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Rolfe;
What if points happen to be closed when you make measurement you describe in (1)? ...and (2), is not clear to me at all!
Don't take this wrong, I know your trying to help here, but when giving advice, it is important to be clear, concise and correct! (That's why my posts are often long...here comes another one...hopefully, this will leave no doubt!)
usul;
Ignition consists basically of two functions: Coil generates high voltage spark, and distributor cap and rotor route this spark to the appropriate spark plug. You should divide and conquer the two functions! To troubleshoot, FIRST, you must determine if coil is generating a spark when the points open, ONLY THEN can you check to see if it is getting to the plugs!
To answer your original question. The simplest check of the spark coil while in the car, is done by disconnecting the "points" wire at the dist. which connects the points terminal, to the (-) terminal on spark coil, routing the high voltage output wire from coil to chassis (and leaving a spark-gap about the size of a spark plug gap, which can be watched), turning ignition ON, and alternately connecting and disconnecting the "points" wire to the chassis. Every time the connection in BROKEN, a spark should occur. If a spark occurs, the coil may be considered OK.
Move on to check if the points of the dist. are doing the same thing to tigger the spark coil (by alternately closing and opening)...while "points" wire is still disconnected from dist (IGN OFF), use an ohmmeter to verify that the points of the distibutor are alternately supplying a connection to chassis, then opening. (During normal operation the closed points allow the spark coil primary to build current, and opening the poits triggers the spark from the spark coil secondary.)
As already mentioned, problems can occur if points terminal on dist. or points themselves are shorted to dist housing due to incorrect installation but also breakdown of paper insulator, or fibre washers, or failure of capacitor (rare).
FYI. If you car is an early 1800 with an armoured cable to the IGN switch (Ign coil has a SINGLE terminal visible next to the high voltage output wire), a late model will have TWO terminals visible. Operation, and test are still absolutely the SAME, it's just that the IGN power is supplied by way of the armoured cable in the early style.
Let us know how you make out.
Cheers
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