If you can get to the starter, under frame ,locate ignition wire that "energizes" the solenoid and remove it.
This better be done AFTER Neg batt term disconnected for safety , safe-off by taping loose wire , re-connect battery and turn key to start . You have eliminated solenoid Short ckt. Continue by removing successive relays upstream as you go , Schematic a must.
TIP - buy those Ckt-Braker fuses that reset ,if size available, $4 ea ? Saves Blowing all those "test fuses"
Use your ears to listen for any sparking , your nose - sniff out smoke/hot wires as precaution as you go,anytime connecting a "jumper" from B+( Battery Voltage) - have a FUSE IN SERIES to your test destination.Lastly , never use larger fuses into the fusebox - you WILL smell smoke/see fire !