This last year, I gave my stepson my 1997 Dodge Dakota (3.9L auto) to use. When he left it back off, it had appeared that he jumped it, as idler arms, end links, tie rods, and ball joints were either bent, broke, or missing. I proceeded to spend a lot of money on an old, very rusted truck. It had always been dependable and ran like a champ.
When working underneath, I noticed a coolant leak dripping down from the timing chain cover. I proceeded to tear down the entire front of the engine to replace the timing cover gasket. Just for good measure, I replaced the water pump as well. By the time I assembled everything, I also replaced every belt and hose under the hood (I had replaced the radiator in 2019).
After I reassembled everything, it ran so smoothly and quietly (I had already replaced the exhaust manifold gaskets before I loaned it to my stepson).
I figured since I was fixing everything, I might as well charge up the AC. I got out my manifold gauges and hooked up my 134 tank. The weather was a little cold, and the A/C was not kicking on, so I decided to jumper the A/C relay.
***Note, this is where things went horribly wrong.****
I had forgotten that the diagram on the power distribution relay was inverted, and I jumpered something else, and the engine died. Luckily, I restarted it, and it ran for a bit. In the span of about 5 minutes, the idle went erratic, then rough, and rougher, until it finally died.
I checked my coil and had 12v on the green/orange, but no spark at the coil. I threw a new coil at it, but I ended up figuring out I had no activation signal. I checked my crankshaft position sensor and my camshaft position sensor. They both tested fine.
As a last resort, I ordered a new ECU. I installed that today, and it started as soon as I hit the key. I was sitting at the wheel when after idling smoothly for about 10 minutes, the engine shut off. I hit the key again, and it immediately fired off. It ran long enough for hot air to start coming out of the defroster when it shut off again. No rough idle, no sputtering, just off like I hit the key. It has not started since. I have the battery charger running (it was at 11.9 volts on the new battery I bought last year).
I rechecked the coil, and I have no spark. I need some help here. All I want to do is get this truck sold to someone who needs a good running vehicle. If I had not stuck so much cash into it in the last 10 months, I would have sold it to the local pick and pull, but I am too far into this truck to drag it to the salvage yard.

 

Are you still getting power to the coil? Keep in mind, it will only have power for about 3 seconds if the PCM doesn't see the engine turning.

 

As HeyYou said, you should have 12 volts at the coil for about 3 seconds at key-up. When the engine is spinning, you should have constant 12 volts on one wire, and a pulsed ground from the PCM on the other.

The diagram i found for a 97, headlamps and AC relays are next to eachother. Jumpering the headlamp relay shouldn't have broken anything besides a fuse.

 

I know. It makes no sense. Why would it run fine for a few minutes on a new computer, the sputter and die again.
What should have been a blown fuse at most, I have crank and no fire again.
Video of cranking with voltage on the green/orange wire.
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