Switch panel setup

I want to just wire up a basic switch panel. I’m working on a 240sx and have removed all the OE wiring. I want to have fuel, starter, charging system, lights, signal lights, and power EFI. My problem is I’m completely lost on how I should be setting everything up. So far I’ve only come up with this. I have the OE wiring diagram and it’s like trying to read German. Can someone please help me figure out how I can wire everything up without frying my car.

I'm preparing to start the same project on my Chevy Powered Mustang.

You're going to want to make sure you have an understanding of how much of a load each circuit will carry. You don't want to use too small of a gauge wire on a high demand circuit (think starting and charging circuits).

Which ECU are you using for your EFI? If it is aftermarket they should have documentation available showing what size wire, fuses, and relay placement they recommend. I'm using MegaSquirt3, you may be able to use their wiring diagram as a starting point.

If you're using the OE ECU, you may need to jump through some hoops in order to make it to operate as expected. I'm not familiar with the 240s, but it may require some inputs that are easy to overlook (for example, Park/Neutral switch may be required for the ECU to start the car, impact sensors, brake switch, etc). These types of things MAY be apparent by looking at the wiring diagram, they may not.

What I plan to do is print out the OE wiring diagrams, buy a pack of multi colored highlighters, and highlight all of the circuits I'll be using (lights and body control, EFI is aftermarket and not related to OE wiring in my situation). You can then use that to duplicate what the OE did, without including any unnecessary circuits. I'll be adding in my own relay board and fuse box, strictly for cosmetics and ease of installation.

Be sure to clearly document everything that you do. Even if you expect to revise the harness, write down what you've done, and make note of the changes. You may find that your original setup was better,correct, or more convenient. Having the original setup documented will help you revert back to previous setups much easier. But most importantly, it's imperative that you have documentation when you try to diagnose an issue.