Gq patrol coil voltage

[Fuddled]

Hi guys I'm having problems with my tb42 backfiring I fitted pertronix 2 and extended rotor button it's running a gt40r coil with ballast at back of ballast I was getting 13.8 and at front 12.8 and same on coil what voltage should it be could this be my problem thanks guys

[Yendor]

Yes, Those are around the voltages I would expect to see when using a voltmeter, with the engine running.

A voltmeter is to slow at reading the rapidly changing voltage at the coil, it will just display an above average reading.

To get an accurate reading you will need to use an oscilloscope.

The 13.8 volts to your ballast resistor is good.

I would be double checking the timing, spark plugs, leads and cap before replacing the coil.

Something else to try is, disconnect all the extra wires from coil such as tacho and radio suppressor.