As I sit here typing this my hope is that you have already fired the old thing up...(-:

As it seems you have decided sparks were the issue I thought it perhaps worthwhile to try to explain my basic understanding of the general layout of the system you may be dealing with given I have no other demands on my time right now.. (-:

I suspect wiring diagrams may confuse many who have a degree of electrical understanding at times, perhaps a description of the operation might be of assistance..? In that regard I thought it might be helpful to provide a rough outline of that which you may be dealing with..?

I defer in all matters electrical to RichardV6`s advice as being entirely correct.

As best I can remember, the design of incorporating a resistor in an ign coil circuit is all about providing the maximum spark possible from whatever voltage might be available from the battery when you engage the starter motor via the ign key..

In a situation of semi regular usage....... In the UK`s oft times cold and damp weather, starting 70`s engines even in the 70`s could present issues, and more so if the battery was not up to ideal voltage levels. If you consider that the battery may have dropped voltage by some degree since the last time the engine ran, even if it was as recent as the previous evening.

The heaviest electrical load on a battery is the starter motor, and when you turn the key chances are that the voltage in the battery will drop, the older the battery and less charge/voltage it has as it`s stored energy supply, and the more the voltage will drop when you turn the key to the START position.

The idea behind the resistor in the coil circuit is based upon the choice of coil it`s self and in a resistor circuit the coil is not designed to operate at "normal" battery voltage in the Morgan`s electrical system, but is designed to operate at a lower voltage, perhaps somewhere in the region of 6 to 9 volts. The idea being that when you turn the ign key to the START position, whatever voltage might be available from the battery is provided direct to the ign coil to improve the chance of creating a strong spark, hopefully resulting in the engine starting after variable periods of inactivity.. On the other hand the available voltage could be 12 volts or more if you only shut the engine down a few minutes before, The dual circuit, feeding the coil being either direct or via the resistor is designed to cope with the expected voltage variables in the Morgan`s normal operation, even with an old and failing battery.

The battery when trying to turn the engine using the starter motor, supply voltage to the coil to create a spark, and perhaps run an electric fuel pump, is working hard to take on all those tasks, and as a result it`s voltage might be expected to drop to some degree... ? That being the case a twelve volt coil would be looking for as close to twelve volts to provide the best spark available, at a time when perhaps less than twelve volts might be available, and if so it seems there is much less chance of producing a good strong spark, and the engine firing up..?

With an ignition coil designed to operate at less than 12 volts, chances are that it will produce a strong spark even when the battery voltage has been forced to drop by some degree while the starter is turning the engine over...?

In an ignition circuit incorporating a ballast resistor, the ign key may control two wires leading to the coil. With the key held against the spring in the START position, whatever voltage is available is supplied to the coil via the wire connected to the START terminal of the ignition switch, and when the key is released to return to the IGN ON position, the coil is fed through ON/RUN terminal of the switch to the wire which has a resistor in it`s circuit, and which drops the voltage available to the coil to a level which more suits it`s designed running operating voltage. The thus the coil having supplied a strong spark with whatever voltage was initially available during the engine START process, ideally the coil is then supplied with a voltage at which it was designed to RUN at normally.

Quite how the above is achieved can be through a couple of different designs, in some Ford circuits the RUN wire from the ign key might be grey in colour and which due to it`s dimensions has a resistance along it`s full length which drops the voltage available at the coil.

Another type has a separate resistor mounted on or near the coil which is easier identified as a separate unit.

When the resistor or the wiring to it fails, it is possible for the engine to fire up with the ign key held in the START position, but to stop firing when the key is allowed to return to the normal ON/run position.

Another circuit failure possibility is when churning the engine on the starter it fails to fire up, but the instant you let the key go it fires up, which indicates that START wiring or connection have issues.

Either of the above could be at the location of the key switch, but more usually in the engine bay.

Connections at the coil are polarity sensitive so best to take time to identify the type of coil and it`s operational requirements. In the seventies the usual design was that both the START and RUN wires are live/hot and are supplied to the coil from the ign key. The earth/negative/ground wire is connected to the distributor, for it to control the switching of the spark timing.

Dependant on manufacture, coils can come with their terminals marked in a variety of different ways best to identify what type of coil you have, and whether it is designed to be operated by a distributor with points or by electronic means. Coils usually have markings at the connections and manufacturer I.D. elsewhere.

Chances are that your original coil if of the type originally supplied in your Morgan may well be the last part of the circuit expected to fail...

However so many Morgans are modified by their owners it seems best to identify whether the kit in your Morgan is still original or has been modified to some other specification..?

Hopefully I have provided a reasonable outline of the ign circuit design and not muddied the water. Ever happy to be corrected if/when I make mistakes...

Good luck.