Tata Safari diocor lx problem[engine cranks and not start]

[adil]

I have a tata safari dicor lx diesel.Sometime problem happens the engine cranks but not start.We have shown them to service center it was not happening before them as it happens sometime they checked everything and all was ok.
But same problem comes sometime that engine cranks but not start so someone
suggested us to inject little petrol in pipe

http://i51.tinypic.com/29azf3t.jpg


After doing this engine starts.
though the problem happens sometime only but we are not able to rectify the cause please help help.


thanks
adil