When I let go of the ignition switch it turns off?

Hello,

So, when an engine just cranks and cranks but does not start, it can be due to either not getting fuel or spark.

Let's take a step-by-step approach to this.

Check to see if the fuel pump is operational. Can you hear it come on when the key gets turn to the on position?
An inoperative fuel pump can be due to burnt relay or a bad pump.
First check the relay. The fuel pump relay is located under the dash on the left-hand side (see picture below).
Check for any corrosion on burnt pin(s).
You can also test the relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

If the relay is good then check the wiring for the fuel pump, check the connector to see if there is power
If there is power but the pump is not coming on, then it is likely a bad fuel pump.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

If the vehicle is getting fuel, but still no start, check for spark. You can simply take out on of the plugs and crank the engine to see if it is producing spark. No spark can cause by faulty ignition coil, distributor cap/rotor or a bad distributor.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

I have attached diagrams including fuel pump test procedure as well as distributor cap and rotor and ignition coil instructions.

Please let me know of any questions.
Thank you.