I'm a little confused. Do you have a battery in the vehicle? If so, it should be a 6 volt positive ground. Are you using jumper cables from another battery and possibly crossing polarity with the battery thats in the vehicle? If you have no battery in the vehicle, its pretty hard to get enough amperage through most jumper cables to crank a 6 volt. If you have light jumper cables, its quite likely that it will only sputter at the clamps. I use 4/0 cable with 500 amp welding clamps for a jumper cable on 6 volt.