How can you start a vehicle without a working starter relay?

You may be able to jump the relay, also called a solenoid, with a jumper wire and make it energize, by going from the battery cable on the solenoid to the small terminal on the solenoid with S on it. If that doesnt work, you might be able to bypass the solenoid all together with a heavy duty jumper cable. Both of these could very well get you shocked or burned, so you must have an idea of what you are doing