1. The JumPack might not be fully charged. Press the button on the JumPack to test the battery condition. All four LEDs should illuminate.
2. There might be a bad connection with the battery cables. Try the following:
-Unplug the jumper cables from the JumPack.
-Wiggle the battery clamps to help make good contact.
-Plug the jumper cables back into the JumPack.
-Try starting the engine.
3. If the battery in your car is near 100 percent dead, or if the battery is defective, then it can suck too much power from the jump starter so that there is not enough power to start the engine. Do the dash lights come on? Does the radio work? If everything is dead then you may need something bigger than a portable jump starter.
4. If the engine cranks but refuses to start, then there might be a mechanical problem with your car that requires servicing.
5. There is a non-replaceable fuse in the jumper cables for your JumPack. If the fuse is blown then the JumPack will not work. The fuse can blow if the cables are accidentally shorted together, or if your car draws too much power from the JumPack. It is easy to check for a blown fuse using a voltmeter. Simply plug the jumper cables into the JumPack and check the voltage at the battery clamps. If you do not get any voltage then most likely the fuse is blown and the jumper cable assembly will need to be replaced.