It only runs when the starter is engage because your ignition is picking up power from the hot start wire connected to the solenoid on your starter. What this does is give your ignition a full 12 volts when starting only by bypassing your ballast resistor. So the thing to do is turn the ignition switch to the run position then get a test light and see if you have power to the ballast resistor. Then check to see if you have power coming out of the ballast resistor. You should only have 9 volts coming out but you will need a volt meter to check this. If there is no voltage coming out of the ballast then the ballast is bad. A simple test would be to put a jumper wire from one side of the ballast to the other then start the engine, if it runs then you have found your problem. Also check for loose or broken wires....Big Tim