91 chevy lumina just wont start???

i'm trying to fix my mother-in-law 1991 chevey lumina i've had the coils checked,repalced the control mod and even bougth a scaner and it comes up a 12 (witch means thats it checking it self). i put a curent tester in the spark plug wire and still comes up no current i dont know what to do now! can you help?