I continued working on the wiring this weekend.
The I-Squared was having some trouble with my fan. Seems that the initial current draw for the electric fan was too high for the I-Squared. One option would be to dedicate two separate circuits to the fan. Another would be to build some kind of inrush limiter circuit, either a fancy active circuit or an inrush limiting thermistor. But in the end, the simplest thing was to just buy a $35 fan control module from AutoZone and skip the I-Squared on this circuit. I got it mostly wired up. The fan operates thermostatically with a probe in the radiator. I also have an override switch to turn it on, and there's one more wire I need to connect so that the A/C also turns it on.
Then I turned my attention to the EFI harness. I spent a long time tracing and labeling the wires on the three connectors that go to the Mustang body harness. Those have things like the gauge wires and power inputs on them. I nearly drove myself nuts with a light green/purple wire that came off one of these and just seemed to go nowhere. Finally traced it to a plug labeled "To Heater". I still don't know what it is, but I know where it goes.
I removed the EEC power relay from the harness. I'm running my power from the I-Squared, so there was no need for this relay. But I decided I do still want a fuel pump relay so that the computer can control the fuel pump. I also decided to put the inertia switch directly on the fuel pump circuit instead of on the I-Squared control circuit. If I crash and that switch opens, I want the fuel pump off no matter what. So I found a spot near the fuel filler to mount the relay and switch, and I'll make an access panel from the trunk area.
I'd have finished up the EFI wiring yesterday, but I took most of the day off from the car because it was Stephanie's birthday. So I still have a few connections to make and wires to run, but it should all come together soon.
[This post should have been published 3/3, but Blogger was crashing on me.]