crank but no start

i have been able to rule out fuel pump plenty of gas coming through the fuel line when i try to start it.i have also been able to rule out my PGM relay because i replaced with another relay from another Acura that was running just fine.the only thing left is spark.i cannot see spark after a few tests.what could cause this?
I don't know what else i'm missing to test.
could camshaft sensor cause this?
please help.