Could use some diagnostics help

Used a standard automotive type of relay and socket and mounted it on the firewall.  Tapped +12V off of the power side of the starter solenoid & blended wire routing to the relay.

Here is the schematic:

I made a jumper wire to the unused key on male terminal in the fuse box it's actually +.1 volts compared to the battery when running and used that. Did not start. Plugged it back into the original spot starts. 

Note. That .1 volt is at 13.5 running.

 Even Edison discovered thousands of ways not to build a lightbulb. 😆

I did find something out about the plug. The aftermarket bullet connector apparently makes poor contact inside that plug. I moved the harness and it skipped a beat. I don't know if a hard splice solves the problem but it is another discovery.

Also bypassed the fuel tank with a gas can to the pump. It's not the gas. Another one down. 😆

I haven't gotten to the carb. It's not running rich and I haven't excused the ignition just yet. I don't have a spare module so I may pick one up for sh*ts and giggles.

I hope that you get it fixed quickly now that you have a good idea of where the issue was.

That reminds me of the resistance in newer cars now that everyone is used to spark plugs that don't get changed for 100k miles. People regularly now don't change them at all, and well the vehicle, so the 2nd or 3rd owner has to figure out how old the plugs are. When you let the plug gaps reach never before sizes such as .150", guess what that resistance does? I had read of it, but I had my first experience of it with my last SUV, three years ago.

The coil pack on my 98 Explorer failed(hard miss on two cylinders). I had the truck for a month and first replaced the front suspension(4 bad BJ's). I worked on fluids and planned to do the plugs and wires soon. I needed the truck for work quickly and drove it as soon as I had checked fluids etc, but not the plugs. It ran fine for about four days, and then a miss began. I changed four plugs first, before work the next day. Four are very tough to get at without removing the inner fender cover. So I did the other four after work, but the miss had gotten worse through the day, and the other plugs didn't fix it. The next day I swapped coil packs, it has two, it's a batch fire waste ignition system. I changed the one that handled the two cylinders miss firing(CEL codes like P0301 and P0306), which fixed the miss. I threw that coil pack in scrap, and the other I saved as a spare). The gaps were all in the 0.135" to 0.160" range, way too high of course. The OEM coil packs are very reliable and powerful, but they will die with gaps that large.

The lights (sometimes referred to as "idiot lights") are just that, marginally useful and the circuits are basic - if that much.  I've found that a lot of the times this happens when electronic regulators are used (versus mechanical relay type).  

Should you find that you have this condition, it's an easy fix that will cost you a buck or so to remedy.  All you need to do is splice in a diode (sometimes called a rectifier) that will stop any bleed-back current to the "I" terminal of the alternator regulator.

Diode can be purchased from any electronic parts stores, Digi-Key, Mouser, Allied, etc.  Diode part number, such as 1N4004, 1N4005, 1N5402. etc. will work just fine.

This is the schematic and directions to add a diode:

Among other things, spent 21 years in avionics performing FAA interference testing of avionics equipment...also, thermal, humidity, vibration, over/undervoltage, lightening, RF radiated/conducted emissions and susceptibility, Highly Accelerated Life Testing (HALT), Blah-Blah-Blah.  And, 12 years in airborne counter-warfare equipment production & testing.

PS: LED lights can fire at voltages as low as 3.0V.

Did you replace the existing filament bulbs with LED that included a separate dimmer circuit?

If so, low voltages and spikes sometimes confuses the dimmer circuit.

Here's an interesting scenerio for you. I replaced the gauge lights with green LED bulbs. I used an incandescent bulb for the heater controls. They were too bright and distracting at night.

Anyway. With the incandescent bulb the LED bulbs are now dimmable.

Here's the deal: some LEDs are dimmable, and others are not. (Notice this when you're trying to buy LED bulbs for your house).

One of the characteristics of LEDs is that they inherently have a much narrower voltage vs. brightness graph as compared to incandescent lights.  In fact, if you have ever played with a home dimmer switch that is connected to incandescent lights, you'll notice that as you turn the brightness up from off position the lamp will light at a specific point, but after it lights you can turn the brightness control lower than the point that it lit up. (The filament changes resistance from heat).

It sounds like that the filament bulb(s) are giving you a little more voltage/current adjustment than with the LEDs alone.

Most LED dimmer controls produce a constant voltage but varies the on-to-off time (called duty cycle).  Instead of a direct current (DC), it produces a 0 to a fixed voltage square wave. The dimmer circuit varies the pulse width from no pulse width (0 duty cycle) to full on (100% duty cycle).

Notice with some of the early cars with crude LED control. At night, turn your head while looking away from the taillights, and it looks like a strobe light.