Fuel tank breather hose noise

Hi All,

My Dads car has been running rough for awhile. I was 100% sure a new MAF was going to fix the problem, but now  I'm not that sure.

I was sitting in the car after about a 15-min journey, turned the ignition on and i hear this noise, like a HGV reversing in  the distance. So i put no pass on it. Then i drove about 500m and i hear it again. So i popped the bonnet and the noise is coming from the charcoal canister. I put my ear up to the canister, and its the fuel tank breather hose end. I removed the end of the breather hose and i could hear the noise clearly.

So, is the fuel pump knackered? or any ideas?

Cheers