This is just weird. I just put a used 4.3 motor in a 96 S-10 Blazer and it wouldn't crank. Not a click, groan or anything. I thought I might of had something shorted out so I started pulling fuses. When I pull the O2 fuse, it'll crank but not start and the headlights stay on. If I ground one side of the 02 fuse the lights go out. With the O2 fuse removed, KOEO, I'm showing voltage on both sides of that fuse. 12 volts on one side and about 6 volts on the other and 12 volts at the ground pin at the starter relay. If I ground the circuit it'll crank but the fuse blows instantly. I'm guessing I have a bad ground but so far everything checks out solid. What a puzzle, and I can't find a connection between the headlights and the starting system either. Any suggestions?

 

02 Fuse?? O2 Sensor fuse?? Or fuse #2??

Electrical gremlins are not always fun but, it sounds like you might have something hooked up wrong. Hence the fuse blowing as soon as you ground the wire....so are you grounding out the fuse or the ground for the starter relay and it is blowing the fuse?

Here is a link for some wiring diagrams....you have to have a google log in or you cannot access them. Hope this helps.

 

I got it! It wasn't what was plugged in wrong, it's what I left out. A pair of ground wires had gotten pinched between the tranny and the block. I cleaned that mess up and it fired right up. Apparently it was finding it's own ground path and in the process turned a few more of my hairs grey. Thanks for the help!

 

Just to ****le, you had a wire or two pinched and shorted TO ground. If they WERE 'ground' wires you would never have known it.

However, your point is made

{silly word-nanny! n*i*g*g*l*e is blocked.}