Fuel Pressure, Checking

WARNING: This page is about a different car, the 2009 Volkswagen GTI and 2008 Volkswagen GTI. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

The output Diagnostic Test Mode (DTM) checks the fuel pressure.

WARNING:

The fuel supply line is under pressure. Always wear protective eyewear and protective clothing to prevent injuries and fuel from coming in contact with your skin. Wrap a cloth around the connection before removing a fuel hose. Remove the hose connection carefully to release the pressure.

-- Disconnect the supply line (metal coupling) -arrow- and collect any leaking fuel with a cloth.

Fig 1: Identifying Supply Line

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NOTE:

Press in the securing ring to disengage the fuel line.

-- Connect the pressure tester -VAS 6550- to the fuel supply line using the hoses -VAS 6550/1- and -VAS 6550/2-.

Fig 2: Identifying Pressure Tester VAS 6550 To Fuel Supply Line And Adapters VAS 6550/1 & VAS 6550/2

Courtesy of VOLKSWAGEN UNITED STATES, INC.

-- Make sure the drain is closed and the shut-off levers are open.

-- Activate the fuel pump with output DTM to build fuel pressure.

-- Check the fuel pressure on the pressure tester.

Specified value: 4.0 to 7.0 bar

If the fuel pressure is OK, check the residual pressure. Refer to RESIDUAL PRESSURE, CHECKING .

If the Specification is Exceeded

-- Check the return line between the fuel filter and the fuel pump for kinks or blockages.

If no malfunction can be found:

-- The pressure relief valve in the fuel filter is malfunctioning, replace the fuel filter.

If the Specification is Not Obtained

-- Check the fuel pressure before the fuel filter as follows:

-- Disconnect the fuel supply line -arrow- from the fuel filter.

Fig 3: Identifying Fuel Supply Line At Fuel Filter

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-- Connect the pressure tester -VAS 6550- between the fuel filter and fuel supply line using hoses -VAS 6550/1- and -VAS 6550/2-.

Fig 4: Identifying Pressure Tester VAS 6550 And Hoses VAS 6550/1 & VAS 6550/2

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-- Make sure the drain is closed and the shut-off levers are open.

Fig 5: Identifying Shutoff Levers

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-- Turn on the ignition and actuate the fuel pump using the output DTM.

-- Close the shut-off lever -A- while the fuel pump is running. Pressure must increase to a minimum of 7.0 bar. If 7.0 bar is reached, open the shut-off lever again immediately.

If the pressure has increased:

-- Replace the fuel filter, the fuel pump is OK but the pressure relief valve in the fuel filter is faulty.

If the pressure does not increase:

-- Replace the fuel delivery unit, the fuel pump is faulty. Refer to FUEL DELIVERY UNIT .