Abstract: A diesel engine may have an electrically-actuated cold starting device in its inlet manifold, gravity fed with fuel from a reservoir interposed in a pipe for returning excess fuel from the injectors and injection pump to the vented fuel tank. If the pipe opens below the fuel level in the tank because the latter is full, or if oil is retained in the pipe by capillary action when the tank is not full, air cannot reach the reservoir to permit fuel flow to the device when required. The reservoir outlet to the tank therefore includes a restriction from which fuel emerges as a jet while the engine is running, and a vent hole within the zone containing the jet. The velocity of the jet carries fuel past the vent hole without any loss of fuel through the latter. When the engine is not running, the vent hole connects the reservoir to atmosphere.