Part 1 of 2

Chart A-7 (1 Of 2):

Wiring Diagram for Chart A-7 - Fuel System Pressure Test:

CIRCUIT DESCRIPTION:

An electric fuel pump, attached to the fuel level meter assembly (inside the fuel tank) pumps fuel through an in-line filter to the fuel rail assembly. The pump is designed to provide fuel at a pressure above the regulated pressure needed by the injectors. A pressure regulator, an integral part of the fuel rail assembly, keeps fuel available to the injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate line. The fuel pump test terminal is located in the engine compartment. When the engine is stopped, the pump can be turned "ON" by applying battery voltage to the test terminal. Improper fuel system pressure may contribute to one or all of the following symptoms:

^ Cranks but won't run.
^ Code E044 or E045.
^ Cuts out, may feel like ignition problem.
^ Hesitation, loss of power, or poor fuel economy.

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

1. Use pressure gage J-34730-1. Wrap shop towel around the fuel pressure tap to absorb any small amount of fuel leakage that may occur when installing the gauge. With ignition "ON," pump pressure should be 284-325 kPa (41-47 psi). This pressure is controlled by spring pressure and throttle body vacuum within the pressure regulator assembly. Pressure should not leak down after the fuel pump is shut "OFF."

2. When the engine is idling, the throttle body vacuum is high and is applied to the fuel regulator diaphragm. This will offset the spring and result in a lower fuel pressure (approximately 21-69 kPa (3-10 psi).

3. The application of 12-14 inches of vacuum to the pressure regulator should result in a fuel pressure drop of at least 21-69 kPa (3-10 psi).

4. Pressure that leaks 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.
- Injector sticking open.

FUEL PRESSURE CHECK:

CAUTION: To reduce the risk of fire and personal injury, it is necessary to relieve the fuel system pressure before servicing fuel system components. A small amount of fuel may be released when disconnecting the fuel lines. Cover fuel line fittings with a shop towel before disconnection, to catch any fuel that may leak out. Place towel in approved container when disconnect is completed. DO NOT pinch or restrict nylon fuel lines to avoid severing, which could cause a fuel leak.

NOTE: If nylon fuel lines become kinked, and cannot be straightened, they must be replaced.

1. Disconnect the negative battery terminal.
2. Loosen fuel filler cap to relieve fuel tank pressure. (DO NOT tighten at this time).
3. Connect fuel pressure gauge to fuel pressure connection. Wrap a shop towel around fitting while connecting gauge to avoid spillage.
4. Place bleed hose into an approved container and open valve to bleed system pressure.
5. Locate engine compartment fuel feed and return line quick-connect fittings.
6. Grasp both ends of one fitting, twist female end 1/4 turn in each direction to loosen any dirt in fitting. Repeat for other fitting.
7. Using compressed air, blow dirt out of quick-connect fittings.
8. Choose correct tool from separator tool set and insert tool into female end of connector, then push inward to release male connector. Repeat for other fitting.

CAUTION: Safety glasses must be worn when using compressed air, as flying dirt particles may cause eye injury.

Continued on CHART A-7 (Part 2 of 2).