Start a car without a key?

Basically your finger print reader would be to turn the ignition on. Use a push button to start it

an older car may have a steering wheel interlock that needs a key so I hope you only need to make it start, not drive-able

You cannot rent a car at your age.

You cannot modify a rented xar.

It is already being done with implanted chips.

The big issue is getting the fingerprints read and accepted.

Then you need it to trigger a relay to turn on the ignition.

If the brake is pressed and the car is in park 10 seconds later trigger the starter. You stop the starter after 15 seconds or when the engine fires. You need a way of sensing engine start.

Modern push button start cars already have most of this.

As long as the keys are in rhe car they start.

You can't rent a car at your age and you certainly can't modify a rental car in any way, so forget that.

There are already a number of cars with remote and/or pushbutton start.

You would simply figure out how to wire a 12V fingerprint sensor into the system.

If you have a finger print scanner that'll run at 12 volt you can, where you put the key in the ignition on the back of that will be a black box with wires connecting to the key barrel, strip black and red wires connect your scanner then this can prepare the car for starting, but you will need an extra button wired to the starter motor wire, witch only need to be pressed untill started then released, this all depends on age and model of car but could be done, old cars are best for basic wiring and mad inventions, you can do it 👍

You will need the schematics of the car you're putzing with...but when you turn the key to on, you're energizing the system. When you turn it to "Start", you're making momentary contact and closing the circuit to the starter.

So whatever you devise, it should be making momentary contact with the starter motor circuit and powering that to spin. But you'll need an easy way to put the car to the "on" position first or while you're doing that.

You might want to look at the ignition schematics for any car that has a push button starter or works on a remote starter key fob.

your scanner basically needs to control a relay .. you could make it all electronic, but it would probably be easiest to have the relay 'unlock' a push-button starter switch ..

I also might rent a cheap car