Mechanical Tests

WARNING:
While carrying out the mechanical tests on the fuel injectors, fuel will likely be spilled. Use all precautions to eliminate the possibility of fuel coming into contact with an ignition source. All testing should be done in a well ventilated area and the technician should wear safety glasses at all times. Carefully read the instructions provided with the fuel injection tester before starting the test.

CAUTION:
TestBook's pressure gauge adapter may be used only if the vehicle has been in the workshop overnight with engine completely cold.

NOTE:
The engine temperature should be lower than operating temperature in order to avoid irregular fuel pressure readings due to "Hot Soak" fuel vaporization. Remove fuel filler cap to lessen effect of a warm engine.

1. Attach LR7211 fuel pressure gauge to the fuel rail using adapter LR7272.

2. Energize the fuel pump. (See Operation Pride article 1-01 [TIB 12/03/96/US] for details.)

3. Bleed air from gauge.








4. Make a clean copy of the Fuel Injector Balance Test worksheet.

5. Allow pressure to stabilize and record fuel pressure on worksheet.

6. Shut off the fuel pump and verify that fuel pressure remains constant.

NOTE:
If pressure drops rapidly there are several possible causes:
^ The check valve in the fuel pump may be faulty
^ The fuel pressure regulator may be damaged
^ An injector may be leaking

To provide effective fuel control to the engine the injector must:

1. Not leak when it is closed

2. Open and close reliably

3. Allow the flow of a specified amount of fuel while open.

In order to accomplish these tasks not only does the injector need to be in good mechanical condition, with consistent fuel pressure, it must also receive the appropriate signals from the ECM. Use the following tests to confirm the injector system's operation

CAUTION:
Do not pinch the fuel lines on 97112 Discovery Advanced EVAPS vehicles built after VIN 546030/714242. These vehicles are fitted with special fuel lines which will be damaged if pinched. Vapor or fuel loss could occur. The Evaporative Emission System Test Equipment contains adapters which permit plugging of the fuel lines for test purposes. DO NOT CLAMP FUEL LINES.

7. If the fuel pressure remains stable, proceed with the injector balance test.

8. If the fuel pressure drops perform the following checks to determine the cause:

^ Pinch or plug the fuel line on the supply side.
^ If pressure holds the check valve in the fuel pump is bad.
^ If pressure continues to drop with supply side blocked, pinch or plug the return line.
^ If pressure then holds the fuel pressure regulator is the problem.