Part 2 of 2

Fuel System Pressure Test (Part 2 of 2):

Fuel System Circuit Diagram:

CIRCUIT DESCRIPTION:

The fuel pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled to 245 to 256 kPa (35 to 38 psi). Excess fuel pressure is returned to the fuel tank. When the engine is stopped, the pump can be turned "ON" by applying battery voltage to the test terminal located in the engine compartment.


TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.


5. Pressure less than 245 kPa (35 psi) falls into two areas:

^ Regulated pressure; The amount of fuel to injectors is OK but pressure is too low. The system will be running lean and may set Code 44. Also, possible hard starting cold and overall poor performance.

^ Restricted flow causing pressure drop; Normally, a vehicle with a fuel pressure loss at idle will not be driveable. However, if the pressure drop occurs only while driving, the engine will normally surge then stop as pressure begins to drop rapidly.

6. Restricting the fuel return line allows the fuel pump to develop its maximum pressure (dead head pressure). When battery voltage is applied to the pump test terminal, pressure should be above 450 kPa (65 psi).

7. This test determines if the high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.