Fuel Pressure Test

Special tools and workshop equipment required

Multimeter.
fuel line adapter set V.A.G. 1318/17A. These tools may be substituted with an equivalent aftermarket tool and are also available for rental or purchase through Volkswagen.
In line Fuel pressure gauge with shutoff valve. (high pressure gauge).

Test conditions

Battery voltage 12.5 V
Function and voltage supply for the Fuel Pump is OK. If not, perform the Fuel Pump electrical test above.
Fuel tank at least ¹ /₄ filled.
Ignition switched OFF.

Test procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK

WARNING:

Fuel system is under pressure! Before opening the system, place rags around the connection area, wear safety glasses. Then release the pressure by carefully loosening the connection. Refer to the Repair Information.

Start diagnosis

-- Disconnect fuel supply line -3- at the supply location and catch any fuel coming out with a shop towel.

Fig 1: Identifying Breather Line, Vacuum Line & Fuel Supply Line

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

NOTE:

Pull circlip upward to unlock fuel line

-- Install a fuel pressure gauge with appropriate adapters.

-- Open shut off valve on fuel gauge.

-- Switch ignition ON and OFF in 5 second intervals repeatedly until fuel pressure gauge stops increasing pressure.

-- Switch ignition OFF.

-- Read fuel pressure on the gauge.

Specified value: 3.5 to 6 bar

If specification is exceeded:

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

If no malfunction in fuel return line is found:

-- Pressure relief valve in fuel filter is malfunctioning.

-- Replace the fuel filter. Refer to the Repair Information.

If reading was below the specification:

-- Check fuel pressure at the fuel filter between fuel pump and fuel filter using appropriate adapters

-- Open shut off valve on gauge and start the engine. Allow to idle.

-- Slowly close the pressure gauge shut off and note the fuel pressure.

NOTE:

When 6 bar is reached: Open shut off tap immediately!

Pressure should increase to 6 bar.

If pressure has increased during test:

-- Fuel pump is OK. Pressure relief valve in fuel filter is malfunctioning.

-- Replace the fuel filter. Refer to the Repair Information.

If pressure did not increase:

-- Fuel pump is faulty

-- Replace the fuel pump. Refer to the Repair Information.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .