Good tips from all. This has been a good read. Electrical is scary? No need to be. Frame and sheet metal is ground. Wire is how things get connected. So why 2 wires on the + on the coil? one is "run" from the key switch. That can be from a 6 volt source, a resistor wire, or a ballast resistor. The resistor wire cuts 12 volts down to 6 volts. The ballast resistor does the same thing. The ballast resistor can hide. It can be on the firewall, or inside the coil. Inside the coil is just a simple way to get a so called 12 volt coil. So why all this fuss about 6 or 12 volts at the coil? Simple actually. The points are a switch. That switch was designed to work with about 4 amps of power. The coil was made to work with those 4 amps. and...the condenser was too. When cars and trucks changed to 12 volts. The engineers could see no reason to change the coil, points, and condenser. Tha accountants would not pay for it any way. So an inexpensive resistor was the fix. Wire, ballast, or inside the coil. Same cheap and effective result. 4 amps at the points. The second wire on the +? That is from the starter. Foot or solenoid. It is to help with cold starts. Temp push of extra current to make a big spark. Off when the starter is off. simple and effective. So you have two simple tests. Test 1: key on in the run position. Volts at the + . 12 volts? you have a 12 volt coil(the one with a resistor inside) . 6 Volts? You have a ballast resistor or a wire resistor. Just a note: the points need to be closed. If they are open the circuit you are testing will be open. Volts reading will be funky. As in not useful. A ground strap is helpful to get past the rubber in the motor mounts remember ground is...the frame and sheet metal. Test 2: Volt meter at the + and turn on the starter. 12 volts? All is good. Let the key spring back, and 6 volts? If you have a resistance wire or a ballast resistor, all is good. 12 volts? If you have a "12" volt coil. All is good. Did you check to see if you have a ground strap? Most ground straps go from the motor/bellhousing to the frame Some(not many but some) just jump over a motor mount to avoid that sneaky bit of rubber. So what can go wrong? Runs in start(starter on) and quits when in run. Bad resistor wire(covered in previous posts). Bad ballast resistor(also covered in previous posts). Bad coil? Not this time. The coil works with the starter. Bad ignition switch? Not this time. Again covered in previous posts. Bad ground strap? Maybe. bad connection on the "run" wire? maybe. That is a start. look at the easy stuff first. Cheap is good. Let us know what you find.
Steve
