It'll still spark. The timing light don't care if the plug is any good or not. It may or may not spark if the plug wire is questionable. So if your timing light is not flashing it is not the plugs fault.
Check your valve adjustments and put in a new set of points and plugs. Check your cap and rotor and replace if there are signs of uneven wear on the pickups. in other words perform a basic tune up.
