All coils get constant power but the current only flows thru it milliseconds before the spark is requested. The ecu triggers the ptu to ground the primary windings in coil pack to “charge” and then release the charge resulting in spark. too much resistance n the signal will be to weak to ground the primary windings resulting in no spark but still show 12v at the secondary windings. I’m pretty sure it’s a fuel issue tho injectors should never stop briefly