Checking for blockage between the fuel tank pressure sensor and the fuel tank

HINT: If "small leak" is detected after a completed quick test of the fuel tank system, it may in certain cases be due to a blockage between the fuel tank pressure sensor and the fuel tank.

HINT: The method below is used to determine whether the detection of "small leak" after completed quick tests is caused by a blockage between the fuel tank pressure sensor and the fuel tank. It can be carried out by running the test with the fuel tank filler cap removed. Normally a "large leak" is detected with the fuel tank filler cap removed. If a "small leak" is detected with the fuel tank filler cap removed it indicates a blockage between the fuel tank pressure sensor and fuel tank.

HINT:

NOTE:

If the EVAP canister fills with the fuel vapor the test is interrupted. The EVAP canister fills with fuel vapor faster if the evaporative emission system (EVAP) valve is operating and the fuel tank filler cap is removed. Start the quick test directly after engine start and do not let the engine run at idle speed for longer than necessary.

Fig 1: Engine Start Verification

Courtesy of VOLVO CARS OF NORTH AMERICA.

Remove the fuel tank filler cap
Engine idling
Start the quick test with the fuel tank filler cap removed.
In particular check the fuel tank pressure (red line) when the "large leak" test is running.

If a "large leak" is detected with the fuel tank filler cap removed, the most likely cause is leakage. Continue fault-tracing according to "small leak".

If the test is cancelled or "small leak" is detected with the fuel tank filler cap removed and the fuel tank pressure (red line) falls more slowly than normal during the test it may be due to a blockage in the hose or hose terminal between the tank and the fuel tank pressure sensor. This can be fault-traced by removing the hoses to the evaporative emission (EVAP) system components one at a time and carrying out a quick test between each operation. If a "large leak" is detected after the quick test when the hose has been disconnected the fault is in the direction of the airflow (calculated from the hose that has been disconnected).

HINT: The direction of airflow during a quick test can be calculated from the fuel tank: fuel tank, evaporative emission system (EVAP) canister, evaporative emission system (EVAP) valve. The fuel tank pressure sensor measures the pressure in the hose between the fuel tank and the evaporative emission system (EVAP) canister.

HINT: If the hose for the EVAP canister is detached from the fuel tank and a "large leak" is detected, there is a blockage in the tank hose terminal.

Remedy as necessary.

Reset all the components. Carry out a quick test of the tank system before the car is delivered to the customer.

Select a suitable alternative to continue:
1. Continue "small leak" fault-tracing
  Refer to Small leak
2. Finish.
  OKAY: Troubleshooting has been completed.
Fig 2: Identifying VCT2000 Diagnostic Tool Symbol In VIDA
Courtesy of VOLVO CARS OF NORTH AMERICA.

Fig 3: Identifying Fuel Tank, Evaporative Emission System (EVAP) Canister And Evaporative Emission System (EVAP) Valve
Courtesy of VOLVO CARS OF NORTH AMERICA.