Car not starting even with jumper cables

If the terminal connections are corroded or loose, electrical flow to the rest of the car will be restricted, so your car won't start even with a jump. Removing the cable ends and cleaning the corrosion with a wire brush (and retightening the bolts) should restore full electrical power to your car.

No, a car battery is never “too dead” to jump-start. If the jump-start doesn't work, you may have a faulty alternator or a dead battery that necessitates a replacement.

What if your car won't jump-start? First, try running the other engine for five more minutes before trying again to start yours. If your car still doesn't start, you may need a new battery — or it could be a sign of a more serious problem.

If jump starting gets your engine started and running, but the car will not start again once you turn it off, the battery is probably the problem. In this case, the alternator is doing its job of keeping the battery going once it has been jumped, but the battery can't hold a charge when the alternator is shut off.