Done a lot of searches and seems I'm not the only C1500 owner with this issue. Hoping someone can help before I spend $100 an hour for weeks on end trying to diagnos this.
So, truck started cranking one day and then next day it wouldn't.
Replaced entire fuel pump assemply and filter.
Cranked and ran great. next day just spins but won't crank.
Replaced fuel pump fuse and relay.
Voila! that's it cranks and run great.
Next day spins, no crank
Replace ignition module, rotor, cap and coil.
Cranks, runs great........... next day spin no crank.

I'm not a mechanic but did try spraying started fluid in TBI and checked for spark. I DON"T believe when it just spins it's not getting fuel or spark.
Only thing old on truck now is the Distributor and ECM.
Oh, it does have a Python door lock, remote starter system. Wondering if it is killing the ECM randomly?

Really appreciate any help on this!!

 

crank=spins. i do believe i can decipher your post but that would be so much harder than trying to diagnose your truck

[http://www.73-87chevytrucks.com/techinfo/TroubleshootingTBISystems.pdf]Troubleshooting sensors and how to test

if its a tbi try this one
http://www.73-87chevytrucks.com/tech...TBISystems.pdf

Obd1 code retrieval and decoding

 

I apologize...……. spin = crank NO start
Thanks