In one example, a system for a vehicle travelling on a surface is described. The system includes an engine with a cylinder. The cylinder includes a fuel injector that is supplied with gaseous fuel and liquid fuel by a fuel delivery system. The fuel injector is mounted in the vehicle such that the fuel injector inlet faces at least partially toward the road surface. The orientation of the fuel injector enables a quick transition from liquid fuel to gaseous fuel because the gaseous fuel can rise to the injectors and be preferentially injected. Further, various approaches are described from transitioning operation between gaseous and liquid fuel injection.