natural gas as alternative fuel

recently I have done one tuning for naturla gas car. It is our very first prototype engine with natural gas engine. The modification are as follows: 1. Use smart coil which run very high voltage and individually coil for each cylinder. 2. We use high pressure injector. Initially, to start the engine requires longer time because the gas inside the cylinder should reach cerain degree for ignition. At the moment we do not manage to start the engine yet. We tried to use gasoline for cranking only but failed.