ok heres what i got ...99 camaro wont start hhhad problem 3 months ago ...changed fuel pump , regulator , all filters , plugs . wires, by pass security system and after all that a new ecm before finally got it going again ....now haveing same problem again replaced fuel pump and regulator again all seem to be good ....ecm is good ...no security light ...changed fuel filter ....wont crank over well backfire and shhots white smoke out tail pipe and air intake ...tried to shoot starting fluid in intake nothing ....it will crank and crank till battery goes dead but wont start ....getting plenty of fuel preasure at rail ....dont get it ...help!!!!!

 

Have you check to see if the plugs are firing?