Fuel System - Testing Residual Pressure

Bulletin: P91-001

Section: PRODUCT

Dated: 01/21/91

Applicable to: USA, CANADA

SUBJECT:
EFI SYSTEM - TESTING RESIDUAL PRESSURE

The following information supplements that which is found in the Workshop Manual and should be used whenever diagnosing complaints of hard starting after a 10 to 30 minute shutdown or other similar hot starting complaints.

The tests are designed to measure leakage from the pressure regulator, fuel pump check valve and injectors.





SPECIFICATIONS





TOOLS REQUIRED

WORK PROCEDURE

- Connect the Hand Held Tester (HHT) with appropriate memory card to the vehicle serial link harness.

- Attach the fuel pressure gauge (and adaptor for 1991 Models) per the Workshop Manual, Sec. 19. OBSERVE CAUTIONS ON FUEL SPILLAGE.

- Prompt the HHT to fuel pump test.

- Operate the fuel pump with the HHT and observe fuel pressure - compare with specs. - engine not running.

- Start the engine and observe fuel pressure - compare with specs. - engine running.

- Shut off the engine and check residual pressure - maximum drop is 10 p.s.i. in one minute.

- If pressure drop is excessive do the following:

1. Operate fuel pump with HHT to build pressure - engine NOT running.

2. Shut off pump and immediately clamp off return line from the pressure regulator.

3. Observe pressure: Continues to drop - Go to Step 4.
Holds pressure - Replace pressure regulator and
retest.

4. Operate pump to build pressure and shut off.

5. Clamp off pressure hose from pump as follows:

1987-1990 - Before fuel filter in wheel arch
1991 - Remove access cover on loadspace floor to reach pressure hose (the pressure line is the left hand hose).

6. Observe pressure: Continues to drop - Go to Step 7.
Holds pressure - Replace fuel pump assembly.

7. Using the Workshop Manual as a guide, lift the fuel rail with injectors from the intake manifold - do not detach fuel lines.

8. Operate the fuel pump with the HHT - maximum leakage is 2 drops per minute per Injector - replace any with excessive leakage.

WARRANTY INFORMATION

Submit warranty claims as follows:

Service Type : WW
Repair Code : Code to Fault
Labor Operations :
Steps 1 - 6 : 195000 - 1.0 hr.
Steps 1 - 8 : 195000 - 2.0 hrs.