Part 2
Leak diagnostic (Continued)
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 run at idle speed.
- 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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Checking the canister purge (CP) valve vacuum
- Connect the hose between the canister purge (CP) valve and the EVAP canister to the canister purge (CP) valve.
- Start the engine and let it run at idle speed.
- Disconnect the hose between the canister purge (CP) valve and the intake manifold from the canister purge (CP) valve.
Check that there is a vacuum in the hose.
Remedy as necessary.
Was a fault detected?
Yes - Starting the test of the fuel tank system
No - Replacing the component
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Replacing the component
Try a new canister purge (CP) valve .
Continue - Starting the test of the fuel tank system
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Checking the EVAP canister
Check that all EVAP canister inlets and outlets are not sealed.
Hint: Connect a vacuum pump to the EVAP canister terminals, one at a time. Check that it is not possible to pump negative pressure.
Other information:
- To access / replace the EVAP canister, see Replacing the carbon filter container Service and Repair.
Was a fault detected?
Yes - Starting the test of the fuel tank system
No - Checking the hose between the fuel tank and the EVAP canister
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Checking the hose
Check if the hose between the canister purge (CP) valve and the EVAP canister is blocked or trapped.
Continue - Starting the test of the fuel tank system
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Checking the hose between the fuel tank and the EVAP canister
Check that the hose between the fuel tank and EVAP canister is airtight and is not trapped.
Remedy as necessary.
Was a fault detected?
Yes - Starting the test of the fuel tank system
No - Test pressurization of the fuel tank system
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Test pressurization of the fuel tank system
- Max 50 liters of fuel in the fuel tank.
- Ignition off.
- Connect the hose from the fuel tank to the EVAP canister.
- Clamp the hose between the EVAP canister shut-off valve and the EVAP canister with a hose clip to seal it.
- Carefully disconnect the EVAP canister hose from the canister purge (CP) valve.
Connect manometer999 5646 Pressure gauge 999 5646 Pressure Gauge to the hose and the pressure regulator999 5544 REGULATOR 999 5544 Regulator to the manometer.
Set the pressure to 7 kPa (read off on manometer999 5646 Pressure gauge 999 5646 Pressure Gauge ).
The cock must be at right angles to the hoses.
Warning! Max 10 kPa.
Let the pressure build up for 5 minutes.
Close the cock (the pressure may now drop by 1-2kPa before it stabilizes). Read off the pressure.
Turn the cock towards the EVAP canister hose.
Wait for 10 minutes.
Warning! Never leave the car unattended with its fuel tank system pressurized.
The pressure must be stable (it may rise a little due to fuel evaporation).
Is the pressure stable?
Yes - Checking the fuel tank pressure sensor
No - Checking the fuel tank system
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Checking the fuel tank pressure sensor
- Disconnect tool999 5646 Pressure gauge 999 5646 Pressure Gauge.
- Connect the EVAP canister hose.
- Remove the hose clamp from the hose between the canister purge (CP) valve and the intake manifold.
- Start the engine and let it run at idle speed.
- Read off the value for the fuel tank pressure and the canister purge (CP) valve.
When the canister purge (CP) valve opens, the pressure in the fuel tank must drop.
Has the pressure in the fuel tank dropped?
Yes - Checking the hose to the EVAP canister shut-off valve
No - Checking the fuel tank pressure sensor hose
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Checking the hose to the EVAP canister shut-off valve
Check the hose to the EVAP canister shut-off valve. Check the seal. Check the terminals.
Remedy as necessary.
Was a fault detected?
Yes - Starting the test of the fuel tank system
No - Replacing the component
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Checking the fuel tank pressure sensor hose
- Ignition off.
- Remove the fuel tank pressure sensor.
- Remove the hose with the Y-nipple.
Check that the nipple and hoses are not blocked.
Remedy as necessary.
Other information:
- To access / replace the fuel tank pressure sensor see Replacing fuel tank pressure sensor Service and Repair.
Was a fault detected?
Yes - Starting the test of the fuel tank system
No - Replacing the component
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Replacing the component
Try a new fuel tank pressure sensor according to Replacing fuel tank pressure sensor Service and Repair..
Continue - Starting the test of the fuel tank system
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Replacing the component
Try a new EVAP canister shut-off valve according to Replacing the shut-off valve for the carbon filter container Service and Repair.
Continue - Starting the test of the fuel tank system
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Checking the fuel tank system
- Ignition off.
- Carefully pressurize the fuel tank system to 7 kPa. The cock must be at right angles to the hoses.
Note! Max 10 kPa.
Check the fuel tank system by spraying soapy water from the EVAP canister to the canister purge (CP) valve. Also spray the line between the fuel tank and the EVAP canister shut-off valve. Also check the filler pipe and the fuel tank filler cap.
It may be necessary to lower the fuel tank in order to fault-trace hoses and connectors on top of the fuel tank.
Remedy the leakage.
Continue -Starting the test of the fuel tank system
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Small leak
Test pressurization of the fuel tank system
- Max 50 liters of fuel in the fuel tank.
- Ignition off.
- Clamp the hose between the EVAP canister shut-off valve and the EVAP canister with a hose clip to seal it.
- Carefully disconnect the EVAP canister hose from the canister purge (CP) valve.
Connect manometer999 5646 Pressure gauge 999 5646 Pressure Gauge to the hose and the pressure regulator999 5544 REGULATOR 999 5544 Regulator to the manometer.
Set the pressure to 7 kPa (read off on the manometer999 5646 Pressure gauge 999 5646 Pressure Gauge.
The cock must be at right angles to the hoses.
Warning! Max 10 kPa.
Let the pressure build up for 5 minutes.
Close the cock (the pressure may now drop by 1-2 kPa before it stabilizes). Read off the pressure.
Turn the cock towards the EVAP canister hose.
Wait for 10 minutes.
Warning! Never leave the car unattended with its system pressurized.
The pressure must be stable (it may rise a little due to fuel evaporation).
Is the pressure stable?
Yes - Checking the hose to the EVAP canister shut-off valve
No - Checking the fuel tank system
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Checking the hose to the EVAP canister shut-off valve
Check the hose to the EVAP canister shut-off valve. Check the seal. Check the terminals.
Remedy as necessary.
Is the hose OK?
Yes - Replacing the component
No - Starting the test of the fuel tank system
------------------------
Replacing the component
Try a new EVAP canister shut-off valve .
Continue - Starting the test of the fuel tank system
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Checking the fuel tank system
- Ignition off.
- Carefully pressurize the fuel tank system to 7 kPa.
Turn the EVAP canister shut-off valve so that it is at a right angle to the hoses.
Warning! Max 10 kPa
Check the fuel tank system by spraying it with soapy water from the EVAP canister to the canister purge (CP) valve. Also spray the line with the pressure regulator and roll-over valve to the fuel tank. Also check the filler pipe and the fuel tank filler cap.
It may be necessary to lower the fuel tank in order to fault-trace hoses and connectors on top of the fuel tank.
Warning! Never leave the car unattended with its system pressurized.
Continue - Starting the test of the fuel tank system
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Verification information
Hint: After carrying out the check and the repair, check that the fault has been remedied.
Continue - Starting the test of the fuel tank system
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Leakage
Checking the vacuum downstream of the canister purge (CP) valve
- Disconnect the hose between the canister purge (CP) valve and the EVAP canister from the canister purge (CP) valve.
- Start the engine and let it run at idle speed
Read off the canister purge (CP) valve pulse signal.
There should not be a vacuum in the canister purge (CP) valve when the pulse signal is 0%.
Other information
- To access / replace the canister purge (CP) valve, see the relevant service procedure.
Is the canister purge (CP) valve OK?
Yes - Checking the canister purge (CP) valve
No - Starting the test of the fuel tank system
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Checking the canister purge (CP) valve
Check the canister purge (CP) valve connector for dirt, damage and deposits.
Activate the canister purge (CP) valve to ensure that no function faults occur.
Check that the canister purge (CP) valve does not jam or stop functioning after it has been activated.
Continue - Starting the test of the fuel tank system
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Flow fault
Checking the fuel tank pressure sensor
- Open the fuel tank filler cap.
- Start the engine and let it run at idle speed.
Read off the fuel tank pressure.
Hint: The fuel tank pressure must be higher than -10 hPa. The normal value is close to 0 hPa.
Is the fuel tank pressure OK?
Yes - Checking the canister purge (CP) valve
No - Starting the test of the fuel tank system
------------------------
Checking the canister purge (CP) valve
- Disconnect the hose between the canister purge (CP) valve and the EVAP canister from the canister purge (CP) valve.
- Start the engine and let it run at idle speed.
Read off the canister purge (CP) valve pulse signal.
There should not be a vacuum in the canister purge (CP) valve when the pulse signal is 0%.
Other information
- To access / replace the canister purge (CP) valve, see the relevant service procedure.
Is the value correct?
Yes - Checking hoses
No - Starting the test of the fuel tank system
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Checking hoses
Check that the EVAP canister shut-off valve is not sealed.
Check that the EVAP canister shut-off valve filter is not sealed.
Check the hoses between the EVAP canister and the EVAP canister shut-off valve and between the EVAP canister shut-off valve and its filter for blockages and crimping.
Check the EVAP canister shut-off valve terminal in the EVAP canister for blockage.
Remedy as necessary.
- To access / replace the EVAP canister shut-off valve see Replacing the shut-off valve for the carbon filter container Service and Repair.
Continue - Starting the test of the fuel tank system
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