Hello Everyone,
My '69 Cougar (identical to '69 Stang for this purpose) has been having these weird spouts of terrible running, popping, stalling, and fluttering for about a minute, then they go away… Weirdest thing. So I hook up a timing light to see if my distributer was screwing with the timing (just installed new one), and I realized that the light wasn’t flashing regularly when the episodes occurred. Quickly, I ran and grabbed my volt meter and realized the voltage to the coil was fluctuating in-between 10v and normal voltage. When it normalized, so did the engine problems. I realized when I wiggled the wire, it would have another episode. Figuring a lose connection, I pulled the harness (which is is not to good condition), and replaced all of the wire up to the connector with new wire. Then I cleaned and reconnected, and tried to start again… A few minutes later, same episode. So I wired the coil directly to the battery and it STILL had the same problem! I’m completely lost. What could this possibly be?
For a conventional points/condensor ignition system, the negative side of the coil goes to the distributor but it connects to the points which in turn connects to ground. For a Duraspark system, the negative coil wire goes to the DynaModule, which then goes to the distributor and eventually goes to ground as well.
You should also put the timing light on each spark plug and see if the one of the plugs is behaving erratically. Remember as the coil transitions from primary winding to the secondary windings, the ground is now the firing spark plug.
BTW, unless your distributor is rated to run with 12V, you should either make sure to use the resistor wire or a ballast resistor or else you could damage the coil.
Hey guys, I fixed the problem! I replaced the cap and rotor, because they looked like they needed it, the negative battery lead because it looked like it needed it, tightened the ground to the block (very loose and very suspect…), and replaced the voltage regulator because it was sending to much power to the battery. Problem fixed! Don’t know what it was, but I’m driving to school and work now, and it’s driving better than ever!