To perform re-circulation of a part of a flow of surplus fuel from a fuel injection pump.

A fuel circuit 10 for a fuel system 12 comprises a fuel tank 14; a fuel injection system 16; a fuel suction pump 22; and a fuel strainer assembly 20. The fuel circuit contains fuel passages 44 and 66 to re-circulate a flow of surplus fuel from the outlet 50 of a fuel injection pump to the inlet of a fuel injection pump. A flow of surplus fuel pressurized by the fuel injection pump is used as a fuel feed source for suitable and low pressure fuel in a fuel tank. According to an amount of heat generated by a fuel injection system and a fuel suction pump and an estimated ambient temperature condition, a fuel circuit includes a heat-exchanger 56 from sole fuel to air, a heat-exchanger 60 from fuel to cooling liquid, or a heat-exchanger 62 from cooling liquid to air. Circulation pumps 64 and 68 for the fuel passage 66 and a cooling liquid line 70 are used to promote removal of the heat of two heat-exchanger systems.