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GM TBI Schematics

Discussion in 'The Garage' started by 84_Chevy_K10, Feb 8, 2005.

  1. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I need a copy of the GM TBI Schematics. I had a set but they are gone now that my computer crashed.

    I'm thinking I can get EFI in before ECBB and I've talked about it forever. I've got an entire donor truck at this point so I'm out of excuses.

    I am seriously considering getting started tomorrow.
     
  2. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    hmm, i've got it for 87.. just picked up the jumbo wiring manual off the Bay.. my scanners not working tho... hmmm, maybe i could take a pic... i'll check into it...
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    What do you need the manual for? You've got the donor, pull all from it, install in other as removed, done! :p:

    Don't people have the TBI manual(s) up in webshots? I know links have been posted before.

    This work?
     
  4. Mudzer

    Mudzer 1/2 ton status Author

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    Tim,

    Not much help in the way of a diagram, but I have spent countless hours weeding through GM TBI wiring harnesses and readying them for retrofit into older vehicles. One thing you will want to do is simplify the harness - get rid of the original vehicle wiring for starter, alternator, guages and so on.

    Make the TBI wiring as if it were a stand alone system.
     
  5. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    Tim I just gave my manual to a buddy of mine and fellow member Ill see if he wont mind taking a few pics for you. I have taken a bunch of pics for Dorian at one time or another and they might be on my webshots, Ill take a peak...
     
  6. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    pics came out like sh*t on mine... guess my camera sucks... wish my scanner was working....
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

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    That's what I was planning on doing. Dorian seems to think I'm going to wire it like factory. Sure. :grin: So much useless crap, I'm starting by eliminating the fuel pump relay and its associated oil pressure switch. This is a trail truck. Wherever I need to put +12 to get this truck to start, that's what I'm doing, and hooking up the sensors and I'm done with it.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    I think your going to find that the "so much useless crap" isn't as plentiful as you think.

    Theres some emissions stuff (EVAP/AIR) that will come out, but you going to run the fuel pump unprotected? How are you going to eliminate the relay (for instance) without adding in more wiring to take it's place? Still have to wire it in so that you get ignition switched power, which is what the relay does, and fused at that.

    The alternator stuff will come out too, but the starting stuff isn't integral anyways, at least with TPI...I kept all my stock truck starter and alternator stuff, it just happened to run in the same wire loom as the EFI wiring.

    I'd be surprised if the TBI alternator or starter stuff goes in the passenger side of the truck.

    What else do you expect to cull from the harness??
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    ESC is going, that's useless for what I'm doing and it doesn't even set a code to run without it.

    EGR obviously.

    I'll have to look at the rest of the circuit before I can tell you, thus far I haven't got a diagram that I can read.

    Dorian, what you fail to realize is that there are rock crawlers out there running with nothing but a TPS and IAC to make their rigs run. Open loop all the time, no O2 sensor, no CTS, nothing. People pay big money for harnesses that are easy to plug and play.

    I wanted to get started today but my yard is way too soft to be moving dead trucks around, so it looks like I'm going to have to do something else.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Is ESC standalone on the TBI stuff, or does it have its own module?

    Now, switching attitudes, why the hell would you want to remove it? I guess if all you want is better ability to run off camber, then do away with it, but ease of startup is part of that system, eliminating that eliminates all the advantage TBI gives you for startup. :confused:
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    They can run whatever they want, and I understand that, but if the same people that are willing/need to change axleshafts or weld on the trail are afraid of a few strands of wire, or a couple of relays, I don't know what to say. It's fear of what is unknown, thats all there is to it.

    Just run mechanical diesel if all you want is simplicity, (and you know this) because every advantage of running TBI short of off-camber is removed when you start pulling everything you mention people do. Open loop, no CTS, no way to retard knock with bad gas, hard starts, all make for vehicles that may run, but needlessly wasting gas (Not talking about MPG, talking about amount of fun between fillups) and causing the same problems carbs are notorious for (CTS fixing a bunch of those for instance) seems like switching to TBI is about pointless.

    Seriously. Why do ALL that work of changing to TBI to save stalling a few times, if that is all you get out of the swap? Thats akin to changing to EFI to save a couple of MPG, which will never net what the swap cost.

    I can see it if a Q-jet stalls on you constantly off-road because of driving conditions, but I'm not thinking you have the nose up or down so much, so often, that a Q-jet causes problems constantly, enough to make the additional wiring (and components) worthwhile, if apparently all you are worried about is failure. Am I right or wrong?
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    My Q-jet runs good. I just want to have the ultimate in off camber performance. I'm going to run the CTS, IAC, TPS, 02, etc., and eliminate unnecessary components that add complication to this project. Beyond that, I have no real use for EFI, this is a trailered rig.

    As to a mechanical Diesel, I'd be running one if I had one. I do not.
     
  13. justinf

    justinf 1/2 ton status

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    I eliminated the fuel pump relay and associated oil pressure switch on my jeep when I wired in the TBI motor. I didn't want to have the relay turning off the fuel pump if I lost oil pressure. I can read a gauge and will shut it off if there is no oil pressure.
    Now, I have had the jeep leaned way the hell over on the side, zero oil pressure, I kept driving and as soon as the jeep got back a little more level, oil pressure returned. It would have pissed me off if the fuel pump would have cut out, and the engine died, causing me to have to pull cable to get out of the spot when I could have driven.

    I hooked my fuel pump up to switched 12V source, it is fused, and runs through an additional switch on the dash so I can turn off the pump even when the key is on.
     
  14. miniwally

    miniwally 1/2 ton status Premium Member

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    Tim, I have done a few of these swaps and you are making it way harder than it really needs to be. Remove the stock harness, this is easy until you get under the dash and have a few wires to trace and follow. Once removed you will find that the thing really only needs a ground and one twelfe volt wire hooked up to run. edit Don't forget the VSS stuff either in the speedo or the transfer case

    Call Howel or someone like that and have a chip burned that eliminates the egr and whatever else you want removed but LEAVE the wiring in the harness. It is eaiser.

    The extremly easy way to this is call Howel and get their harness and a chip. Easy two hour installation and you are gone. Just use the donor truck for the hard parts not the wiring.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    I can see removing the oil pressure switch for your reasoning, but again based solely on wiring, you've added another switch in which has at least as much wiring as the oil pressure switch itself had. I can't think of an instance why you'd want to shut the fuel pump off with anything other than the key, but perhaps there are reasons for that I don't understand.

    As for having it on the side with no oil pressure, I *certainly* can't imagine running like that. :) Something about KNOWING there is no oil going through the engine would stop me from getting in that situation. Again, thats personal preference, I just don't wheel that hard, where in your case, it sounds like a necessity.

    I understand reliability comes from simplicity, minus the oil pressure switch, I don't see a simpler/more reliable way to do it than GM did. Still fused, switched, and relayed. If I'm not mistaken, the fuel pump can draw enough to cause problems if the wiring for the pump is run through a switch, unless it's a monstrous switch. I recall reading something about this before, draw from a device being enough to cause problems with a switch in the circuit, which is why GM used a relay.
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    One 12 volt wire?

    ECM constant feed, fuel pump, injector feeds (I assumed one for each injector, and that is wrong according to below posted diagram :)), VSS needs one 12V ignition switched, what else am I missing?
     
    Last edited: Feb 8, 2005
  17. TJS

    TJS 1/2 ton status

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    I am going to "strip" a 89 c/k wire harness. I found this from thirdgen.org

    http://olympiafj60.home.comcast.net/TBI_wiring_diagrams.PDF

    Print this out before it goes away. I do not see how just one 12 v source. The way I read this schem. is you need fused (was ecmb fuse) fuel pump and then switched power for ECM input. I think there is another one as well. I did not really have a chance to study it. When I get the harness I will "section" it off. I should be getting my harness soon. I got it on e-bay. I hope it is not hacked up.
    T.J.
    www.tjsperformance.com
     
  18. miniwally

    miniwally 1/2 ton status Premium Member

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    I got a little ahead of myself with the one wire comment.
    If I remember correctly the minimum power is 1 ign hot, 1 constant hot and hot for the fuel pump. Every other device recieves its power from the fuel injection harness.
     
  19. jac6695

    jac6695 1/2 ton status

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    Whats the big deal with the fuel pump relay? Every high amp draw should have a relay in the circuit, and GM has a really nice, dependable relay built in to the harness. You can always splice in a manual switch if desired. The oil pressure switch seems to be misunderstood. It is meant as a backup to the relay- it is wired in parellel with the relay contacts, so if the relay fails, you can still drive the vehicle.

    This is one of many failsafe features GM used in there TBI systems. Another good reason for using the relay is that the fuel pump runs only when the ECM senses the distributor turning. That way, if you roll the truck, and a fuel line ruptures, the engine will most likely die, and the pump automatically shuts down. No need to hit a seperate switch.
     
  20. 84_Chevy_K10

    84_Chevy_K10 Banned

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    The problem with the fuel pump relay in my donor truck/harness is that there isn't one. The fuel pump in this truck is wired straight to the coil and has been since I got it. The fuel pump relay is M-I-A and I'm not putting it back. :grin:
     

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