The cooker clicks but won't light: the dry cap, the spark gap, the pin in each port

A cooker that clicks and clicks and never catches is either a spark that can't reach, a flame path that's plugged, or a gas that's not arriving - three faults, a different fix each, and the match test tells you which in one second flat. All of it stays safely in homeowner territory until one particular smell ends it, and the end line is printed below the ladder.

Three minutes, in order

1. Gas smell at the bench, even faintly, before or during these checks: stop - cylinder valve off, open everything, no switch, no flame, find the leak's join first. This is the soap-foam chapter's job, and it comes first because everything else can wait for an hour.
2. The cap is the number one fault. After cleaning, the burner head's black cap sits a hair off its seat or still damp, and the spark jumps to the wrong gap - dry it, seat it flat, give it a quarter-turn to bed it; every burner has its own cap and a swap between neighbours mis-sizes the hole. Test with the match: lights fine with a match now and again on the knob's click = ignition problem, not gas.
3. Ports. Boiled-over starch plugs the small flame holes around the cap - with the cylinder off, a needle or pin through each port, a dry brush around the ring, cap back. A burner with a clear port ring but still only half-lighting has a clogged jet at the elbow behind the cap - the burner's one job for the technician with the right needle set.
4. The spark itself. Look into the burner while someone presses the igniter: no visible blue-white flick across the 3-4 mm gap is a dead piezo (the clicker in the knob - replaceable on the bench, market cheap) or a corroded lead from it; a spark that's there but the flame never catches - even with a clean cap and clear ports - points back to gas, and with gas the sequence is cylinder valve fully on, the regulator's safety trip reset (off at the appliance, wait half a minute, on slowly - a tripped flow valve is the "burner works on one, not the other" story), then the oven/broiler's separate jet if the hobs lit.

The honest line, and the prevention

Everything above is cap, port, spark, valve - no jet sizes, no gas-line soldering, no regulator internals, none of which this desk has ever endorsed at home with the cylinder in the room. And the prevention paragraph that stops the repeat: boil-pot means the pot's below the flame's top line; the tray under the caps gets wiped while the burner is cool and off, never spray-in the igniter's face (the cleaning fluid in a spark gap is tomorrow's "it won't light"); and the cap-and-ports half hour after a boil-over, dry in the sun, is the difference between a Tuesday evening and a service call. The one symptom not listed on purpose: a flame that lights and dies when the knob is released - that's the thermocouple, and that's the technician's twenty-minute fix, and it is unambiguous enough to book it on the phone the same day.