Open flue lpg wocester boiler,in caravan ignition sparks ok gas supply to gas v/v ok .van recently moved no go

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Answers:
Pilot jet probably blocked. Need to fit a replacement as they are too small to repair.Could also be air in the pipework. Need to purge the pipe to the boiler. These are jobs for a LPG CORGI engineer as it is against the law to do ANY gas work yourself.