Service Procedure

Attempt to duplicate stall concern with the New Generation Star (NGS) Tester connected to the vehicle. Monitor Parameter Identification Display (PID) for evaporative emission purge duty cycle (EVAPPDC), both front Heated Exhaust Gas Oxygen (HEGO) sensors (02S11 and 02S21), and long and short fuel trim (SHRTFT1 and LONGFT1). Normal operating range for the long and short fuel trim is +/- 10%. If, during the stall, the engine goes rich, then lean (the SHRTFT1 is greater than +/- 15% for a length of time), and the Vapor Management Valve (VMV) is open (from 30% to 100%) perform the following:

1. Remove the evaporative emission canister from the vehicle.

2. Inspect the canister for water or liquid fuel contamination. If water or liquid fuel is found in the canister, the Canister should be replaced (F5VY-9D653-C).

3. Verify the plastic screens and green foam that prevent the carbon pellets from escaping the canister are present. Correct position of the screens is close to the top of the canister; the grid is readily visible.

4. Inspect all of the hoses/tubes that run from the canister to the fuel tank and from the canister to the VMV to ensure they are not damaged, kinked or restricted. Repair as required.

5. If black carbon dust is found inside the vacuum line between the canister and the VMV, the Vacuum Line (F1AZ-9324-A) and VMV (F5AZ-9C915-A) should be replaced.

6. Inspect the hose fittings that connect to the canister. The 0-ring seals should be inspected for any cuts or other damage. Leaks at the 0-rings can allow water to enter the canister. Water inside the canister will cause the carbon pellets in the canister to degrade.

7. Remove the fuel tank from the vehicle. Refer to Page 10-01A-8 of the 1996 Town Car Service Manual.

8. Carefully inspect the wiring on the fuel pump/sender assembly for any signs of abrasion or damage. Repair the wiring as required.

9. Remove the Vapor Control Valve (VCV) assembly from the fuel tank.

10. Install new VCV (F6AZ-9C047-BA) onto the fuel tank.

NOTE
THE NEW VCV DOES NOT REQUIRE THE SIGNAL LINE CONNECTION TO THE FUEL FILLER TUBE.

11. Remove the fuel tank filler pipe from the vehicle.

12. Install new Filler Pipe (F6VZ-9034-DA) into vehicle.

13. Remove the old fuel tank strap studs from the underbody and discard. The studs cannot be reused.

14. Install the fuel tank into the vehicle. Take extra care to ensure that none of the fuel lines, hoses, or wiring are pinched between the tank and the body.

NOTE
THE FUEL TANK STRAP STUDS ARE A 2-PART ASSEMBLY. THE NUT ON THE STUD IS USED TO INSTALL THE STUD INTO THE BODY. WHEN INSTALLING THE FUEL TANK, THE NEW STUDS ARE INSTALLED BY: 1) INSERTING THE STUD THROUGH THE FUEL TANK STRAP. 2) THREADING THE STUD INTO THE J-NUT IN THE BODY. 3) TIGHTENING THE STUD. THE STUD WILL THREAD ITSELF INTO THE J-NUT AND STOP, THEN THE NUT ON THE STUD WILL BEGIN TO TIGHTEN DOWN ON THE FUEL TANK STRAP. WHEN THE NUT IS FULLY TIGHTENED, THE EXCESS LENGTH OF THE STUD MUST BE BROKEN OFF AT THE GROOVE MACHINED INTO THE STUD. REFER TO PAGE 10-01A-8 AND 9 OF THE SERVICE MANUAL FOR DETAILS.

15. Inspect the fuel pump/sender ground wire connection (G401). This is located in the trunk of the vehicle on the driver's side near the inertia switch. A poor ground connection can result in reduced fuel pressure and volume.

16. Reprogram the PCM to the new level calibration. The new calibration is less sensitive to sudden changes in the fuel vapor flow during decelerations.