84 K5 build... converting to tbi

[caliphatman8123]

Just a question... does anyone have a wiring diagram for a stand alone tbi for the 5.7L... just not sure where to start and I'm very limited on funds so I'm thinking I might try to make the harness myself... besides then I can take credit or blame for it working or not working... lol

[dave w]

What year / vehicle / engine TBI wiring harness are you going to use to build a stand alone harness? Knowing which wires are, battery +, Battery -, ignition switch on / start, and crank input for the computer is a good place to start. Knowing what year / vehicle / engine the donor TBI harness really helps!

There are several ways to build a standalone harness, converting a used harness is usually the lowest cost way to go about building a standalone harness. Soldering wires and connectors will save money. Butt splices, will cause problems in the long run! I've done precise electrical measurements on soldered wires vs. butt spliced wires. One butt splice in the middle of 5 feet of 16 AWG wire is equal to about in 4 soldered wires to make 5 feet of 16 AWG wire length!!! There are several wire colors that are used for more than one function. There are several wires in the harness that have nothing to do with the TBI! There are likely some wires that will need to be added to the harness, ALDL connector and Service Engine Soon light are a couple I can think of. Quite often wire lengths will have be changed, longer or shorter.

dave w

[PJG1173]

I used the wire diagrams in the ecu info threads to build my harness. Ditto on using solder and heat shrink vs butt connectors. It took me about a week to build my harness working on it about 2 hours a night. Having a label maker will also be a huge help keeping the same colored wires mentioned above organized.

[caliphatman8123]

Well I have both the wiring harness from the 84 K5 off and the wiring harness from my donor 87 5.7 tbi engine off and gonna see where that takes me... lol

[dave w]

Well I have both the wiring harness from the 84 K5 off and the wiring harness from my donor 87 5.7 tbi engine off and gonna see where that takes me... lol

I use a full size sheet of plywood held up by saw horses to make a temporary table to organize the wiring. Label everything! I put a complete TBI intake / EFI system on the table and start hooking things up.

dave w

[caliphatman8123]

This wiring is driving me nuts... from what I can tell I need to splice in the altenater, a/c and started wiring... that will be the easy part... its making the efi and making sure the gauges work properly and the ALDL works

[dyeager535]

Assuming this wiring is for the CS series alternator, I would advise dumping the older SI series and going with the CS. Normally it's output is much higher than the SI, and in my case, is much better at keeping up with electrical load at idle.

Not sure what starter wiring would need spliced, GM used the same starter setups throughout AFAIK.

[caliphatman8123]

ok if the efi harness off the donor connects to all the sensors and all that already works... then all I should have to do is figure out how to wire in that harness to the fuse block that plugs into the outside part of the firewall of truck... right??? basically connecting all power wires and grounds... I really wish I had a blown up view of the wiring that went to each of those plugs to compare... although the more I read and the more I stare at these harnesses the less scared I'm becoming... once the fear is gone I guess it will be an F' it moment and jump in... worst case senerio i screw it up and have to start over

[dave w]

The old EFI harness will need it's power (ignition on/start power, battery "+" power, and grounds like you describe. The old EFI harness will also need a wire connected to the "S" terminal of the starter motor.

Usually the ORANGE wire on the old EFI harness is Battery "+".
Usually the Pink wire with a Black Stripe is the Ignition Switch On/Start Power.
Usually the Black wire with a White Stripe is the Ground / Battery "-".

dave w

[dyeager535]

The '84 truck fuse panel, does it have all the "auxillary" terminals along the top, or are they still kind of randomly scattered around the panel? These are the single connector terminals, that have things like your rear power window hooked up to them, these are not the empty fuse slots.

Either way, you really only need to use two of those to power the EFI stuff (edit: not true, you only need ignition switched. If you add fuse panel underhood, run wire directly from battery to it)...ignition 12V, and battery 12V. This is what I initially used to "get around" the limitations of the older fuse panel, without having to hack it up: http://www.ebay.com/itm/ATC-ATO-6-wa...24b9cf&vxp=mtr Each of the auxillary terminals on the fuse panel is protected by a 30A breaker, but obviously you use the ebay-linked fuse block to properly fuse each EFI lead (ECM, injectors, etc). You really aren't going to want to try and use the engine side of the firewall connector to run this stuff, there are empty terminals, but it's just easier to run it under the dash over to the passenger side, and out through the heater or ESC grommet if you need to.

If you want something a bit more adaptable, on the ~early 90's Cadillacs they have a mini fuse terminal (actually the cars had three of them, one with just fuses, one with about 10 fuses and 2 relays, and another one I didn't look closely at) which could be used under-hood to do the same thing. The trucks have huge wasted areas on the firewall in the engine bay, normally with lots of bolts and holes, which makes mounting easy for something like this. Initially I wired the above linked fuse block in the cab, as it was close to the fuse panel, but have since changed over to the Cadillac one. The advantage to using the Cadillac fuse panel is that you can power multiple fuses off of ignition 12V, or battery, or however, instead of needing a separate 12V feed for EVERY fuse, which kind of makes the ebay linked one a mess when you start dealing with 6 fuses/12 wires.

If you start getting into other components like extra lights, headlight relay mod, electric fans (a waste on a truck unless you absolutely need them IMO) then you will start to see the advantage of going with a later fuse/relay center underhood...they are more compact than mounting the fuel pump relay in one place, the fan relay somewhere else, and the additional relay(s) to power the igntion 12V fuses themselves. This greatly cleans up wiring.

If you are locating the ECM behind the glove box, it also makes for shorter runs of wire to the ECM.

I hope this makes sense.

[caliphatman8123]

Another day stuck at work... its been to long to not be working on the K5... between work and making time for my family this project is taking way to long... I'm just itching to drive my truck... OK done with my rant... venting done back to work at work instead of on my K5... this sucks

[jameslleary]

I really wish i could get down there and help. 3.5 hours is a stretch.

[caliphatman8123]

Well update time... Wiring harness almost completed... Ty Jim for all the hard Dork you've put into this... I really appreciate it all

[EagleMark]

I hope that's a spell check issue and your not commenting on Jims hard dork?

[caliphatman8123]

Yes that's a spell check issue... Lol not commenting on his Dork... Lol his work he put in on my harness is amazing it looks great and he made it the way I wanted to so it all along...