Part 2 of 4

Chart A-7:

Fuel Flow Circuit:

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. Excess fuel pressure is bypassed back 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. Improper fuel system pressure may contribute to Codes 44 or 45, cuts out which may feel like an ignition problem, hesitation loss of power or cause a "Cranks But Won't Run" condition.

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

5. Pressure less than specifications falls into two areas:

^ Regulated pressure less than specifications; the amount of fuel to injectors is OK, but pressure is too low, The system will be lean running 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 of less than 165 kPa (24 psi) 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. DO NOT allow fuel pressure to build above regulated pressure. When battery voltage is applied to the pump test terminal, pressure should be above 325 kPa (47 psi) as the valve in the return line is partially closed.

NOTE: DO NOT allow pressure to exceed 414 kPa (60 psi), as damage to the regulator may result.

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