Okay so the igniter sparks and this light but very faint flame that goes out means the electronic gas safety valve is bad, this is a common issue with these unfortunately. the gas safety valve has to be replaced to fix the issue.The link below is to the part you will need from a highly recommended company rated A+ with the Better Business Bureau. They offer a 100% money back guarantee, EVEN ON INSTALLED ELECTRICAL PARTS, for an entire year! They are the only company to allow returns on installed parts for a refund and offer a FULL ONE YEAR WARRANTY!
heres the link to order it GAS VALVE thanks and best wishes, Bryan