help car wont start

i have a 98 sl2 with a 02 s series engine and have had no problems with in the two years since the swap till recently, anyways i go out this morning to go to work and it wont start. i tested the battery and its fine, its turning over, have no clue what it could be, ive also had problem with it dying as im goin down the road, when this happens it acts as if it had no power at all everything goes black, can someone help me
:banghead:

The first thing i would check is to see if the fuel pump is working.Turn the key to the run position and have somone back at the fuel tank listening.You should hear the pump run for a few seconds.

check for spark, fuel pump.