FYI fellow helpers, original thread:
https://www.therangerstation.com/forums/index.php?threads/truck-will-not-start-or-starts-intermittently.210392/
Well that's progress, good solid cranking means you are past the battery or wiring connection mystery.
When it did run, right up until you started wrenching it ran fine right (ignore the starting, only talking about how it ran once started)?
and here is a list of everything you did (from the other thread):
(from post #10)
changed the ignition switch
(from post #21)
1. Changed Purge Valve
2. Removed Battery Cables and cleaned the post with a wire brush and baking soda. I did not open clamps and clean that I will try that in AM to be more complete.
3. Changed the Ignition Relay Switch under the dash
- same work already done as post #10, right?
4. Checked Post to Post Volts drop test etc...working on that list still.
(from post #22)
tightened up the steering column shifter
- fixing the park / neutral lockup switch. Solving the previous starting issue.
Have you done anything else?
Hook up and ODB2 and check for codes - is it throwing any code?
The basics, the very very 1896 basics... All engines require 3 things to run, Fuel Air and Fire.
So, we eliminate those 3 possible issues and then we hand it over to the computer gurus for modern computer wont let it start issues.
Air is kinda a given, there is almost nothing that will stop a vehicle from getting air - but check the air filter isn't 100% clogged or there isn't a piece of debris sitting across the intake completely choking it out. (even with air issues it will act like it wants to start catching once in a while - it sounds like yours cranks and that is it, not even catching).
Fire is an easy one - put a timing light on a cylinder spark plug wire, crank it and see if the light is flickering away - that typically means everything up to the spark plug is confirmed (not always, but it is a "good enough" test when the engine ran ok previously).. No flickering light = no spark signal... bad coil, distributor/electronic ignition module,
COMPUTER is stopping it, etc.
You could also pull a plug and check the condition - if they have the electrode completely melted off kinda disaster or totally covered in soot then yeah you wouldn't have spark.
Fuel is also easy on carb, but throttle body / direct are a bit harder as they are harder to get into the fuel system. On an old carb I would just unhook the fuel line at the carb, point it into a clean gallon jug and crank for a few seconds - confim it spurts away and shoots lots of fuel into the jug while cranking. Before tearing into anything hunting I would ask, does it throw any codes? (P0193 - fuel rail pressure sensor) The computer has a sensor for everything, and codes will save you unhooking and hooking tons of stuff diagnosing.
One question asked in the previous thread but I didn't catch an answer you hear the fuel pump running when you first turn the key to "on"/run. With electric fuel pumps they pressurize up the system to full pressure at this stage, before you even start cranking. They make a distinctive whine you can hear on any vehicle that's got em.