Do you have electronic fuel control? If so check the electronics are working properly. I once ran into a no fire condition on a JD6910 and it mimiced no fuel perfectly ,fooling the mechanic. The real problem was the electronic fuel control had a partial failure and was not lettting fuel through even though fuel was primed and at the injectors. NZ$9200 was spent overhauling the fuel injection pump. A waste of time, and we still had to buy a replacement ecu. grrrrrr