I had a similar problem with a fuel cock. It indicated that it was opening (visual indicator) during the start sequence but the engine would not light off properly (just a slight rise in T-4 which indicated that the micropump and ignitors were working). Just to check it I removed the fuel cock and manually turned the fuel valve to open and the engine lit off OK. I had to put in another fuel cock and it works fine now.

thank you sir for the responce..
I will try to remove the fuel cock and open up only the valve.
And try another attempt.. good day!!