I have not updated this thread in a long time.
After the Michigan trip last year, the Scrambler was running fine. Went wheeling in December of 2017, no problems until late in the afternoon. I was on an easy dirt trail and the Scrambler cut off, just like you turned the key off. Towed it out the woods, did some checking, no injector pulse, no fire at plugs. Swapped out the coil and the HEI, no go. I was about an hour from home, got a buddy to load it up on a trailer and bring it back to my house.
I did a bunch of diagnostics, changed some more parts (the entire distributor, including pick up coil, another HEI, spare computer), it still would not run. Its been awhile, but I ended up jumping a hot wire from one of the HEI tabs to the coil (I THINK, BEEN AWHILE), hit the key, it started up. I'm a bit fuzzy on exactly what I did, it has been awhile.
I could not get it to repeat the problem, I drove it all year, no issue. It has been working fine until this past Saturday, it died at the end of my driveway, just like you turned the key off. Same thing, no injector pulse, no fire at spark plugs. The coil was getting 12 volts on the positive side, with key "ON" and "START". Jiggled a bunch of wires, still nothing. I don't think this had anything to do with it, but I left key ON, turned on headlights and heater fan, turned key to START, it fired up. It ran for 10 seconds, then shut down. Tried the headlight/fan thing again, no go. Under the hood, I checked/pulled all the TBI harness fuses, they were all good. Talked to the neighbor for a few minutes, shut the hood, was about to walk to the house, decided to hit the key one more time, it fired right up. Reversed it up the driveway and parked it. I started it up and turned it off 20 times, every time started up.
I wiggled most of the wires with it running, thinking I have a loose connection somewhere, I can't find anything. Drove it to work today, with a tow strap on the front seat, ran fine.
When I was messing with it yesterday, I went back and messed with the TBI harness fuse holder. The Scrambler sat in the shade all day, and had not been started, so everything was cool. After only running for 30 seconds, the fuse holder was very warm, and the fuse at the battery connection was hot.
Picture of fuse holder:
The 20 amp fuse is where the battery wire goes into it, supplying voltage. I can't remember what the other three fuses control, would have to trace the wires.
Picture of the back side of the fuse holder:
The only reason I noticed the fuse holder was getting hot was because I unscrewed it from the firewall. I wanted to inspect the wires for damage, and jiggle them to see if I could get the Scrambler to die. I changed the 20 amp fuse for a 15 amp fuse, and the thing is not getting hot anymore. But, I jiggled all the wires, could not get it to die, have the same voltage coming in/out of all fuses.
I am "thinking", IIRC, when the engine spins when you turn the key to START, the pick up coil starts to spin, sends signal to the HEI, which then sends signal to the negative side of coil to fire, which also sends signal to computer to pulse injectors. Maybe my problem is somewhere in these wires/connectors
EDIT - Forgot I started a thread on this toward the beginning of the year when I first had the problem:
https://www.cj-8.com/threads/gm-350-tbi-no-spark-no-fuel-injector-pulse.48539/