Even though your battery tests at 13v, it doesn't mean it's strong. Try putting your light on hi beam and leave them on to see how soon they dim out. Unless you have led's, the lights should stay on 10 minutes or so. If not, then your battery is too weak to turn over the engine. I've found with a bad battery, with good voltage with a charger boost, my bonnie would not start, new battery, no problem, battery problems can be confusing.
Hoopla
