Hi My JD combine has a CAV rotary pump which was rebuilt last year after it sheared it's head. Ran perfectly well all last season and the start of this, still perfect when running but starting had become a nightmare. It takes a starter motor frying length of time to start. Checked. No visible fuel runback from fillter (stanadyne) but fitted fuel one way valve anyway near fuel pump. Fuel pump fine (electric) good pressure and flow. New filter but old one crystal clear. Stopped and left parked in run position but no better. Fuel comes from the lower bleed but not upper. Left fuel tank cap off when stopped never noticed vacuum before. When you try to start it fires immediately but dies, then nothing for ages then a quick run then dies they another long churn and eventually starts and runs perfectly. Really getting nervous about this. I'm going to change the back plate for the filter and pipes but apart from that I'm out of ideas. Anyone?