I have a Vulcan floor standing gas boiler, some 30 years old. Recently I have had problem with the pilot light going out, maybe once a week. It seems worse when we have windy weather, but when I watch the main burner igniting/extinguishing (using the thermostat knob), the pilot light seems to 'stagger', as if the gas pressure to it is being affected by demand from the burner.
The gas valve is Honeywell, and I have adjusted the pilot light to give a good strong blue flame. The main burner is also adjustable, but I do not know the correct adjustment - the burner flame seems OK for the first 5 to 10 seconds, but then builds up in intensity and appears too fierce.
Any advice will be gratefully received. Thanks.

I think you have your answer " It seems worse when we have windy weather"

This is caused by a downdraft (wind) that blows out the boiler pilot light

Does it seem like there is a draft when you try to adjust the flame

Extending the chimney can help -- hope this helps you

Thanks for your reply, biggsie. However, I failed to mention that the boiler has a balanced flue, direct to the external wall, and about 15 feet above ground. This whole installation has worked OK for some 30 years - only recently has the problem occurred. I checked the flue yesterday, and only fault I could see was poor mortar seal between the metal flange of the flue and the wall, which I rectified. BUT, when I removed the blanking plate on the boiler front to inspect the flue from inside the house, I was surprised at the strength of the incoming draught of air, as the flue appears to be designed to prevent that.

I am having the same problem with an old Vulcan Continental boiler. The downdraft has got so strong that I can't even light the pilot light. How can I fix this?

The main gas valve has to be adjusted to the rate plate on the unit. There will be a firing rate /water collum figure that it has to be set to and it will read in inches of water.You need special tools to do this and I highly recommend a professional make the adjustment. You can tell nothing by just eye balling the flame.

One more item. On those boilers sometimes a draft diverter type piece of metal will rust away causing a down draft situation.

What I think is deflect draft at boiler or deflect it at the vent

So wind goes past it or is deflected over the top of it

Maybe it just needs a different cap -- different shape

We had same prob, just had to keep relighting boiler I'm afraid.
Does any body know where I can get a thermostat from for the same boiler Ta.

I balanced flue is call that because the incoming air and outgoing products are in the same air pressure zone so the wind pressure is balanced, the problem will be a damaged rope seal causing the boiler to become unbalanced. A gas safe registered engineer will easily solve this problem for you