Hi James.
Here's your first test sequence for the low tension (low voltage) side of hte ignition circuit.
Its important that you use a
test light to do the following tests. A voltmeter doesn't provide sufficient load. Halfords or similar should have a test light if you don't own one. It needs to use an incandesent lightbulb, not an LED as the ?LED also doesn't provide sufficient load.
1 - Turn the ignition switch off.
2 - disconnect BOTH low tension wires from the coil. Take a photo first so you know which one goes on which terminal (it does make a difference).
3 - Turn the ignition switch on - lights on the dash on, but not cranking over.
4 - Using a 12v test light check the voltage on each of the disconnected wires. Clip the test light lead to a GOOD earth point and probe the terminals. One should light up your test light. This is your ignition supply to the coil. If neither lights your test light, you have an ignition supply problem. Stop and fix it.
5 - Now have someone crank the engine over while you check the ignition supply wire. It should still have 12v on it when the engine is cranking. If it doesn't, you have a cranking ignition supply problem. Stop and fix it.
6 - Turn the ignition off.
7 - Now connect your test light between (so, clip on one of the wires, probe on the other) the ignition supply wire and the other wire you disconnected. This is the wire from the ignition amplifier and it switches the coil on and off by breaking and making the circuit to earth.
8 - Crank the engine over. Your test light should "pulse" on and off. It will be quite a rapid pulse and may show as being a wavering, dim glow. If it doesn't light OR it stays lit and doesn't waver, you have a problem that is PROBABLY in the ignition control circuit. Stop and fix it.
9 - Reconnect the ignition supply wire ONLY to the coil. Reclip your test light to an GOOD earth point.
10 - Turn the ignition on (not cranking) and use your test light to check the OTHER terminal on the coil (the one you haven't put a wire back on). The test light should light up. If it doesn't, you have a duff coil. Stop and fix it.
11 - Turn the ignition off.
12 - Reconnect the other wire to the coil.
You have now tested and confirmed the status of the entire low tension circuit and there is no OBVIOUS reason the engine should not start from an ignition pov. This disregards high tension problems which are possible - most likely in the distrbutor.