HELP! HELP! HELP! my baby wouldnt start

[LovingMy240sx]

Hey fellas, i really need your help on this one. got a engine swap done 2 weeks ago for my 95 s14 base model but still couldnt take it out for a drive cuz it was missing a MASS AIR FLOW sensor.
ok, so now i finally got the sensor but i had no clue how to wire that shit. so i drove my 240 out to my local mechanic with only the intake and filter. on my way there, about like 13 blocks, i stopped at the red light and suddenly the engine just shut off. i tried starting it again but it wouldnt crank. i tried jumping it but it wrong start or crank. i check the battery, and there was nothing wrong ( the reading was normal). Im not sure if it is the starter problem or maybe the alternor or something else? plz help me out. I just got the engine and there is nothing wrong, no smoke nor burn smell. plzzzzzzzzzzzzz help , i want to get my baby back on the street again. thanks