1987 R1500 V8 TBI M/T Electrical Issues

First post, Howdy!
Small background, 10 years avionics tech, now avionics/electrical aircraft engineer, spent a stint as a Ford Tech, got all sorts of training there, tinkered and worked on too many vehicles to count.

Okay, down to business.

1987 R1500, was given to me, didnt run, but would turn over, replaced...entire.. fuel system, ran like a top after that.
Drove it about and parked it for, oh a couple months.
Went out to the truck, started it up, idled for a few minutes.
Died. No start, no gauges moving.

Went out recently to diagnose it now that its warmer.
Battery voltage good.
Power available at bulkhead terminal block and both sides of fusible link.
Power and ground check good at ignition switch.
I assumed it was the switch then, replaced switch.
Nothing.

What does work?
Horn, and Headlights on full-on. No highbeams, dome light didnt work before, and I dont remember a buzzer working, either way, they arent working now.

Fuses check good.

I HAVENT checked for power at the ECM, but I figured moot because something just simply isnt getting power.

I figure I will change the entire fusible link wire segment next, from TB on bulkhead to starter, but reading the schematic, it appears that if that block and the ign-sw are getting source voltage, then "something" should turn on.

Please help me, I missed something somewhere.
I have the factory wiring diagram, but my goodness its a hard read, even for me, and I draw schematics for aircraft.

I have perused the search function and all over the internet.
Unfortunately the 1987 TBI R1500 seems to be very unique in its wiring during my interweb searches.

Sounds like 'Ground Gremlins'.

Check the ground from batt to block, batt to frame and batt to body.
Then there is a ground block on the upper left kickpanel.

These seem to be the things that create most electrical headaches.

https://www.gmsquarebody.com/forums/the-squarebody-reference-library.52/

Wiring and service manuals can be found here.

Snoots said:

Sounds like 'Ground Gremlins'.

Check the ground from batt to block, batt to frame and batt to body.
Then there is a ground block on the upper left kickpanel.

These seem to be the things that create most electrical headaches.

Click to expand...

I checked the battery to block (alternator specifically) and battery to frame.
I will look for this kickpanel ground block and give it a check.
Thank you

So I took a look while i was at work at this Factory wiring manual again.
It finally clicked how they drew this, and how to read it.

Im going to make my own t/s print, and share it when complete for power and ground distribution in relation to IGN sw.

Have you checked continuity for the ignition switch itself?

you can hook one lead to your firewall junction and one to your pink ignition wire. Should sound off in both ‘run’ and ‘crank’ positions.

isn't there a "no start" trouble shooting guide in one of the service manuals in the reference library. I would start there. highdesertranger