Need help troubleshooting electrical problem

[stock75]

Hello everyone, haven’t posted in a long time but that hasn’t stopped me from combing the forums any time I have a question or problem. After spending some time searching to no avail I was hoping you could help me diagnose my problem. Vehicle is a 84 jimmy. Fairly sure this came stock with a 305 but was swapped to the 350 at some point before I got it. I was going to a relaxing drive with my dog a couple nights ago and all was well then all of the sudden I lost all throttle response and heard an extremely large backfire. I was able to coast into a parking lot luckily. Once I got to a safe place to trouble shoot (vehicle was still running) I came to a complete stop, found neutral and tried revving it up to clear it out as before this happened I had been idling while taking a phone call and when I’m out wheeling it has been known to load up from time to time. So I tried revving it up and got absolutely nothing, it was still running but just barely. So I turned the ignition off and popped the hood to see if anything obvious was wrong. Everything looked fine so I moved to the fuses, I happened to have a volt meter on me and checked all the fuses for continuity, all of the fuses were fine. At this point I tried starting it up again. Turned the key and got absolutely nothing. Checked all the wires going to the starter as well as just an overall quick wire check. Everything seemed fine so I tried having someone jump me. Even with the other vehicle hooked up via jumpers I got absolutely nothing when turning the key. I got towed home and it sat for a couple days until I had time to work on it. So today i did some voltage checks and more continuity checks in various wires, everything seems fine. I have voltage on the wires going to the starter which leads me to believe it might be something with the ignition. The headlights,, tail lights, and dome light seem to be the only circuits that are functioning. While I have a solid 12 volts at the starter terminals it will not even attempt to crank. None of the gauges do anything when I turn the key to the on or acc position either. Also the blower motor is not working at all. I am a high voltage lineman by trade but when it comes to these car circuits I’m like a fish out of water. So where should I start as far as trouble shooting goes? I also found it weird that while I am getting voltage to the wires where they connect to the starter, the bulk head on the firewall is not giving me any reading. Thanks In advance for any input!
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[Just call me Sean]

I would check the fusible links.

[AJC]

Originally Posted by Just call me Sean

I would check the fusible links.

I think he is right about the fusible link. Its most likely to be "Red-2 Thermo HW" or "Red-2A Thermo HW". The "Red-2H Thermo HW" goes to the alternator, CTSY fuse, Horn-Dim fuse and the light switch.

Also here is the thread to get the service and wiring manuals to help out in the future. PDF of Square Schematics & GM Training Manuals

[Dead Parrot]

2nd on the fusible links. If you find a bad link, you need to chase down the bare wire or shorted device that caused it to blow or you risk a repeat. Much like having to remove that tree that cause the line power to go down before you call the job done.

BUT, double check that you have gas at the carb. Possible you had multiple failures at the same time. Rotted suction lines can cause your initial problems with loss of power and backfiring.

Also, since the starter has voltage, possible the starter brushes picked that moment to die. Thump the front end of the starter with a rubber mallet. That will sometime cause a set of worn brushes to make contact for a few more starts. If this works, plan on replacing either the starter or brushes fairly soon. This has the virtue of being a quick and cheap test.

[Ziegelsteinfaust]

My 74 had similar issues, and the column slider ended up being the culprit.

After cleaning up the electrical, and fixing every other issue my truck had. Still with no success. A auto electrician I took it too fixed the issue for me.

[stock75]

Thank you for all the replies! I replaced the fusible links going to the bulkhead(correct term?) on the firewall, was working on getting the one down on the starter wire done when I noticed some corrosion and cracks on the solenoid. Went to pull the starter off to inspect and ended up dropping it and busting the end of the solenoid. So I went to the parts store again and got a new one then ran out of daylight. Ill get that last fusible link replaced tomorrow and get the new starter installed and see what it does. I was able to chase down to bare spots on the wires running to the starter so I shrink tubed those, really hoping once I get it all put back together she starts. The previous owner had a viper alarm, sub bar stereo harness AND a breathalizer so the wiring has been a bit of a mess as you can imagine.