Disconnect cables from fuel pump and from glow-spark plug.
Install a 4 mm diameter screw in the angled connector of the ignition cable.
Turn heater on. When screw is held at a distance of .28” (7 mm) from suitable ground, a continuous spark must jump across the gap. (Hold ignition cable with insulated pliers.)
If there is no spark, measure the voltage at terminal 15 of the ignition coil with a voltmeter. The voltage must be at least 10 Volts. If the measured voltage is lower, check whether there is voltage when the contact breaker is open and no voltage when it is closed at terminal 1 of the ignition coil with a voltmeter or a test lamp. If the voltmeter needle does not move, even when the contact breaker is open (contact breaker is not shorted), the ignition coil has open circuit and a new coil must be installed.