hi i am looking for advice my friend has changed my cars engine fiat 500 1.2 2013 to a punto 1.2 2015 he was told they are same engines he used the old engine loom wirring when he tried to start the engine the ignition fuse blowed what might be wrong

Wrong connection somewhere..

Check earth cables.. then the starter motor

How many original parts were swapped?

only the alternator and starter and ecu was used from old engine

thanks