Fuel Pressure, Checking

WARNING: This page is about a different car, the 2023 Volkswagen Atlas. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Trim Removal Wedge:3409
Pressure Tester Kit:VAS6550
Pressure Tester Kit - Hose 1:VAS6550/1
Pressure Tester Kit - Hose 2:VAS6550/2
Pressure Tester Kit - Adapter Set - Hose 3:VAS6550/3-3
Pressure Tester Kit - Adapter Set - Hose 4:VAS6550/3-4
Vehicle Diagnostic Tester

Conditions:

Voltage supply OK. Refer to FUEL PUMPS, CHECKING FUNCTION AND POWER SUPPLY .

CAUTION:

The fuel system is under pressure.

Risk of injury from fuel spraying out.

- Wear protective eyewear.

- Wear safety gloves.

- Reduce the pressure: place clean cloths around the connection point and carefully open the connection point.

-- Remove the supply line -1-. Disconnect the connector couplings. Refer to CONNECTOR COUPLINGS, DISCONNECTING .

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Collect leaking fuel with a cleaning cloth.

-- Connect the :VAS6550/1 to the connection -A- on the :VAS6550 .

Fig 1: Identifying Pressure Tester Kit - Hose 1 VAS 6550/1

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Connect the :VAS6550/1 to the fuel supply line -1- to the engine.

-- Connect the :VAS6550/2 to the connection -B- on the :VAS6550 .

-- Connect the fuel line to the fuel tank with the :VAS6550 via the :VAS6550/2 .

-- Pull on the connector couplings to check them for secure fit.

-- Make sure that the drain valve -C- on the :VAS6550 -1- is closed.

Fig 2: Identifying Shut-Off Valves A And B On Pressure Tester Kit

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- The shut-off valves -A and B- on the :VAS6550 -1- are opened.

-- Connect the Vehicle Diagnostic Tester to the vehicle.

-- Select the fuel pump output diagnostic test mode in OBD.

NOTE:

The fuel pump is now activated to build up the fuel pressure.

If the output diagnostic test mode was performed several times in succession, the engine may need to be started briefly before repeating the output diagnostic test mode.

-- Read the fuel pressure on the pressure gauge.

Specified value: 4 to 7 bar (58.01 to 101.52 psi).

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

If the Specified Value is Exceeded:

-- The pressure relief valve in the fuel delivery unit is faulty.

-- Replace the fuel delivery unit. Refer to FUEL DELIVERY UNIT/FUEL LEVEL SENSOR, REMOVING AND INSTALLING .

If the Specified Value Is Not Obtained:

Proceed as follows to check the fuel pressure at the fuel delivery unit:

-- Remove the installation opening cover. Refer to FUEL DELIVERY UNIT COVER, REMOVING AND INSTALLING .

-- Remove the Fuel Pump Control Module -J538- with the connected wiring harness. Refer to Fuel Pump Control Module -J538-, REMOVING AND INSTALLING .

-- Remove the Fuel Pump Control Module -J538- toward the inside between the fuel tank and the floor panel.

-- Move the Fuel Pump Control Module -J538- together with the wiring harness to the side.

CAUTION:

The fuel system is under pressure.

Risk of injury from fuel spraying out.

- Wear protective eyewear.

- Wear safety gloves.

- Reduce the pressure: place clean cloths around the connection point and carefully open the connection point.

-- Remove the fuel lines -1- from the flange. Disconnect the connector couplings. Refer to CONNECTOR COUPLINGS, DISCONNECTING .

Fig 3: Fuel Lines to the Fuel Delivery Unit

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Connect the :VAS6550 to the fuel delivery unit -1- using the :VAS6550/3-4 .

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Connect the :VAS6550/3-3 between the :VAS6550 and the fuel supply line -2-.

-- Pull on the connector couplings to check them for secure fit.

-- Make sure that the drain valve -C- on the :VAS6550 -1- is closed.

Fig 4: Identifying Shut-Off Valves A And B On Pressure Tester Kit

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- The shut-off valves -A and B- on the :VAS6550 -1- are opened.

-- Repeat the output diagnostic test mode to build up the fuel pressure again.

If the Specified Value Is Obtained:

-- Check the fuel lines for possible restrictions (kinks) or blockages.

-- Check the fuel line for leaks and damage.

If the Specified Value Is Not Obtained:

Fig 5: Identifying Delivery Unit Fuel Hoses

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Remove the fuel delivery unit and inspect it for debris. Refer to FUEL DELIVERY UNIT/FUEL LEVEL SENSOR, REMOVING AND INSTALLING .

-- Make sure all hoses -arrows- are connected.

-- Check the fuel lines for possible restrictions (kinks) or blockages.

-- Check if the vacuum lines are connected.

-- Check the fuel lines for leaks and damage.

If No Error Can Be Found:

-- If the fuel pump is faulty, replace the fuel delivery unit. Refer to FUEL DELIVERY UNIT/FUEL LEVEL SENSOR, REMOVING AND INSTALLING .