[JSeery]

It needs to be somewhere around 1.5 ohms, but your not going to know anything until you check the coil to see what it is. It's volts / ohms = amps. You need to limit the current (amperage) across the point to somewhere in the 4 - 5 amp range. 6.8 / 1.5 = 4.5 amps, 7.2 / 1.5 = 4.8 amps. A higher resistance in the coil could be limiting the current/voltage.