Fuel System Diagnosis

Fuel System Diagnosis

Circuit Description

When the ignition is turned ON, the powertrain control module (PCM) supplies power to the in-tank fuel pump, by energizing the fuel pump relay. This action supplies battery voltage to the fuel pump via the fuel pump module. The in-tank fuel pump remains ON as long as the engine is cranking or running and the PCM receives crankshaft reference pulses. If there are no reference pulses, the PCM turns the in-lank fuel pump OFF, 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running. The electric fuel pump is incorporated into the modular fuel pump and sender assembly design and is located inside the fuel tank. The fuel pump supplies fuel through a fuel filter, also located in the modular fuel pump and sender assembly, through the fuel feed pipes, to the fuel rail assembly. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. The fuel pressure regulator, located in the base of the modular fuel pump and sender assembly, keeps the fuel available to the fuel injectors at a regulated pressure. When the fuel pressure rises above the pressure regulator calibration, the pressure is relieved, with excess fuel exhausted into the modular fuel pump and sender assembly reservoir.

Test Description

Fuel System Diagnosis 1 Of 2:

Fuel System Diagnosis 2 Of 2:

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

3. This step determines whether the fuel pump can provide fuel within the correct regulated pressure range.

4. This step tests that the fuel system can maintain fuel pressure with the pump Off. A fuel pressure drop of more than 34 kPa (5 psi) within the specified time indicates a leak in the fuel system.

11. This step tests for a restriction in the fuel system.