Internal combustion engine and method for operating an internal combustion engine

A method, comprising:

• operating with injection of LPG pressurized at a rail via a pump through only a first injector to a cylinder;
• deactivating the pump and subsequently increasing LPG pulse width with continuing LPG injection through the first injector;
• subsequently coupling a CNG source to the rail while continuing injection with the first injector;
• and
• responsive to reaching a condition, deactivating the first injector and operating with only the second injector injecting to the cylinder.

An engine method, comprising:

• operating with injection of LPG pressurized at a rail via a pump through only a first injector to a cylinder;
• deactivating the pump and subsequently gradually increasing LPG pulse width with continuing LPG injection through the first injector while rail pressure decreases with the pump still deactivated and without injection from a second injector to the cylinder;
• subsequently coupling the CNG source to the rail via a switching valve while continuing injection with the first injector;
• responsive to reaching a threshold rail pressure, deactivating the first injector and operating with only the second injector injecting CNG to the cylinder, a pulse width of the second injector adjusted to account for continued decreasing of the rail pressure and maintaining a desired air-fuel ratio in the cylinder;
• responsive to a request for LPG fuel and discontinuing of CNG injection, reactivating the fuel pump and simultaneously switching the switching valve;
• and
• discontinuing injection from the second injector and delivering fuel only via the first injector responsive to fuel rail pressure reaching a threshold and based on an estimate of a fuel state in the rail.