Pulsating fuel return pipe

Hello,

Can anyone assist with Discovery 300tdi M plate?

I have recently had new head gasket/timing belt etc. Vehicle starts but fuel return pipe on injector pulsates with excessive pressure and pipe come away from injector. Its also had new lift pump and bled through. I also notice pressure when releasing fuel cap.

Any ideas?

Marc.

Is the breather pipe blocked on the fuel tank? That was the cause of my hissing when I opened the fuel tank.