Fuel pump

A high-pressure fuel pump for pressurizing fuel and pumping the fuel to an accumulation chamber, the high-pressure fuel pump comprising:

• a housing having a compression chamber, a discharge passage, which is configured to communicate the compression chamber with the accumulation chamber, and a return passage, which is configured to communicate the discharge passage at a side of the compression chamber with the discharge passage at a side of the accumulation chamber;
• a plunger axially movable in the housing for pressurizing fuel, which is drawn into the compression chamber;
• a discharge valve accommodated in the discharge passage and configured to open to supply fuel from the compression chamber to the accumulation chamber when pressure in the compression chamber becomes higher than or equal to predetermined pressure;
• a relief valve having a first valve element accommodated in the return passage, the relief valve configured to close unless pressure in the accumulation chamber becomes higher than a first pressure, which is higher than pressure in a normal operation, the relief valve further configured to open to release pressure in the accumulation chamber to the compression chamber when pressure in the accumulation chamber becomes higher than the first pressure to be in an abnormal high-pressure condition;
• and
• a pressure holding mechanism having a fuel passage, which is located in the first valve element and configured to communicate the return passage at a side of the compression chamber with the return passage at a side of the accumulation chamber when the relief valve closes,
• wherein the pressure holding mechanism further includes a second valve element, which is accommodated in the fuel passage, and
• the pressure holding mechanism is configured to close to hold pressure in the accumulation chamber when pressure in the accumulation chamber decreases to a second pressure, which is lower than the pressure in the normal operation.