Alero L4-144 2.4L DOHC VIN T SFI (2000)
Diagnostic Chart (Part 3 Of 3)
CIRCUIT DESCRIPTION
When the ignition switch is turned on, the Powertrain Control Module (PCM)will turn on the in-tank fuel pump. The in-tank fuel pump will remain on
as long as the engine is cranking or running and the PCM is receiving reference pulses. If there are no reference pulses, the PCM will turn off the
in-tank fuel pump after 2 seconds, or 2 seconds after the engine stops running. The in-tank fuel pump is an electric pump within an integral reservoir.
The in-tank fuel pump supplies fuel through an in-line fuel filter to the fuel rail assembly. The fuel pump is designed to provide fuel at a pressure
above the pressure that is needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail assembly, keeps the fuel available to the fuel
injectors at a regulated pressure. The unused fuel is returned to the fuel tank by a separate fuel return pipe.
TEST DESCRIPTION
The numbers below refer to step numbers on the diagnostic table.
2. In order to relieve the fuel pressure, go to Fuel Pressure Relief Procedure. When the ignition switch is on and the fuel pump is running, the fuel
pressure indicated by the fuel pressure gauge should be 358-405 kPa (52-58 psi). See:
3. A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more of the following areas:
^
The fuel pump check valve
^
The fuel pump flex pipe
^
The fuel injectors
5. Fuel pressure that drops-off during acceleration, cruise, or hard cornering may cause a lean condition. A lean condition can cause a loss of power,
surging, or a misfire. You can use a scan tool in order to diagnose a lean condition. If an extremely lean condition occurs, the oxygen sensors will
stop toggling. The oxygen sensor output voltages will drop to less than 500 mV. Also, the fuel injector pulse width will increase.
8. When the engine is idling, the manifold pressure is low (high vacuum). This low pressure (high vacuum) is applied to the fuel pressure regulator
