Why does the engine shuts down 3 seconds after I start it? And it does every tme

What is your question?

My 1993 Toyota pick up turns over and starts right up, runs perfec for 3 seconds, then dies. However, just as it starts to die, if I turn the key to the start position, of course the starter grinds, but it seams to cause it to run again for another few seconds and dies again.

What makes this problem better or worse?

Nothing, it's constant

How long has your 1993 Toyota Pickup had this problem?

Just started after I replaced the power steering hose.