Great weather over the weekend, time to take the Mustang out of hibernation. Charged the battery when I got home on Friday with plans to start-up on Saturday, adjust the timing (installed electronic ignition over the winter), and maybe wash the car. On Saturday, got the engine to crank but quite not enough gas to start so stop cranking, pump the accelerator a few more times, and ... nothing. No crank, no clicks, NOTHING. Scratch my head a bit and figure that as "nothing" was occurring and I had just charged the battery, maybe there's a problem the battery didn't hold the charge. Pull the battery & head to Advance to get the battery tested. Battery checks-out fine so I buy a replacement starter relay as that is the next component in-line. Get the new starter relay hooked-up and still nothing. Hmmm ... turn-on the headlights and they don't illuminate. My battery charger has a jump-start feature so hook that up (headlights are ON!) but when I attempt to start all I hear is clicking from the relay. What is going-on? Read through the troubleshooting portion of the shop manual and it is talking about jumper wires to determine "the bad component" but something doesn't seem right as the car ran after I installed the electronic ignition, only change since then is the new starter relay & I have triple-checked the connections ... I need to think about this for a bit. On Sunday I got an idea the headlights came on when the charger was hooked-up for the (attempted) jump-start not because of charger power but because of the connections made for the charger: charger-positive to battery-positive & charger-negative to an engine crossmember for a ground. Took some jumper cables and connected battery-negative to the crossmember ... car starts right up! Undo the jumper cable connection & same problem occurs so there's something on the "ground" side. Tracked the negative battery cable to the block and the connection to the block is kinda loose -- I even heard a small "zap!" when I moved the cable a bit. Tightened-down that bolt and voila! Problem solved. It looks like that one bolt was loose enough that the vibration of the starter jarred the connector away from the block so when I attempted to start the car, there still was no circuit being made through the starter.