I turn my van on and it turns off in a few seconds?

Hello,

This issue could be due to fuel starvation. If there is inadequate fuel pressure to the injectors it can shut the engine off.
If there is a clog in the fuel line or a faulty fuel pressure regulator can cause the fuel not to reach the injectors properly. It can also be a weak fuel pump.

Check the fuel pressure using a fuel pressure test gauge. You can get those tester from your local auto parts store to use.
This vehicle should have 49 PSI of fuel pressure with the key on and engine off.

Here is a helpful guide:

https://youtu.be/aITQclp7zIE

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

On this vehicle the fuel pressure regulator is part of the fuel sending unit and the fule filter is located on the top of the fuel tank.

Please let me know of any questions.
Thank you.