Hello, I have an old worcester heatslave 9.24 boiler, this morning it fired up as usual but the gas ran out. I put some more on the meter but now the boiler won't light. I guess it has sucked all of the gas out of the pipe, I have just spent the last 20 minutes with my thumb on the pilot button with no success. Is there a quicker safe way to get the gas through so I can light it?