Two stage valve with conical seat for flow shut-off and spool knife edge for metering flow control

A system for metering fuel to at least one fuel pumping chamber, comprising:

• a fuel supply;
• a metering valve having a first opening in flow communication with the fuel supply and a second opening in flow communication with the at least one pumping chamber, the valve further including a solenoid and a spool mounted within a housing for reciprocal movement between a plurality of opened positions, wherein fuel flows through the valve from the fuel supply to the at least one pumping chamber, and a closed position, wherein fuel is substantially prevented from flowing through the valve;
• and
• an ECM configured to provide signals to the solenoid to position the spool into the plurality of opened positions and the closed position;
• wherein the spool includes a tip surface at one end that engages a seating surface to prevent fuel flow when the spool is in the closed position, a metering edge that cooperates with the second opening when the spool is in the plurality of opened positions to meter fuel flowing through the valve, and
• wherein the valve includes a flow path between a first chamber disposed between the first opening and the second opening and a second chamber disposed adjacent another end of the spool, the flow path permitting fuel flow between the first chamber and the second chamber to substantially equalize pressure exerted by the fuel on each end of the spool.