Diagnostic Aids

Symptoms for a blocked inlet path will include:
^ Inability to dispense fuel at anything above "trickle" rate, if that. Fuel evident at fill head.
^ Nozzle will shut-off virtually immediately, since no volume of fuel can be dispensed.
^ Suspect a stuck inlet check valve. Cheek for operation with siphon hose.

Symptoms for a blocked/restricted vent path include:
^ Pre-mature shut-off's of fill nozzle at medium to high flow rates.
^ Nozzle will shut-off after dispensing only 0.2-0.3 gallons (may be less with higher temperatures and/or higher RVP fuels). After a few second wait, this process can be repeated.

1. Connect Scan tool and look for DTC's P0446, P0440 or P1441.
2. Verify vent path.
3. Connect Scan tool and go into enhanced [1][2]EVAP tests to control vent solenoid and read fuel tank pressure sensor.
^ Normal sensor voltage is 1.3 to 1.7 volts. It will decrease with rising tank pressure.
^ If voltage drops rapidly below this value towards 0.2-0.3 volts during refueling this is indication that the major vent path is blocked.
^ Check vent path from [1][2]EVAP vent solenoid backwards to isolate problem component (vent solenoid, vent pipe/hose, canister, FLVV (Fill Limit Vent Valve), etc.