Yeah for the sake of it id remove the lines and give them a good visual could be kinked/squashed somewhere or split and the air is escaping somewhere. Ive had a similar problem and my only option was to feed some thin fencing wire down the line. At the end of the day fuel line isnt that dear and you can use your old fuel line as a template to bend up another one with a cheap ebay hand held pipe bender. Ebay also sells rolls of fuel line pretty reasonably priced.