Although it is a dig, but I just saw the thread now and after reading all the replies I though that I had to answer
Well the problem in starting in not due to any wiring issue but its the coil of CNG kit that becomes weak and when hot offers more resistance than is required so result is that kit cannot get proper current supply and does not start.
Now there are 2 options
1 Get the coil changed and enjoy the ride
2 Install a relay and do the juggar so that current supply increases.
Personally I would go for option although option is cheap but by doing so the coil will permanently want more current to start and not start without relay anymore+Plus there is also risk that car may not start if relay fails and believe I had a bolan and on 2 occasions relay got failed so a big hassle.