Description And Operation
The fuel pump control module (3) is located on the body of the car (left side of fuel tank).
The engine control module (ECM) sends commands to the fuel pump control module through the wire from pin 57. The command that the fuel pump control module receives is type Pulse Width Modulated (PWM). Depending on the duty cycle, the ECM communicates to the fuel pump control module the way in which it should drive the fuel pump motor. The outcome is a low-pressure fuel pump that rotates at a number of revolutions (rpm) that varies in function of the PWM signal that the ECM sends to the fuel pump control module. The goal is to allow the LP low-pressure fuel pump to send the HP high-pressure fuel pump the fuel flow strictly necessary to meet the engine's demand for fuel.
In this way, the fuel quantity that the low-pressure pump must push is lowered, with a consequent reduction in the absorbed current. The lower current absorption by the LP low-pressure fuel pump results in a lower load on the generator (lowering engine fuel consumption).
At each "Key ON", the following actions take place:
- ECM activates the T10 relay.
- ECM processes the fuel pump control module signal in function of the engine coolant temperature and sends it to the fuel pump control module.
- The fuel pump control module supplies the fuel pump's power for a calibrated period of time.
- If the engine doesn't start, the ECM sets the fuel request to zero and deactivates relay T10.
During the starting phase (cranking) the following actions take place:
- ECM activates the T10 relay.
- ECM processes the PWM signal and sends it to the fuel pump control module.
- The fuel pump control module sends fuel supply to the fuel pump until the calibrated time elapses and fuel pressure reaches the minimum value to start the engine.
Depending on the engine operating point, the ECM calculates the engine's fuel requirement, refines it according to the coolant temperature and sends a Pulse Width Modulation (PWM) signal to the fuel pump control module. The latter, in function of the PWM signal received, commands the fuel pump to ensure the required fuel quantity in terms of flow and pressure. At this point, the ECM uses the temperature and pressure sensor to check if the requested target pressures are being reached along the low-pressure line. If it finds a deviation between "target" and "required", it will regulate it by "adjusting" the PWM signal previously sent to the fuel pump control module. The temperature control allows the ECM to prevent cavitation at the high-pressure pump inlet.