Part 2 of 3

Circuit Description
The Fuel Pump delivers Fuel to the Fuel Rail and Injectors, where the system pressure is controlled from 280 to 320 kPa (41 to 46 psi) by the Fuel Pressure Control Valve. Excess fuel is returned to the Fuel Tank. When the Engine is stopped, the Pump can be energized by jumping the Fuel Pump Relay Connector with a fused jumper.




Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

5. Pressure less than 280 kPa (41 psi) may be caused by one of two problems.
- The regulated Fuel pressure is too low. The system will be running lean and may set Diagnostic Trouble Code 44. Also, hard cold starting and overall poor performance is possible.
- Restricted flow is causing a 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 surge and then stop as pressure begins to drop rapidly.

6. Restricting the Fuel Return Line allows the Fuel Pump to build above regulated pressure. When Battery positive voltage is applied to the Fuel Pump relay, 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 Fuel Pressure Control Valve problem.

NOTE: Fuel System is under pressure. To avoid Fuel spillage, refer to field service procedures for testing or repairs requiring disassembly of Fuel Lines or Fittings. Refer to part 3 of 3 of this chart.