Starting from scratch, no wires on the engine. What would you do?

[trout]

So I have two wire harnesses laying on the floor of my garage, and a computer on my passenger seat.
The only wires reinstalled have been the ones to the transmission and oil pressure switch that get plugged into the engine harness, as are the rear window washer wires/hose.
Everything is factory on the harness, the bypass was done but the harness was left alone.
Coil, cap, and rotor already upgraded. I have a Motorcraft carb from Gronk with the electric choke.

What would you do from here for the cleanest and easiest setup?


Obviously avoid putting the computer harness back in. Looking at it I realized something has to be rewired to bring the ignition module back to life but the only post I can find about it only says, "there is a yellow wire that runs to 3 or 4 wires spliced together that needs to be hooked up to the ignition box if you remove all the wiring." And I have a lot of yellow wires. Is it really this simple that I just need to run one wire back to the module?


Also, are there any wires that can be removed from the engine harness?
It looks like I have one wire that ends up around the carb, with two wires going into one round plug that may have been for the original carb? I also have a few others I haven't been able to identify yet.

[trout]

I think my confusion on hooking the ICM back up is that I only need to use 4 of the wires coming out of it?

The other two wires, red and white, are they just power and ground?

[lapoltba]

I believe I am in the same boat as you.  I want to remove my computer and the associated wiring harness, but it appears that the ignition module is powered through the computer.  I believe it is just keyed off the ignition but I haven't been able to figure it out from the wiring diagram. 

I searched as you did and couldn't come up with a good answer.  My solution was going to be to find a junk computer and wiring harness for the connectors and make a jumper, then trace wires back from un-needed sensors and cut.

If you find any relevant information please post it.

[BenM]

You need all six. In the 4-connector, two go to the hall-effect sensor, one grounds to the distributor, one goes to the coil negative. In the two connector there is both keyed ignition and keyed start. We have a number of threads on it, check the search.

If you're using the stock intake, it's not much to hook up the oil pressure switch that controls the electric choke and pre-heater under the carb, if you haven't removed the wiring it's still there.

There is also a solenoid power wire for the sol-vac. It will be energized by use of either the intake manifold heater, air conditioning or rear window defogger through a diode pack in the wiring harness. It increases idle to 900 RPM so your lights don't dim when you come to a stop.

[trout]

I did search for other threads and found a lot, some of which was conflicting. But given what the majority said I have an idea but not 100% sure which is why I was asking. Also all the threads I find deal with the computer harness still being in the vehicle. I know what wires I would need to splice into on the computer harness to do the bypass.

I'm gonna spend tomorrow ripping apart the computer harness from my parts car, it's already butchered. I'll post what I find.

[trout]

Well a few more days of searching and pulling through my old harness. Old harness was too badly chopped up already to really be of much use. Started piecing the information together, best thread I found was one where jim seemed to be talking to himself. Guess the other side of the conversation had their posts purged, probably what happened to a lot of the info we need.

but it appears that the ignition module is powered through the computer.  I believe it is just keyed off the ignition but I haven't been able to figure it out from the wiring diagram. 

If you find any relevant information please post it.

It was, and it is. Here's what I found. Green wire that goes to the coil - is run through the harness as well, just gotta run that one directly.

Red and white also go through the harness. Red is the main power, I read conflicting information as to whether or not it is supposed to get full 12v though. The white is a starting circuit in the ICM that needs 12v when starting.

I got it all working by after doing the normal bypass and running the coil - directly, I ran the white wire to the top post of starter solenoid on the battery side and connected it with a ring terminal. Likewise I ran the red to the other side, giving it 7.65v. It started, and began to run before I realized my timing is too far off and I shut it down.

[BenM]

The ICM should get the full 12v on the red wire at all times, but the coil only gets that at start.

There should be a bypass wire from the solenoid terminal to the coil. The solenoid terminal is labeled "I" for "ignition". It's a separate relay contact that gets energized when the starter is active so that the coil doesn't feed back through the ignition module and cause problems. That should also be built into the main (not computer) harness.

So far, so good, eh?

[trout]

So far. Thought I could just leave the resistor wire there to avoid chopping anything up but since I need 12v for my petronix coil anyways looks like I will have to cut it out. Maybe I can reuse the connector to keep it looking nice. Hopefully part of the timing problem was the lack of voltage to the ICM. I'm going to verify that my timing marks line up because I was pretty sure I got the distributor set with #1 @ 8 degrees.

[trout]

lapoltba,

the last wire from the computer harness that we need is the yellow 12v ignition lead.
Here's how I wired it, excuse the crummy cell phone pic. The connector I stole from the already chopped up harness of my parts car. I then ran it with a ring terminal to the top post where I already had the red wire from the ICM going. Connecting this pin of the terminal and the red wire from the ICM gave both the ICM and the coil 12v.

Starts, runs, and idles right now @ 750 rpm w/ 10 degree timing.


Still got a lot of unconnected wires on the engine harness though.

[trout]