Chart A-7, Fuel System Pressure Test: Notes

Fuel pump delivers fuel to fuel rail and fuel injectors, where fuel pressure is maintained at 35-42 psi (2.5-3.0 kg/cm² ) by pressure regulator. Excess fuel is returned to fuel tank. With engine stopped, fuel pump can be energized by applying battery voltage to fuel pump relay connector with a fused jumper wire. Fuel pump relay is located in fuse/relay block, on left side of engine compartment, near battery.

1. Release fuel pressure before disconnecting fuel lines. Wrap fuel line using shop towel before disconnecting fuel lines.
2. With engine idling, high manifold vacuum is applied to pressure regulator, lowering fuel pressure to about 25-30 psi (1.8-2.1 kg/cm² ).
3. Applying vacuum to pressure regulator should decrease fuel pressure.
4. If fuel pressure decreases quickly, it may be caused by: defective fuel pump check valve, fuel lines leaking, leaking pressure regulator or fuel injectors stuck open.
5. Fuel pressure less than 35 psi (2.5 kg/cm² ) may be caused by a defective pressure regulator or restricted fuel flow. Low fuel pressure may result in hard starting and poor driveability, and Code 44 may be set.
6. Restricting fuel return line allows fuel pump to obtain maximum fuel pressure. With battery voltage applied to fuel pump relay connector, fuel pressure should be greater than 60 psi (4.13 kg/cm² ).
7. Determines if high fuel pressure is caused by fuel line restriction or defective pressure regulator.