have a 68 289ci 2bbl - turn the ignition key, and nothing. I jiggled it around - rattled the harness and it started. I got it home. 2 days later, I pull it out of the garage to check it out and nothing. Battery has 12.8 V showing on tester, solonoid and relay seem good but how do I test them. OR fearing the worse is my wiring so shot its time to replace the 40 yr old harness?