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NEVER try to test the Coil High Voltage with a meter! The 20,000 volts or so will "fry" a voltmeter. Pull the coil wire from the distributor and replace it with one of the spark plug wires, connect a spare spark plug to the end and position it so the metal part of the plug is touching some metal part of the engine. Then, while someone tries the starter, watch for a spark at the "test" plug.
Reading 12v at the coil is good, but you need to measure it while cranking, as I said in my last post. Did you try the Temporary jumper from Battery to Coil#1 as I suggested? If not, why am I here?
Here is what SHOULD be happening:
1) Key ON 12v flows from Coil #15, through the Primary winding to #1, and from there to Ground (as controlled by the Ignition CU (ICU). This builds a strong magnetic field in the Primary coil winding.
2) The engine is cranked by the starter, and the Distributor tells the ICU when a sparks are needed (the Primary winding gets its +12v from a special starter circuit while cranking. Or at least it should.)
3) The ICU the creates the spark by OPENING the 12v Primary circuit (i.e. removing the ground at the coil #1).
4) This causes the strong Primary magnetic field (see #1) to collapse.
5) The collapsing Primary magnetic field induces a High Voltage in the Coil Secondary winding. This HV seeks a path to ground via the plug wires and spark plugs, and jumping the plug gap to create the spark that fires the fuel.
As I said, you may not have a good 12v at the Coil (step 1) while cranking. This is a known cause of problems, especially with a car that hasn't run in years. Which is why I'm asking you to test it and let me know what you find. If it's good, we can proceed to test the other steps.
P.S. Is the 3-wire Distributor Plug round or rectangular (Bosch) shaped?
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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