help with, what wires HAVE to be conected. theres only so many sensers that run this thing there has to be a way to cap all the signal wirres that are extra bs for the chassis and guages etc. You guys probably get my point. Hah

Unless this is literally as simple as trying to find a small diagram for each senser like, coil, map and whatever else goes beyond the passthrough or the square white connector and to a power that i didn't know about.
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post #5 of 5 Old 10-16-2015, 10:04 AM
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Re: Help with a stand alone running 2.8 with harness and computer?

I have worked on many Fieros in the past, so I am a little familiar with them. IIRC, the mounts for the later V6 Fieros will bolt into the earlier models. That makes it more simple.
AND... the tranny bell housing bolt pattern is the same. Make sure you have the right flywheel for the V6. 88 and newer 2.8 had a neutral balance FW.
Form what I remember about the harnesses, the sensor wires are mainly stand alone for the ECU. They have weather pack style connectors.
The temp, oil pressure, alternator, coil all have wiring independent of the ECU harness. They may be in the harness itself, but do not have input into the ECU.
For example: The ECU has a its own temp sensor. The temp light/gauge in the dash has a separate sensor from the ECU.

Another example: The coil has separate power from the ECU. The distributor has a sensor in it that sends a signal to the ECU so it knows what the ignition/cam position is doing.

The main wires that are independent of the chassis harness are the fuel pump trigger wires for the FP relay.

The engine sensor wiring harness is stand alone = for the ECU. Anything in the harness that doesn't go from the engine to the ECU is usually not needed.

OK... list of ECU wires
1. Temp sensor
2. Oil pressure sensor
3. TBI injector trigger wires
4. IAC wires
5. MAP sensor
6. EGR trigger wire
7. Distributor signal wires.
8. TPS wires

Better yet...
http://www.justanswer.com/chevy/3atm...r-code-89.html

S10 addiction:
1)'82 S10, 383, 700R4, Shorty
2) '85 S10, 3.4, 700R4 4x4 stretch cab (Redneck)
3) '90 S10 2.5, 5 speed shorty
4) '91 S10, Built 3.4, 5 speed shorty (Voodoo)
5) '92 S10, 2.5, 5 speed shorty, (Barbie)
6) '92 S10, 2.5 5 speed, Shorty
7) 1979 LUV, Buick 3.8 V6, TH 350 Shorty.
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