Swinney, good questions, you ask
1) "This might be a silly question but , if I take my test light and put it in the coil where the wire goes should it light up ?
Problem with that test is if you have a typical what I suspect low voltage 6/12 test light, the coils top HV output tower is several thousand volts (when good points conduct coil current then open) and may well NOT yield any visible short term HV light output like 12 steady DC volts would produce and may damage the test light !!!!!!!!!!!
2) But when I put the wire in and hold it up to the block it has spark.
That's what I would expect if all is working, you're looking for a good visible bright blue spark to frame at approx. 3/16 inch NOT any faint thin wimpy hard to see yellow spark
If you have a good bright blue spark out the coils top HV tower (via a wire to frame ground gap) when the coil fires but NOT any spark out of any of the plug wires to ground or across a good correct connected plug gap, THE PROBLEM MUST BE THE COIL WIRE,,,,,,,,, OR THE DIST CAP,,,,,,OR ROTOR,,,,,,,,,,OR THE WRONG CAP OR WRONG TIMING whereby the rotor tip isnt lined up with an internal cap pickup when the points break open.
I have seen INCORRECT DISTRIBUTOR CAPS cause that or they weren't installed correct either of which isn't allowing the rotor tip to be in line with a caps internal pickup when the points open and the coil fires
With the cap off and ign off slowly turn the engine over until the points just break open ands stop,,,,,,,look at the cap and where it would be if installed and see if the rotor tip is lined up with where one of the caps pickups are located,,,,,,,,when the points break open the rotor tip should be close to one of the caps internal pickups...IF ITS THE RIGHT CAP AND INSTALLED CORRECTLY
If you have no fire at all you can work through my Ignition Troubleshooting Procedure linked below BUT if you get a good bright spark out the coils top HV tower the points etc is working but no fire out any of the caps terminals I suspect the cap or rotor or wires or wrong cap or a distributor or timing problem.........
NOTE ALSO when you say it runs rough ARE THE PLUGS AND WIRES IN THE CORRECT FIRING ORDER SEQUENCE ????????? If not she may run bad or not at all depending on how many if any wires are correct BUT THAT WOULDNT CAUSE NO FIRE OUT THE COIL AT ALL IF ALL ELSE WAS OKAY
I take it the distributor is installed correctly ??????????
For this discussion I'm assuming you have the correct voltage coil (for example not a 12 volt coil on a 6 volt tractor etc) and the points and condensor are all okay ARE THEY ???????????? I AM ASSUMING you get a good spark out the coils top HV tower but no fire to any of the plug wires or plugs IF THATS INCORRECT LET ME KNOW AND I WILL PROVIDE A DIFFERENT RESPONSE !!!
Wrong cap or not installed right,,,,,,,,,,rotor or cap problem,,,,,,,,,,,incorrect plug wire on cap firing order,,,,,,,,,,timing or distributor problem,,,,,,,,,, ???????????????
Let me know, post back your findings and any questions
John T Retired Electrical Engineer
John Ts Ignition Troubleshooting Procedure