Low evaporative emission fuel system depressurization via solenoid valve

A fuel delivery system for an engine, comprising:

• a fuel tank to contain a volume of fuel;
• a fuel pump in fluid communication with the fuel tank to pressurize the fuel;
• a fuel rail in fluid communication with the fuel pump to receive the pressurized fuel;
• an injector in fluid communication with the fuel rail to supply the pressurized fuel to the engine;
• a first valve in fluid communication with the fuel rail to maintain the fuel in a pressurized state;
• a second valve in fluid communication with the fuel rail to relieve the pressurized state of the fuel when the engine is not operating;
• a solenoid valve, provided between a pressurized side of the fuel delivery system and the fuel tank, being operably opened during key-on and the engine is off to reduce fuel pressure until the injector is open, and after an ignition key has been turned from an on position to an off position to drain fuel into the fuel tank;
• and
• a fuel orifice in fluid communication with the fuel rail, the fuel orifice being positioned upstream from the solenoid valve.

A method for minimizing fuel leakage in a fuel delivery system of an engine while the engine is off, the fuel delivery system comprising a fuel tank containing a volume of fuel, a fuel pump, a fuel rail, an injector, a first valve, a second valve, a solenoid valve, and a fuel orifice, the method comprising:

• determining whether an ignition key is turned to an on position;
• determining whether the solenoid valve is open, and closing the solenoid valve if determined to be open;
• determining whether a fuel pressure has exceeded a target level;
• opening the solenoid valve and increasing a flow of the fuel pump when the fuel pressure has exceeded the pressure target value;
• determining whether a fuel flow of the injector is above a flow speed;
• and
• closing the solenoid valve and reducing the fuel pump flow once the injector fuel flow is above the flow speed.

A method for minimizing fuel leakage in a fuel delivery system of an engine while the engine is off, the fuel delivery system comprising a fuel tank containing a volume of fuel, a fuel pump, a fuel rail, an injector, a first valve, a second valve, a solenoid valve, and a fuel orifice, the method comprising:

• determining whether an ignition key is turned to an off position;
• evaluating a fuel temperature in the fuel rail via one of measurement and inference;
• computing a minimal positive pressure, the minimal positive pressure enabling the fuel delivery system to minimize fuel leakage for a substantially volatile fuel at the evaluated temperature;
• opening periodically the solenoid valve when the fuel pressure has exceeded a predetermined pressure value, the predetermined pressure value being greater than the minimal positive pressure.

A fuel delivery system for an engine, comprising:

• a fuel tank to contain a volume of fuel;
• a fuel pump in fluid communication with the fuel tank to pressurize the fuel;
• a fuel rail in fluid communication with the fuel pump to receive the pressurized fuel;
• an injector in fluid communication with the fuel rail to supply the pressurized fuel to the engine;
• a first valve in fluid communication with the fuel rail to maintain the fuel in a pressurized state;
• a second valve in fluid communication with the fuel rail to relieve the pressurized state of the fuel when the engine is not operating;
• a solenoid valve, provided between a pressurized side of the fuel delivery system side and the fuel tank, being operably opened during key-on and the engine is off to reduce fuel pressure until the injector is open, and after key-off to drain fuel into the fuel tank;
• a fuel orifice in fluid communication with the fuel rail, the fuel orifice being located upstream from the solenoid valve;
• and
• a third valve in fluid communication with the fuel rail, the third valve being located upstream from the fuel orifice.