Chonic Alternator Failure
So it's more a technique thing that an outright parts problem. Granted it's partly a parts problem too. I always insist on letting the running car sit there connected to the dead car for at least several minutes while on a high idle if not off idle before even trying to start the dead car. By first trying to charge the dead battery I've successfully jump-started with a pair of 10ga. wires. The running alt keeps the voltage up while the cranking current comes from the surface charge on the 'dead' battery.