Normally the high voltage section of the coil is totally isolated from ground. The circuit is completed through the spark plugs when they are screwed into the cylinders. Voltage is supplied as needed. If one plug wire is grounded, the other should jump a 1/2" gap. If they show unequal voltages, the coil has become internally grounded and should be rewound or replaced. Since you have replaced the spark plug wires, no other explanation is logical. . . 😕
