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K5 wiring

Jake_C_

Jake_C_

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Ok I’m starting this thread because I’m tearing into the wiring in my k5 and I’ll inevitably need help. Important to note this is an 88 but now with a carb and no emission stuff. I’m deleting everything I can as far as extra wires go. Here’s a list of things I know I need in the engine bay, help me if I’m forgetting something.

Wiring for starter
Wiring for alternator
Wiring for dizzy
Wiring for heater box and ac
Wire for oil sender
Wire for temp sender
Wiring for wiper motor
Wire for washer fluid pump
Wiring for headlights and markers.
Wiring for horn.

i think that’s it. Again let me know if I forgot anything. So my first question is, is this some sort of ecm:
26FEAD69-F8DA-4566-9636-F56E85ACF9F0.jpeg
this is under the dash right behind the glove box. Wires come out near the middle of the firewall. If so is it deleteable? My assumption is it went to the emission stuff.
 
What kind of transmission you have?
700r4 lock up converter wires go to what
th350 no electronics
th400 no electronics
I asked I'm in the same boat as you are except I've yet to pull any wires out yet.
I did the same as you
I terminated all the extra wiring at the bulk head that controlled smog pump, sensors O2 sensors etc etc
 
MEMO43 said:
What kind of transmission you have?
700r4 lock up converter wires go to what
th350 no electronics
th400 no electronics
I asked I'm in the same boat as you are except I've yet to pull any wires out yet.
I did the same as you
I terminated all the extra wiring at the bulk head that controlled smog pump, sensors O2 sensors etc etc
Click to expand...
Sm465 transmission so no wires besides reverse lights switch. Pretty sure I can get rid of all that stuff but I want to get confirmation from a couple guys first just to be safe.
 
Jake_C_ said:
Sm465 transmission so no wires besides reverse lights switch. Pretty sure I can get rid of all that stuff but I want to get confirmation from a couple guys first just to be safe.
Click to expand...
Yeah you're good.
I did that before on a diesel manual swap.
I will be doing the opposite on an 84 soon, putting the 89 tbi in it.
 
Wiring for the fuel pump. I believe that circuit runs through the computer (dependent on oil pressure too?).

I recently did a birds nest delete on the dash wiring on my 91. I deleted a good bit more than you, the project became overwhelming for me so I bought a modified/ simplified harness from a guy on FB that builds custom harnesses. The wiring mods are detailed in my build thread.

If you consider an aftermarket harness know this, while Painless labels their harnesses “customizable” they really aren’t. Painless will not add or deleted circuits by request beyond with / without A/C. They will suggest buying one of their premade kits with xx number of circuits and you just don’t use / tie up the extra wiring. Their kits are also universal length without connectors. I thought that level of diy plus being non customizable wasn’t worth the price. The harness I bought from Harnessworx was 1/2 the cost and totally plug & play.
 
The ecm signals the fuel pump relay, for 2 seconds after switching ign to on. This is enough to fire engine and have oil pressure switch provide the ground. Provide a switched ground to the relay and your good. The oil pressure circuit would be rendered ineffective, with manual switched ground.
 
@Wes Harden @nvrenuf i actually was going to ask about the fuel pump believe it or not. And I looked into painless too and was not happy with them either. So the computer turns the fuel pump relay on for 2 seconds, and the oil pressure switch (deleted) provides ground as long as there’s oil pressure? So if I went in and pulled every wire coming off the computer that didn’t go to the fuel pump or the oil pressure switch, would the computer still function? And I understand bypassing the oil switch by using a another ground but why does the ground have to be switched? I really appreciate the help guys.
 
I'm not sure what the point of no return is for the computer wiring vs losing those functions you want to keep.

When I got my 91 it had already been stripped of the TBI, A/C, etc and had a carb. With the computer unplugged my starter and alternator worked as did all of the steering column related controls (wipers, ignition switch, turn signals - cruise control was gone), horn, courtesy, radio. Exterior lights, brake lights and hazards seem to be stand alone system(s) from the computer. I don't know about the ignition though, mine has a stand alone set up but if you used an early HEI distributor you'd only need a switched 12v ignition source to run it.
 
nvrenuf said:
I'm not sure what the point of no return is for the computer wiring vs losing those functions you want to keep.

When I got my 91 it had already been stripped of the TBI, A/C, etc and had a carb. With the computer unplugged my starter and alternator worked as did all of the steering column related controls (wipers, ignition switch, turn signals - cruise control was gone), horn, courtesy, radio. Exterior lights, brake lights and hazards seem to be stand alone system(s) from the computer. I don't know about the ignition though, mine has a stand alone set up but if you used an early HEI distributor you'd only need a switched 12v ignition source to run it.
Click to expand...
Yeah I got a HEI dizzy, I assume it gets power when you crank and not with the first click of the key. Seems like I could just hot wire the fuel pump to only run when the vehicle is cranking and running, same as the dizzy. It would take a little longer to fire up but I don’t see that as a big problem. Is my reasoning correct here?
 
The computer doesn't provide power to the various components it controls, only a ground. If you provide a ground but do not switch the ground your fuel pump will run continuously. I wouldn't attempt to use the computer for your fuel pump control circuit. Either use what is there and switch a ground to the current fuel pump relay. Or redo the whole fuel pump circuit with switched power from ignition switch.
 
I’ll probably do the latter. That way I can remove the computer and all wiring for it. Thanks a ton for the help man.
 
Jake_C_ said:
Yeah I got a HEI dizzy, I assume it gets power when you crank and not with the first click of the key. Seems like I could just hot wire the fuel pump to only run when the vehicle is cranking and running, same as the dizzy. It would take a little longer to fire up but I don’t see that as a big problem. Is my reasoning correct here?
Click to expand...

No non computerized HEI need 12v key on. I run my pre HEI converted engines with a relay, from the existing positive coil wire @ 9 volts. Your ign positive wire in the existing loom should be 12volts. I would use that.
 
Mine is similar to what Wes described, 12v key on signals to both (pump & dist) with a relay in my pump circuit. I don’t notice any delay in cranking.
 
nvrenuf said:
Mine is similar to what Wes described, 12v key on signals to both (pump & dist) with a relay in my pump circuit. I don’t notice any delay in cranking.
Click to expand...
Perfect, that’s what I’ll do then. Much thanks.
 
Also, to eliminate 100 piggybacks / splices from the factory fuse box I added a Blue Sea brand auxiliary fuse panel. The panel is split in half so I ran constant 12v to one side and key on 12v to the other side, each side has 6 available slots to wire devices from.
 
nvrenuf said:
Also, to eliminate 100 piggybacks / splices from the factory fuse box I added a Blue Sea brand auxiliary fuse panel. The panel is split in half so I ran constant 12v to one side and key on 12v to the other side, each side has 6 available slots to wire devices from.
Click to expand...
I’ll look into that, thanks!
 
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