Pinpoint Test C: DTC P1450 Excessive Vacuum Detected In The Fuel Tank

WARNING: This page is about a different car, the 2004 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Condition P1450 DTC set: more than -1.79 kPa (-7.2 inches H2O) over 30 seconds.

C1 CHECK FOR VISUAL CAUSES OF EXCESSIVE FUEL TANK VACUUM
- Check for kinks or bends in the fuel vapor hoses and tubes.
- Visually check the canister vent solenoid inlet port for contamination or foreign material.
- Check the canister vent solenoid for blockage or contamination.
- Is a concern with a hose, tube, connection or component visually evident?
  1. Yes : REMOVE any contamination or foreign material around fuel vapor hoses and tubes. REPAIR the hoses, tubes or components as necessary. After all visual concerns are repaired, GO to C2.
  2. No : GO to C2.
C2 CHECK FOR BLOCKAGE BETWEEN EVAP TEST PORT AND CANISTER VENT SOLENOID
- Disconnect and plug the EVAP return tube at the intake manifold.
- Connect the Evaporative Emissions System Leak Tester to the EVAP test port.
- Pressurize the EVAP system to 3.48 kPa (14 inches H2O).
- Does the pressure drop immediately?
  1. Yes : GO to C3.
  2. No : Go To PINPOINT TEST D: HISS WHEN OPENING FUEL CAP OR UNABLE TO REFUEL VEHICLE .
C3 CHECK FOR BLOCKAGE BETWEEN THE FUEL FILLER PIPE AND THE FUEL VAPOR CONTROL VALVE TUBE ASSEMBLY
- Connect the Evaporative Emission System Leak Tester to the fuel filler pipe.
- Pressurize the EVAP system to 3.48 kPa (14 inches H2O).
- Does the pressure drop immediately?
  1. Yes : GO to C4.
  2. No : Go To PINPOINT TEST D: HISS WHEN OPENING FUEL CAP OR UNABLE TO REFUEL VEHICLE .
C4 CHECK FOR FUEL TANK PRESSURE SENSOR PID WITHOUT PRESSURE APPLIED
- Disconnect the EVAP canister outlet tube from the fuel vapor control valve tube assembly.
  
  Fig 1: Locating Fuel Vapor Control Valve Tube Assembly
  Courtesy of FORD MOTOR CO.
- Key in ON position.
- Access PCM PID FTP V.
- Record the reading.
- Is PID FTP V reading between 2.40 and 2.80 volts?
  1. Yes : GO to C5.
  2. No : REFER to INTRODUCTION article to continue diagnosis.
C5 CHECK FOR STUCK OPEN EVAP CANISTER PURGE VALVE CONDITION AT IDLE
- Reconnect the EVAP canister outlet tube.
- Remove the plug from the EVAP return tube and reconnect the tube to the intake manifold.
- Verify that the fuel filler cap is correctly installed.
- Key in ON position.
- Access PCM PIDs FTP V and EVAPPDC.
- Start the engine and allow to idle.
- Monitor the FTP V and EVAPPDC PIDs.
- When PID EVAPPDC is zero, is PID FTP V reading below 2.40 volts?
  1. Yes : INSTALL a new EVAP canister purge valve. REFER to EVAPORATIVE EMISSION CANISTER AND PURGE VALVE . CARRY OUT an EVAP system leak test. REFER to EVAPORATIVE EMISSION SYSTEM LEAK TEST . If the system passes the leak test, CARRY OUT an evaporative emissions repair verification drive cycle. REFER to EVAPORATIVE EMISSION REPAIR VERIFICATION DRIVE CYCLE .
  2. No : CARRY OUT the EVAP system leak test. REFER to EVAPORATIVE EMISSION SYSTEM LEAK TEST . If the system passes the leak test, CARRY OUT the evaporative emissions repair verification drive cycle. REFER to EVAPORATIVE EMISSION REPAIR VERIFICATION DRIVE CYCLE .