With a little trial and error and help from Gemini, I think I've narrowed it down to the ignition coil. They're not terribly expensive so I was thinking to just replace the whole thing.
I'll looks like I must have an internal resistor. But I'm not sure about the igniter asst. That's on top. Should I replace it too, or is there something that is all in one?
I am going to remove it and test it tomorrow.
But I'm also still probably going to get a reduced gear starter.
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If you've already identified some potential electrical/wiring issues with your harness, before replacing components, I'd at a minimum, clean up any and all ignition connections and trace out your critical ignition circuit to carefully make sure you have proper voltages at key places (switch on only, then cranking at coil + at a minimum). If it was running well before, it's likely not a component issue keeping it from running now.
Having said that, I found the FSM very helpful in many aspects of getting my 79 running, including voltage verification mentioned above, and individual component tests (ignition switch, coil, igniter, distributor pickup, etc.).
Even before that, I would highly recommend doing searches on this site to get a feel for the the symptoms and systems you'll be investigating. That proved hugely useful in starting my journey. And, not sure I would follow too much advice from AI without confirming it here. Some of the FJ40's systems are unique and specific.
Oh, and as an FYI, if you're running a stock 79 electronic ignition as suggested by your pics, you may have a pink, inline resistor wire (Yazaki) between your ignition switch and coil that helps to drop the voltage at coil + to 7v when running down the road.
You may want to check out some of the discoveries found in a couple if my old threads while bringing to get my 79 back to life. First, correcting cobbled wiring (see
@Coolerman wiring diagrams) and cleaning rusted grounds got me a baseline. Then, using the FSM, I was eventually able to verify a bad distributor pickup, a failing igniter and a sloppy distributor shaft. Once identified, I opted to upgrade to a FJ60 ignition system (igniter, coil, large-cap distributor, resistor wire delete).
But, before assuming you have bad components and start replacing them, please do some basic stuff first. The wiring diagrams and FSM are your friends. It may take a little while to absorb, but you'll have a much better understanding of your rig and the tools available to maintain it.