My 1967 Camaro has a starting problem. When I turn the key, the radio and acessories come on and it will usually fire right up, but on occasion, nothing happens. I turn it to start and there is no attempt to even turn over. Is it the switch? I bought it with a MDS ignition system in it already. Help! I'm going crazy!

 

It has sompthing to do with the starter circuit. Could be anything from the battery to the starter or cables running to the starter. Could be neumours other things. Does not have anything to do with MSD.

 

could be a couple of things
the switch like you said
the sol. on the starter, do you hear it clicking?
or the netural saftey switch

 

Ignition switch, starter selnoid, neutral safety switch, fusable link. etc.