This is basic electrical troubleshooting or elimination process. Depending on how quickly the fuse is blowing will give me the hint of how bad it is. Also is the correct size fuse in there? I will have to fire up my old computer to double check but I think it was a 15 amp. The Ign. circuit is purple and several things are energized through this circuit. If the fuse is blowing quickly it will be easier to troubleshoot. Either way I would start at the ign. switch, pull the purple off, turn the ign. on & nothing should happen, if the fuse blows you have bigger problems.