Circuit/System Description

Low Pressure System 

After the vehicle has been powered Off for at least 2 min and the ignition is turned On, the engine control module (ECM) sends a signal via the fuel pump primary relay circuit to the fuel pump driver control module. The fuel pump driver control module enables the fuel pump for 30 s or continuously when the engine is running. The fuel pump driver control module actuates the brushless fuel pump by means of a high power three phase signal and controls the fuel pump speed according to serial data signals received from the ECM containing the desired fuel pump speed.

The fuel tank stores the fuel supply and the brushless fuel pump, pumps fuel from the fuel tank through the fuel filter/heater element housing, which contains the water separator, water in fuel sensor, fuel heater element, fuel temperature sensor, and fuel filter element. The fuel pressure is sensed by the fuel pressure sensor and then delivered to the high-pressure pump.

The fuel return system uses the unused return fuel to cool and lubricate the fuel injectors and fuel injection pump. If the high side fuel pressure becomes excessive, fuel pressure regulator 2 releases the fuel into the fuel return system. The returned fuel travels through the fuel return lines and fuel cooler to the fuel tank.

During a cold start, in order to warm the fuel the high pressure pump operates at full output and the pressure in the rail is regulated by fuel pressure regulator 2. This mode is also active during fuel injection cut-off. When in this mode, the fuel return line can flow up to 230 l/h (60.8 g/h).