Distributor coils/standard block coils can be checked by resistance measurement.
The resistance of the primary coil can be measured between connector "1" (Trig) and "15" (12V). Typical values are, depended on application (with/without ballast resistor), from 0,6 to 4 Ohm.
The resistance of the secondary (high voltage) coil can be measured between connector "4" and "1" (Trig). Typical values are, depended on application, from 3-11 kOhm.
Note: The resistance measuring method is a rough way to determine a general failure of a coil. Small variations (short circuit of some windings only) in the resistance are hard to detect with this method!
Due to the integrated ignition module, a direct access to the primary coil is not possible. Resistance measuring is therefore not possible.
In addition to periodic replacement of spark plugs, the distributor cap and rotor arm are components which undergo mechanical wear. Therefore they should be checked and replaced regularly.