High-pressure GDI pump with low-pressure bypass

A high-pressure fuel supply pump for an internal combustion engine fuel system that includes a high-pressure fuel injection apparatus, a low-pressure fuel injection apparatus, a low-pressure fuel supply pump, and a low-pressure feed line extending from the low-pressure fuel supply pump, said high-pressure fuel supply pump comprising:

• a plunger reciprocating in a pumping chamber and driven by a cam to generate high-pressure fuel;
• a low-pressure inlet connection receiving low-pressure fuel from the low-pressure feed line;
• a first low-pressure fuel flow path from the low-pressure inlet connection communicating with a damper chamber and a solenoid driven flow control valve assembly arranged to regulate a quantity of fuel pressurized by the plunger;
• a check valve between said low-pressure inlet connection and said first low-pressure fuel flow path, said check valve arranged to close against fuel flow toward the low-pressure inlet connection;
• a second low-pressure fuel flow path from the low-pressure inlet connection upstream of the check valve, said second low-pressure fuel flow path communicating first with a low-pressure seal chamber region around the plunger and then to a low-pressure fuel outlet;
• and
• wherein the second low pressure fuel flow path is fluidly separated from the damper chamber and the flow control valve between the low-pressure inlet connection and the low-pressure fuel outlet, and low-pressure fuel is circulated through the low-pressure seal chamber before leaving the fuel supply pump at the low-pressure fuel outlet.