1990 plymouth laser starting problems

hi my name is Frank i just got a 1990 plymouth laser 2.0 turbo engine U with a DOHC 16 valve (91kmillage) and i cant start it it wont start with the key i have too push it for it to start i have replaced the ECU,sparkplugs, the timeing is on,the fuel is in order same with the spark im gettin air i dont know what wrong with the car i think it might be the throttle position sensor or the fuel regulator i just dont know what to do im hopeing some one can tell me what wroung.