DUAL FUEL SYSTEM AND OPERATING STRATEGY METERING FUEL VIA VARIED FUEL PUMP OUTPUT

A dual fuel system includes a first fuel supply of a first fuel, a second fuel supply of a second fuel, and a variable-output fuel pump. A fuel injector in the dual fuel system includes a combined-fuel outlet passage, a nozzle check movable to open and close the combined-fuel outlet passage to nozzle outlets, and a check valve positioned at least partially in a first fuel passage connected to the first fuel supply by way of the variable-output fuel pump. The first fuel may include a compression-ignition fuel and the second fuel may include an alcohol fuel. Varying output of the fuel pump during an off-cycle of a cam actuating a plunger in the fuel injector meters the first fuel to the fuel injector for forming a fuel charge for injection. Related apparatus and methodology is also disclosed.