ls1cutlass

I have a quick question my swap is about done i can get the motor to fire up but it only runs for a couple seconds and then dies is vats shuting it down. I Thought vats only shut down fuel does it cut out spark i havent had vats removoed yet. didnt no if low oil level sensor or somthing else was shuting it down. I have seperate setup controling fuel pressure so i no i have that think iam loseing spark