This thread may be helpful.
Post no.27 tells you how it works.
Therefore, any break in this part of the circuit will kill your sparks. Identify the cables and start checking for bad connections, broken cores to the wiring and chafed cables etc. (Bend the cables and if the core is broken you will find a tighter curve at the break.) If you are sure that all cables and connections are good, then you need to look for failed components. DO ensure you have fully eliminated the kill switch and ignition off circuits before you start giving yourself a big job.