Part 1
Leak diagnostic
Safety
First read Safety regulations for handling fuel Safety Regulations for Handling Fuel.
Continue - Checking wiring and terminals
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Checking wiring and terminals
Check that the fuel tank filler cap is correctly secured. Check that its seal is intact.
Then check the hoses and the hose connectors at the EVAP canister. Check the EVAP canister shut-off valve. Check the fuel tank.
Remedy as necessary.
Carry out a quick test of the fuel tank system.
Continue - General information about testing the fuel tank system
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General information about testing the fuel tank system
The engine control module (ECM) has a built-in function to quickly check the tank system for leaks. Upon function activation, the control module determines whether the tank system and all of its components and hoses are fault-free or have leaks. Conditions for the test are:
- Engine speed < 3500 rpm.
- Engine temperature 30 °C.
- Normal battery voltage.
- Quantity of fuel in the tank < 60 litres.
- Height above sea level < 2500 m.
- Fuel evaporation is not too high (increased fuel evaporation increases pressure in the tank system).
The amount of fuel evaporation permitted varies depending on the leakage test. Higher fuel evaporation is permitted at 1.0 mm leakage test as compared to 0.5 mm leakage test.
Hint: Evaporation increases under warm conditions. It increases even more when winter fuel is used under warm conditions. Fuel evaporation can be reduced by allowing the fuel to cool. Speed cooling by spraying the fuel tank with cold water.
Other information
- For more information on tank system diagnostics: Leak diagnostics Leak Diagnostics
1. Canister purge (CP) valve
2. EVAP canister
3. EVAP canister shut-off valve
4. Fuel tank pressure sensor
5. Air cleaner (ACL)
Location Of Components:
Continue - Starting the quick test
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Starting the quick test
Note! Do not start the test if engine temperature is less than 30° C.
- Engine idling
- Start the quick test.
Hint: If the EVAP canister is overfull, the engine may start to run unevenly and possibly even stall. If this happens, restart the engine and the quick test. Let the engine idle until the status changes from inhibited to running. Then increase the engine speed (RPM) to between 1500-2000 rpm. Maintain this engine speed (RPM) until the status changes to finished.
Information
In the event of tank system leakage, only one diagnostic trouble code will be generated. Thus, only status box DTC1 will contain information. The other status box will remain empty.
If there is a smaller leak that is not large enough for a diagnostic trouble code (DTC) to be stored, 2 diagnostic trouble codes (DTCs) and the test values will be displayed. These test values must be checked to ensure that they correspond with the values in the table. See Reading off the test results / the fuel tank values Reading Off the Test Results / the Fuel Tank Values.
Other parameters:
- EVAP canister shut-off valve. Closes when it is active, ON (red line).
- Fuel tank pressure (yellow line).
- Canister purge (CP) valve (green line).
Hint: When the curves go outside the measurement range, press "AUTORANGE" so that they are visible within the measurement range again.
The quick test process
When the quick test is complete, the result is displayed in status window DTC1 and where applicable DTC2.
If a fault was detected during the test, a diagnostic trouble code (DTC) and a test value will be displayed. Fault-tracing must then be carried out by selecting this test.
If no faults were found during the test, diagnostic trouble codes (DTCs) will be displayed in both the status windows instead. The test value must then be compared with the quantity of fuel in the fuel tank to determine whether there is a small leak that the quick test was unable to detect. (See the information above).
The following alternatives are available:
1. When the leak diagnostic is complete and the test has ended without any faults being detected.
2. When the test has detected a fault in the EVAP canister shut-off valve or in the canister purge (CP) valve.
3. When the test has detected a large leak.
4. When the test has detected a fault in the canister purge (CP) valve.
5. When the test has detected a small leak.
6. The test does not start or is prematurely interrupted.
Select an alternative.
1 - Fault Found
2 - EVAP canister shut-off valve
3 - Rough leak
4 - Canister purge (CP) valve
5 - Small leak
6 - Checking the cause of the problem with quick test
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Checking the cause of the problem with quick test
Hint: If the quick test does not start or is prematurely interrupted, it could be because:
- engine temperature is below 30 °C
- there is too much fuel in the tank
- there is high fuel evaporation
- there is a blockage between the tank pressure sensor and the tank
The method below is used to determine if the problem with the quick test is caused by high evaporation or a blockage between the tank pressure sensor and the tank. This is done by running the test with the tank cap removed. Normally, a major leak is detected if the cap is off.
Note! If the canister is filled with fuel vapor, the test is interrupted. The canister fills with fuel vapor more quickly if the canister purge valve is regulating and the tank cap is removed. Therefore, start the quick test immediately after engine start and do not allow the engine to idle more than necessary.
- Remove the tank cap.
- Engine idling
- Start the quick test with the tank cap removed.
Especially check tank pressure (yellow line) during the test for major leaks.
If the quick test is not interrupted when the tank cap is removed and a major leak is detected after quick test completion, fuel evaporation is too high. Fuel evaporation can be reduced by allowing the fuel to cool. Speed cooling by spraying the fuel tank with cold water.
If the quick test is interrupted or a small leak is detected when the tank cap is removed and tank pressure (yellow line) drops more quickly than normal during the test, there may be blockage in a hose or hose connection between the tank and tank pressure sensor. This can be fault traced by detaching the hoses to EVAP system components (one at a time) and performing a quick test for each. If a major leak is detected after the quick test when the hose has been disconnected, the fault is against the direction of airflow (calculated from the disconnected hose).
Hint: Airflow direction during the quick test can be calculated from the fuel tank: fuel tank, canister, canister purge valve, intake pipe. The tank pressure sensor measures the pressure in the hose between the fuel tank and the canister.
If, for example, the hose to the canister is detached from the fuel tank and a major leak is detected, there is a blockage in the tank hose connection.
Remedy as necessary.
Restore all components and then perform a quick test of the tank system before delivering the vehicle to the customer.
Select an alternative to continue:
1. Continue fault tracing for the diagnostic trouble code.
2. Exit.
1 - Starting the quick test
2 - DONE
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Checking blockage between tank pressure sensor and tank
Hint: If a small leak is detected after a quick test of the tank system, in may be due to blockage between the tank pressure sensor and the tank.
The method below is used to determine if the small leak detected after the quick test is caused by blockage between the tank pressure sensor and tank. This is done by running the test with the tank cap removed. Normally, a major leak is detected if the cap is off. If a small leak is detected when the tank cap is off, there is a blockage between the tank pressure sensor and the tank.
Note! If the canister is filled with fuel vapor, the test is interrupted. The canister fills with fuel vapor more quickly if the canister purge valve is regulating and the tank cap is removed. Therefore, start the quick test immediately after engine start and do not allow the engine to idle more than necessary.
- Remove the tank cap.
- Engine idling
- Start the quick test with the tank cap removed.
Especially check tank pressure (yellow line) during the test for major leaks.
If a major leak is detected when the tank cap is off, the cause of the fault is likely leakage. Continue fault tracing as described for a small leak.
If the test is interrupted or a small leak is detected when the tank cap is removed and tank pressure (yellow line) drops more quickly than normal during the test, there may be blockage in a hose or hose connection between the tank and tank pressure sensor. This can be fault traced by detaching the hoses to EVAP system components (one at a time) and performing a quick test for each. If a major leak is detected after the quick test when the hose has been disconnected, the fault is against the direction of airflow (calculated from the disconnected hose).
Hint: Airflow direction during the quick test can be calculated from the fuel tank: fuel tank, canister, canister purge valve, intake pipe. The tank pressure sensor measures the pressure in the hose between the fuel tank and the canister.
If, for example, the hose to the canister is detached from the fuel tank and a major leak is detected, there is a blockage in the tank hose connection.
Remedy as necessary.
Restore all components and then perform a quick test of the tank system before delivering the vehicle to the customer.
Select an alternative to continue:
1. Continue fault tracing for small leak.
2. Exit.
1 - Small leak
2 - DONE
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Rough leak
Rough leak
Checking the vacuum downstream of the canister purge (CP) valve
Note! As the illustrations in this service information are used for different model years and / or models, some variation may occur. However, the essential information is always correct.Some of the illustrations only apply to C70/S70/V70. However they are also a guide for working on the S80.
- Start the engine and let it idle.
- Disconnect the hose between the canister purge (CP) valve and the EVAP canister from the canister purge (CP) valve.
- Read off the canister purge (CP) valve. This is to check whether the valve is activated.
Check that there is a vacuum in the canister purge (CP) valve when the valve is activated.
Is there a vacuum?
Yes - Checking the vacuum at the EVAP canister
No - Checking the canister purge (CP) valve vacuum
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Checking the vacuum at the EVAP canister
- Ignition off.
- Reconnect the hose on the canister purge (CP) valve.
- Disconnect the hose to the canister purge (CP) valve from the EVAP canister.
- Start the engine and let it idle.
- Read off the canister purge (CP) valve value. This is to determine whether the valve is activated or not.
Check that there is a vacuum in the hose when the canister purge (CP) valve is activated.
Is there a vacuum?
Yes - Checking the EVAP canister
No - Checking the hose
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