Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove ignition electrode from its housing

Measurement:

Test 1:
Check the ignition electrode gap at the tips of the electrode.
Gap between the electrode tips should be 3mm +2mm/-0mm.
Test 2:
Check the gap between burner and electrode. This necessitates
burner removal, then by turning the burner and using it as a
straight edge a measurement can be made. The gap between
the straight edge and the electrode should be 11mm +0mm/- 4mm.
Test 3:
Inspect the electrode visually, it should be clean and free from corrosion.
Note:
Before reassembly check the integrity of all disturbed gaskets and seals and replace as necessary.