Won't crank

WHAT does this mean?

Can you twist the key (or have someone do so) and hear the starter relay?

Maybe the relay is pulling in and the contacts are bad.............

Didn't you say you can jump the relay and it will crank?

Need answers to above ^^^

I'm thinking it's likely there is corrosion on the relay contacts. Jumped it with 12v and it worked--it's working sometimes, but not always with everything else 100%...meaning the yellow wire has juice. Possible corrosion internal and/or external causing problem. Could replace relay, or clean up one you got. Just my 2cents.