Abstract: A fuel system for a diesel engine includes an air purging system for venting trapped air to a vent line connected to a fuel tank and an emergency shut-down system for providing a fail-safe shut-down of the engine when fuel is low. The air-purging system comprises a device defining a float chamber having an air outlet communicating with the vent line, a fuel inlet, and a fuel outlet. A float is disposed in the chamber and is adapted to move between a normal first position closing the air outlet, an emergency intermediate second position opening both the air and fuel outlets, and a shut-down third position opening the air outlet and closing the fuel outlet. The emergency shut-down system includes electronic and pressure sensitive switches, warning lights, and an auxiliary fuel pump to monitor and control the shut-down and restart modes of engine operation. The air purging system is adapted to function independently of the emergency shut-down system.