Checking fuel pressure

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Special tools, testers and auxiliary items required

Fuel pressure gauge

CAUTION: Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before loosening hose connections, place rags around the connection point. Then release pressure by carefully pulling on hose.

Fig 1: Identifying Vacuum Hose To Throttle Valve Control Module, Fuel Return Hose & Fuel Supply Hose

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Remove the fuel supply line - 3 - and catch leaking fuel using a rag.

Fig 2: Connecting VAG 1318 Components To Fuel Supply Line

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Install a Fuel pressure gauge and hold into a measuring container.
Open the shut-off valve of the Fuel pressure gauge.
Switch the ignition on and off until the fuel pressure on no longer rises.
Check the indicated fuel pressure on the Fuel pressure gauge.

Specified value: 2.5 bar minimum.

If specified value is obtained:

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

If no malfunction is found in the return line between the fuel filter and the fuel pump:

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

If specified value is not obtained:

Check the fuel pressure in front of the fuel filter.

Fig 3: High Pressure Fuel Gauge Connected Between The Fuel Filter And The Fuel Supply Line

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Connect a High pressure fuel gauge between the fuel filter and the fuel supply line.
Open the shut-off valve of the Fuel pressure gauge.
Start the engine and let it run at idle.

CAUTION: Shut-off valve must only be closed slowly. At a fuel pressure of 8 bar, shut-off valve must be opened again immediately to prevent damage to pressure measuring device.

Fig 4: Closing The Shut-Off Valve Of The High Pressure Fuel Gauge

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Slowly close the shut-off valve of the Fuel pressure gauge. Pressure must increase to min. 6.0 bar. If 6 bar is reached, open shut-off valve again immediately!

If the fuel pressure increases:

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

If the fuel pressure does not increase:

Replace the fuel pump. Refer to 20 - FUEL SUPPLY .

Final procedures

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

Check the DTC memory.
If necessary, erase the DTC memory.
If the DTC memory was erased, generate readiness code.

End diagnosis