Low pressure fuel supply system for a fuel injection pump

Abstract

A low pressure fuel supply system supplies fuel which tends partially to solidify at low temperatures and whose viscosity increases with decreasing temperature, from a fuel tank along a supply line, through a filter, to a fuel injection pump. A fuel recirculating circuit for recirculating fuel warmed by the injection pump extends from a return outlet of the injection pump, along a path extending through the filter to the injection pump inlet. A permanent bleed pipe extends to the fuel tank from the portion of the recirculating circuit between the injection pump return outlet and the filter. The flow-resistance-determining dimensions of the permanent bleed pipe are such that the pipe presents increasing resistance to the flow of fuel therein with decreasing fuel temperature. It therefore carries little flow at low temperatures of the fuel therein, most of the warmed fuel from the injection pump return outlet being directed into the filter. Blockage of the filter by solidified portions of the fuel is thus avoided. Under normal operating conditions when the fuel temperature is higher, fuel flows more quickly through the permanent bleed pipe and so more of the warmed fuel is returned from the injection pump return outlet to the fuel tank, thus preventing overheating of the fuel and of the injection pump.