I have a 1986 k5 blazer with the 305. It was starting and driving no problem a week ago but then out of no where it wouldn’t start. I put a different battery in it and I also put in a new starter. Still nothing. I then went and replaced the ignition switch and unplugged the netrual safety switch. The voltage meter comes on and when I try to start in the voltage drops. Even when I have jumper cables connected. What am I missing?

 

do you have power at the signal wire at starter while trying to crank? Just to verify you are getting your command at the starter itself.

 

Cant guess. Must start at battery and trace voltage it till it disappears. Probably a bad connection in a fusible link or firewall connector but dont disturb them before doing the tests!

Put a volt meter across the battery then move the + probe thry the circuit till the voltage disappears with a load.