Air in fuel line n bubbling in fuel tank

[therefused]

I noticed today, wen under the bonnet if I rev the engine there will be a air bubble that goes down the fuel line between the pump and filter, is this normal or do I have a leak?

When I switch off the engine I can hear bubbling or fuel running back to the tank?

[underground375]

have you un done the bleed screw at the fuel filter housing to release the air? I would check the housing also in case air in getting in. When I changed my fuel filter it come with a rubber ring to seal the cap, but after a few weeks the ring mine come with failed =\ None of that, I would check all fuel lines.

[therefused]

Yeh I've bled it fine, if I pump the grenade it will go hard then soft again fairly quickly (without starting the engine)

I've replaced the fuel filter a few weeks ago, it was one of them plastic ones, the one I took out was metal so I'm not surprised if the plastic one has failed cuz it was a pattern part cheap quality.