I have an automatic 240 and the engine died so we changed it with another engine that came from a 5 speed 240...Now the car starts but after 30 secs it turns off by it self! What's wrong with it??

If it cuts out like your losing fuel. Then it’s probably your fuel pump or the power supply to the pump.

There is a fuel switch on the ignition that turns the fuel pump on before you crank the engine and keeps it on for a few seconds. Usually the engine starts and the fuel pump gets power from a separate circuit.

Or the fuel pump could be worn out and build up enough pressure before the engine starts to run the engine for a sec and can’t keep up with the engine’s demand while running so it dies.

But hey just a thought.