Fuel system having isolation valves between fuel injectors and common drain conduit

A fuel injector comprising:

• an injector body having a high pressure nozzle supply passage, a check control chamber, and a low pressure outlet formed therein;
• a direct operated nozzle check;
• an injection control valve assembly;
• and
• an isolation valve assembly including an isolation valve member movable between a closed position blocking the injection control valve assembly in the one of the plurality of fuel injectors from the common drain conduit, and an open position, and a biaser biasing the isolation valve member toward the closed position.

An isolation valve assembly for a fuel system comprising:

• a valve body positionable in a fuel injector, the valve body having formed therein a low pressure outlet, a drain path structured to fluidly connect to a check control chamber for an outlet check in the fuel injector, and a valve seat positioned fluidly between the drain path and the low pressure outlet;
• an injection control valve assembly including an injection control valve member movable between a closed control valve position blocking the valve seat, and an open control valve position;
• an isolation valve member positioned fluidly between the injection control valve assembly and the low pressure outlet and movable between an open isolation valve position and a closed isolation valve position;
• and
• a biaser biasing the isolation valve member toward the closed isolation valve position, such that movement of the isolation valve member from the closed isolation valve position to the open isolation valve position in response to a pulse of fluid pressure through the valve seat is in opposition to a biasing force of the biaser.