Cranks good and engine start for 2sec on first start then only cranks

[broken]

Good battery
New ignition switch

4,4 v8

So today when i try to start the car it started on first attempt and dies after 2sec. No missfireing seems to run smooth and then just dies. Second attempt same. Third attemt i gave some gas and runed up to 3000rpm then dies.

Tried couple of hour later
Starts and dies after 2 sec. Second time only cranking.

So what to start with?

Try some start gas and see if its fuel related?
Check sparkplugs for spark?

After some reading here im guesing:
Fuelpumprelay?
Relay for DME?
Crank shaft sensor, or is this only in use after start up?

OR

I had the cheak engine light on the other day and had the codes cheaked out:
it was the preheating for the o2 sensor(lambdasond)
The indy errased it and the light whent away.


Please any ideas