CHART A-7, FUEL SYSTEM PRESSURE TEST (EXCEPT GSi): Notes

Fuel pump delivers fuel to fuel rail and injectors. System pressure is controlled from 35-38 psi (2.5-2.7 kg/cm² ) by the fuel pressure regulator. Excess fuel is returned to fuel tank. When engine is stopped, pump can be energized by applying battery voltage to test terminal, located in engine compartment.

1. Use Pressure Gauge (J-34730-1). Wrap shop towel around fuel pressure tap to absorb fuel leakage when installing gauge. Pressure should not leak down after fuel pump is stopped if system is functioning correctly.
2. With engine idling, manifold pressure (vacuum) is high and, when applied to fuel pressure regulator diaphragm, will result in a lower fuel pressure of about 30-35 psi (2.1-2.5 kg/cm² ).
3. The application of vacuum to the pressure regulator should result in fuel pressure drop.
4. Pressure leak down may be caused by one of the following: in-tank fuel pump check valve not holding, pump coupling hose leaking, fuel pressure regulator valve leaking or injector is stuck open.
5. A pressure of less than 38 psi (2.7 kg/cm² ) may be caused by any of these problems:
   • Regulated pressure too low. System will be running lean and may set Code 25. A cold hard start and overall poor performance is possible.
   • Restricted fuel flow is causing a pressure drop. Normally, a vehicle with a fuel pressure loss at idle will not be driveable. However, if pressure drop occurs only while driving, engine will surge and then stop as pressure begins to drop rapidly.
6. Restricting the fuel return line will allow fuel pump to build pressure greater than regulated pressure. When battery voltage is applied to FP terminal on check connector, pressure should be greater than 65 psi (4.6 kg/cm² ).
7. This test determines if the high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.