Remove the cables from the battery and clean both ends of the terminals on both positive and negative, and then see if it will start with your battery. Might be both bad contacts and a weak battery. If the battery has a full charge and you still are having difficulty, then the cables have high resistance in them as a result of corrosion that has traveled down the copper wires under the insulation causing high resistance to current flow. New cables are not that expensive. Also, make a mark where the positive side of the battery is placed, and also make sure to mark which cable is the positive cable so there are no mix-ups like the last person that had a battery problem posted on the forums. In his case, someone installed a red cable for the ground, which should be a black cable. The last thing is that your jumper cables might not be of sufficient wire size to carry enough current to the vehicle being jumped. Good-quality battery cables are not inexpensive. My jumper cables are made from welding cable grade wire. 30' long and will carry enough current to start anything that you hook it up to unless the battery in the vehicle you are connecting to isn't large enough. You can't start a tractor that needs a big battery off a small vehicle battery. It is like fighting a house fire with a garden hose.