I own a shop and will try to help you. Turn on the ignition switch, test for power at the starter, and at the coil. There should be power at both places. When you jump across the big wire to the little wire you are bypassing the start side of the switch. If it starts there, then when you remove the jumper (screw driver) from it, it stalls. This means you are loosing the 12 volt supply to the run side of the switch. One wire is to activate the solonoid, and the other is to keep it running when the power falls off. Do you have these wires crossed? The one to the inside (closest to the motor) should have power "only" when you turn the key to the start mode. The other should have power on it all the time, when the switch is in the on position. If these are crossed it will act just as yours is doing. If you don't have power to the coil with the switch on, then there is a problem with a fuse somewhere between the switch and the coil, or a bad neutral safety switch, or a bad wire. The + cable comes to the starter, and another wire is hooked in the same place that supplies the ignition switch. Turn on the switch, and it supplies the coil. Turn it to start, and it supplies power to the wire closest to the engine on the solonoid to crank the engine. Find the one that doesn't have power when it should, and trace it back to the switch. You should find the problem by doing this. Glad to help you, good luck!!!