The one condenser for 2,3 has started to explode. And I have no visible spark on the breaker points...
Do you mean to say it is swelling with use? If so, that is likely a faulty component.
No spark at points can mean the coil isn't building/ storing enough energy. Perhaps due to the condenser increasing in internal resistance.
If you have an ohmmeter, you can place a probe on the body and one on the lead (component out of circuit). The reading should initially surge (capacitor charging) then subside to zero as it reaches full storage potential. Each time you reverse the test leads, the surge/ behavior should repeat. This will allow you to observe the capacitor action, but not give you a capacitance value. For that you need a capacitance meter, which is not a common household device.
Analog meters inject higher voltage into the test device, and the needle's inertia helps to visualize. But, digital meters can be used also if the specific design allows. Sometimes you need to select the diode test function, as that uses higher voltage for the test. It shows as a reading jump with a taper down to zero. The higher the capacitance the slower the reading change.
However, a bulging component is not usually a good sign. Did you have a functional reason to replace the old ones? Do symptoms change if you put the old ones back in?
Cheers,
