2002 lincoln ls V6 3.0

I have recently swapped the engine in the Lincoln (with same) and got it to fire up about 4-5 times. I couldn’t let the car run too long due to a cooling fan degas issue and not wanting to fry the impeller of the cooling fan. After fixing the degas problem I went to jump the car again and it would crank but not start. Lights good and bright, plenary of power to crank over. I checked the fuel pressure via pressing the nipple on the fuel line rail with no pressure being released.
Question: since car was starting and running (for about 30 secs to a min ea time) could this be fuel related and the engine just used remaining fuel in the line before not starting and no pressure in the rail line? Checked fuse 17 in trunk (fuel pump relay fuse)