Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

TBI wiring harness help.....(pictures)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlueOx, Jun 28, 2002.

  1. BlueOx

    BlueOx 1/2 ton status

    Joined:
    Aug 6, 2000
    Posts:
    239
    Likes Received:
    0
    Location:
    Houston, Tx
    I just got the TBI set up and wiring harness but, I have some questions. I asked the guy I bought it from what year vehicle it came off of but, he was unsure. He stated it came off a truck ; maybe 1992. I spent most of the day a the library looking up wiring diagrams for 91-95 trucks but no luck. I'm just waiting in the books I ordered to really get started, but I have a few questions. I do believe there are a few things missing off the harness. I posted a few pics of the harness for ya'll to look at. There is a white plug on the harness near the computer that I can't find in the books, might be the ALDL. There is also a big Black/Gray plus of some sort about 1 1/2" away from thecomputer, it looks like this is the piece that was on the firewall...what is it and do I need to cut a square whole in the firewall to get it in there? One last thing on the harness there is a part the looks like it was bolted to the junction block one the diverside firewall...what is that and do I need any of that. I might need to get more of the harness at a junk yard. Could the TBI Masters that are on this site look at the pics and tell me what some of these things are and or what year harness it came off of.
    Thanks,
    Charles

    TBI pics
     
  2. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    The big white one that's near the computer (Your picture that's labeled h1) normally plugs into the dash harness. You'll probably find that the ALDL data goes out of that plug. Every wire in the harness has a unique color/stripe, so it should be pretty easy to track down what goes where once you have a wiring diagram.

    You should be able to determine more about the harness using the part number of the computer. Look on the Edelbrock web site at www.edelbrock.com in the tech section for their MPFI system. I recall seeing a chart in there that lists many of the computer part numbers and the correspnding vehicles and years that they were used. /forums/images/icons/cool.gif

    That big honkin' gray header (at the left side of pic h2) is indeed the one that goes through the firewall. Note that this is NOT a connector, so don't try to pry it apart. /forums/images/icons/wink.gif It's just a very fancy grommet that all of the wires pass through. GM goes to great pains to NOT have any intermediate connections in the wiring harness that could corrode or otherwise compromise the signal integrity of the harness. Be careful when you cut the hole in the firewall for this, as you don't want to set the insulation behind the firewall on fire. /forums/images/icons/shocked.gif

    I'm not sure what that is in h3. /forums/images/icons/frown.gif That must be something for the later models. My '87 'vette harness doesn't have anything that looks like that.

    The black connector in h4, with the bolt in it, probably goes to the fuse block. You'll have to figure out which of those wires you do need and which ones you don't need. It's been a very long time, but I think I found stuff like wiper/washer power, a/c clutch power and EGR solenoid power in that part of my harness. You'll need the EGR solenoid power, but the others are not required. /forums/images/icons/wink.gif

    I'll take a closer look at the toys in my driveway to see if I can help you determine the year and where some more of that stuff goes. I've got the '87 'vette engine in my K5, plus I've got a '90 Suburban and a '94 Suburban. If your harness is from a '92, I'd think it is pretty similar to the one in the '94 Suburban. /forums/images/icons/cool.gif
     
  3. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    I was looking through the rest of the pics and figured out that h3 and h4 are the same connector, just shown from different angles. /forums/images/icons/blush.gif You'll most likely find that you don't need most of those wires. /forums/images/icons/cool.gif
     
  4. BlueOx

    BlueOx 1/2 ton status

    Joined:
    Aug 6, 2000
    Posts:
    239
    Likes Received:
    0
    Location:
    Houston, Tx
    Thanks for the info
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Well come to think of it Harry, what does your "H3" stand for. I've got to work on the "boy" in Blazer_Boy, I'm gonna be 20 here in a few months. Boy I should save this for a PM, but I'm too lazy. The Blazer is still in the same shape. Panel is ready to put on, just have to wait until my painter has time.
     
  6. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    My last name and I'm the third. /forums/images/icons/shocked.gif Clever, eh? /forums/images/icons/wink.gif BTW, enjoy being a "boy" as long as you can! /forums/images/icons/cool.gif
     
  7. Mudzer

    Mudzer 1/2 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    3,639
    Likes Received:
    0
    Location:
    Missouri
    I have spent many hours sorting wiring for an 87 TBI harness and I believe I have decent knowledge on this subject. First of all, what are you installing this TBI on? If your truck is Non-TBI then you will not be able to use the firewall bulkhead (black plug) because your fuse box will not have the appropriate fuses to run the TBI. So, basically you will build a "Stand Alone" wiring system for your TBI. In looking at the photos, I see many things you can discard, unless you want this wiring harness to contain these items:

    Oil Sending Unit wiring
    Temperature Sending Unit wiring
    Alternator Wiring
    Washer Pump wiring
    and any underhood electrical device not required to run by the TBI

    These things can be removed to "simplify" the wiring and make future troubleshooting easier. Basically, by eliminating these things not needed in the TBI system, you can make your TBI system separate from your existing system (Oil pressure gauge, Temperature gauge, and alternator wiring). Now, do not confuse the temperature sending unit with the temperature switch, which IS needed for the TBI system. Same with the Oil sending unit and Oil Pressure Switch - again the switch IS needed for the system.

    You can use the firewall "grommet" (gray box) if you want to make a clean break through the firewall. You never want your wires to become in contact with sharp metal, they rub and cause shorts.

    Now back to the wiring. When deciphering my wiring system and creating a "Stand Alone" TBI wiring harness, I was able to narrow the connections down to 12 wires needing connected to a fuse panel, VSS, and ground. I need to get out my notes and explain these further. I will report back in a day or so.

    I bought a VSS from a wrecked Suburban which had the same style gauges as my 78. I removed only the speedometer with VSS and the VSS buffer and spliced it into my system.

    The system I started with came from an 87 Chevy Van equipped with a 305. It is being installed on a 350 so some changes will need to be made. Namely a pressure regulator will be added to bump up the fuel pressure, and new 350 injectors will be installed. Plan on buying a Painless Wiring 7 fuse panel, they work nicely for this application.
     
  8. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    I think I will have to enjoy being Blazer "Boy". I think I've met future Blazer_Girlfriend the other day. Then I suppose in a few years it'll be Blazer_Wife, and then Blazer_Kids, then Blazer_Mortage. Oh God, sounds like its all down hill from here.
     
  9. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Ahhh, that's rare, a young one with enough sense to see that now... /forums/images/icons/laugh.gif
    Enjoy life while you can. The opportunity will be severely diminished soon enough...
     
  10. BlueOx

    BlueOx 1/2 ton status

    Joined:
    Aug 6, 2000
    Posts:
    239
    Likes Received:
    0
    Location:
    Houston, Tx
    Mudzer I'm installing the TBI on an 85 Blazer. I don't know the exact year the system came off of because I bought is "as is". I called the dealer and gave them the PN on the ECM and they told me it came off an 88-92 truck. I have looked at many wiring diagrams at the library and they all look the same. What I need to do is go find a wrecked truck in that year window and get the wiring harness for the white 15 pin connector near the ECM. I just got the TPI/TBI swap book and it has good info in it but I need more. My biggest problem I have is identifying the wires that need to be connected to the fuse pane. I have looked at the diagram of the ECM and all the wires that go to it and can't figure some of them out. It looks like there are many wires that need to be connected to a power source.

    A6 Power Input pnk/blk...states is goes to ECM/IGN fuse does that mean that it needs to be hooked up to the IGN switch?

    C9 IGN ppl/wht...states is goes to the crank fuse. What would I hook this up to?

    What about the Red/Wht wires that leave the injectors. The book states they go to INJ A/B Fuse. Do these hook up to a HOT lead too.

    One last thing today what is the best/cheapest way to run my fuel needs, ie. fuel pump, lines, and filter. I looked at the fuel pump relay; are there supposed to be wires that hook up to the fuel pump?

    I know there are many questions that I'm asking but I can read all the books I can find and not get as good as info as you all give me. I have searched the site as far back as a year and got a lot of info but I just need more. I any one can help me out I would be grateful. If some has taken notes/pictures please break them out.

    Thanks,
    Charles
     
  11. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Well, I can't help much on the wiring. I just got the entire dash/ECM/engine harness from the donor and swapped everything.

    As for fuel, you've got several options. I prefer the in-tank pumps because they are MUCH cheaper and they last longer. Only down side is changing them if they go out. You have to drop the tank if you don't make an access door. If you decide to use the in-tank pump, you can get a pickup/sending unit from a junkyard donor. Just look for the same size tank you have so that the length will be right. You can also modify your current pickup to mount a pump by cannibalizing an otherwise unusable sending unit. Probably best to try to find the right one though, I had a hard time initially because I was looking for a saddle tank and the only model that works is an 87 that happened to come with TBI (very hard to find). I wound up modifying a TBI sending unit from a different tank to fit in my diesel tank.

    The lines are another story. Do you have the TBI steel braided lines? If not, you may want to scout up a pair, dealer has them but $$$. I got the braided lines with the engine. The fittings on the TBI and on the end of the braided lines are a funky metric o-ring that is hard to find parts for. I stripped the lines off a donor vehicle to cobble together a fuel system for my rig. When I needed to run custom hard lines (avoid rubber for most of the system) I cut the o-ring ends off the donor lines and double flared them (just buy some double flare nuts) so that I could use standard hard lines (ask for brake lines at any part store).

    That’s all I can think of now…
     
  12. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    </font><blockquote><font class="small">In reply to:</font><hr />
    A6 Power Input pnk/blk...states is goes to ECM/IGN fuse does that mean that it needs to be hooked up to the IGN switch?

    C9 IGN ppl/wht...states is goes to the crank fuse. What would I hook this up to?

    What about the Red/Wht wires that leave the injectors. The book states they go to INJ A/B Fuse. Do these hook up to a HOT lead too.

    [/ QUOTE ]

    OK, A6 needs to be fed by a circuit that is hot in start and crank, through a 3 amp fuse.

    C9 needs to be fed by a circuit that is hot ONLY in crank, through a 3 amp fuse. This is how the ECM knows when you have the starter engaged, which kicks it into a different mode. It allows fuel enrichment during cranking (think of it as the EFI equivalent of a choke). If the engine should get flooded, it will also lean out the mixture if you hold the pedal to the floor while cranking. /forums/images/icons/cool.gif

    The injectors need to be fed by a circuit that is hot in start and crank, through a 10 amp fuse. You also need to provide power to the EGR solenoid. I'm looking at the book for an '87 truck, which shows that the EGR solenoid gets its power from the same circuit as the injectors, via the same 10 amp fuse. This may be different for your setup. You'll need to confirm on a later set of prints.

    You also need to provide an input on B10. It needs to be grounded when the tranny is in park or neutral (assuming you have an auto trany, and the truck the ECM came from also had an auto tranny) and open when the truck is in gear. No fuse is required in this circuit.

    The easiest way to install a secondary fuse panel for all of this stuff is to use a Cirkit Boss from Painless Wiring. You can find them at http://www.painlesswiring.com/fuseblock.htm /forums/images/icons/cool.gif
     
  13. BlueOx

    BlueOx 1/2 ton status

    Joined:
    Aug 6, 2000
    Posts:
    239
    Likes Received:
    0
    Location:
    Houston, Tx
    HarryH3, let me start by saying thanks for thr info. When you say that C9 needs to be fed by a circuit that is hot ONLY in crank. What is ment by that. Does that menn that has to be hot only when cramking or stay hot after cranking?What wire would be a good source for that?

    As far as the EGR solenoid goes is that also called the EGR CTRL (A4)? I looked at the diagram and thats the only thing that says EGR on it. Where is it located?

    Thanks again,
    Charles
     
  14. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    C9 has to be hot ONLY when the starter is turning. You can pick up that signal from the wire that goes to the starter solenoid. /forums/images/icons/cool.gif Just put a 3 amp fuse inline with the wire to C9.

    The signal from the ECM to the EGR solenoid just provides a ground for the solenoid. The power comes in from the other side of the solenoid. I was looking at the quickie prints in the driveability section of the manual, but it looks like it might be tied into the injector power lead in the harness already.
     
  15. BlueOx

    BlueOx 1/2 ton status

    Joined:
    Aug 6, 2000
    Posts:
    239
    Likes Received:
    0
    Location:
    Houston, Tx
    OK, I think I got it all now but there are a few more question. I was looking at all the wiring diagrams and could not find any wires that led from the fuel pump to the fuel pump relay. Where does the fuel pump relay come into play with the fuel pump? Where do the fuel pump wires hook up to? Thats the last one for now.

    Thanks for all the help guys,
    Charles
     
  16. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Power to the fuel pump should come off of pin E on the fuel pump relay. It's the center pin on the relay. /forums/images/icons/cool.gif
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    BTW, if it helps any, in '88 on TPI setups that white/clear plug is called the "IP connector" wo you may see it referenced as that. 15 pins.

    On my '88 TPI, it has 3 ALDL wires, as well as the power leads to the ECM, and some other things I can't remember right now : )

    www.thirdgen.org has a couple of TPI wiring diagrams up in the FAQ I think it is, and I wouldn't be surprised if they arne't quite similar, even wire color, if you don't have your own wiring diagrams yet. Never hurts to have references!
     
  18. Chris Demartini

    Chris Demartini 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    2,406
    Likes Received:
    1
    Location:
    Dumont NJ 07628
    <font color="blue">Heres a picture of the fuel pump circuit for my 91 TPI (if it doesnt work, copy the url of the picture). TBI shouldnt be much different.

    [​IMG]

    Can anyone tell me how the oil pressure switch works? My harness is missing that and I need to get this thing together by next week, can I just jump the gray wire to the wire going from the relay to the fuel pump? /forums/images/icons/confused.gif
     
  19. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    The oil pressure switch is in parallel with the fuel pump relay contacts. If the relay fails, then the pump will still run as long as the engine has oil pressure. /forums/images/icons/cool.gif If the relay is good, then you really don't even need the oil pressure switch. It's just there as a backup.
     
  20. Chris Demartini

    Chris Demartini 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    2,406
    Likes Received:
    1
    Location:
    Dumont NJ 07628
    <font color="blue">OK cool /forums/images/icons/cool.gif So I don't need this gray wire?
     

Share This Page