Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to spark electrodes
Remove electrode leads from spark generator

Measurement:

Inspect the electrodes / leads for signs of damage and measure the resistance across the electrode tip and end of the electrode lead for both electrodes.
Expected resistance continuity (zero resistance) on both electrodes.
Is resistance measured as expected?
Note.
1. Ensure a good connection is made to spark electrodes otherwise misdiagnosis will occur.
2. Electrodes shown removed for illustration only.