hi everybody, my missus has a landy 300TDI discovery. The last week its been getting to be a real bugger to start. It eventually starts but when it does sits at under 500rpm nearly staling. today i replaced the fuel filter and two of the glow plugs that werent working. I also drained the sedimentor. It ran fine for a couple of hours but then went back to not starting straight away, even when hot !! Could it be the 'fuel cut off switch' on the pump. is it worth me replacing this aswell or is there something im missing ???