Breckwell G29v.....kick it on

I have a Breckwell G29V. It started not comming on sometimes and if you banged on the side it would come on....it slowly got worse so that we would have to kick it hard. but once it heated once and would go off it would never come on again without kicking it....anyone clue me in on what the problem might be?

Thanks,..ill try it

perhaps a bad valve--Bob's idea would be a lot easier to fix though, so i hope its justwiring...
i've seen robertshaw valves that needed a tap to get the pilot magnets to engage when the pilot was blown out