This was posted in ef forum, thought I would get better response here.

My car acts VERY weird, sometimes it starts right up, other times it does not. I replaced the starter with a junkyard one, and the same thing happens.

Ok, main wire coming from battery gets full 12 volts, when cranked it still gets full voltage.
So heres the breakdown,
1. Signal wire(from ignition) cranked unconnected 11.45 volt
2. Signal wire connected/cranked 5.4 volts
3. Main wire(from battery) 12 volts consistently.
If I jump a wire from positive battery terminal to the small signal wire on starter it starts everytime.

 

Anyone?

 

check the continuity in your starting system. get a electrical schematic to trace where the wire is coming from, etc. Sounds like you might have a loose connection somewhere in the starting system or a damaged/ frayed wire causing a lost of voltage from the signal wire starting to the battery itself.