Residual Pressure, Checking

WARNING: This page is about a different car, the 2014 Volkswagen Touareg, 2013 Volkswagen Touareg, 2012 Volkswagen Touareg, and 2011 Volkswagen Touareg. However, it is still accessible from the selected car via links, so may be relevant.

Test Conditions

The : VAS6550 must be connected. Refer to FUEL PRESSURE, CHECKING .

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
Fuel pressure approximately 5 bar (72.5 psi)

Test Sequence

-- Observe the pressure drop on the pressure gauge. After 10 minutes the pressure must not drop below a 4.3 bar (62.3 psi) decrease.

If the pressure drops below 4.3 bar (62.3 psi) :

-- Switch the ignition on.

-- On the OBD screen, press one button after the other: 01 - engine electronics and output diagnostic test mode .

-- Push the arrow button → on the display to the fuel pump electronics output diagnostic test mode .

The fuel pump must now accelerate slowly up to the maximum RPM.

-- Read the pressure on the : VAS6550 .

Specified value: 5.0 to 7.0 bar (72.51 to 101.52 psi)

-- Switch on the ignition and immediately close shut-off valve "B" of the pressure tester. shut-off valve "B" points perpendicular to the direction of flow.

-- Observe the decrease in pressure on the pressure gauge. After 10 minutes the pressure must not drop below a 4.3 bar (62.36 psi) decrease.

If the Pressure Stops Decreasing Now (Leak on the Engine Side):

Check for the leak on the engine-side, proceed as follows. Refer to RESIDUAL PRESSURE, CHECKING .

If the Pressure Drops Again (Leak on Fuel Tank Side):

Check for the leak on the fuel tank side. Proceed as follows:

-- Check the fuel tank connections for leaks.

If No Error Can Be Found:

-- Check the fuel line to the sensor flange -item 14- OVERVIEW - FUEL DELIVERY UNIT, FUEL LEVEL SENSOR AND SUCTION JET PUMPS List Item:Flange for leaks.

-- Check all additional fuel lines in fuel tank for leaks.

If No Faults Are Found on Fuel Line:

-- Replace the fuel delivery unit. Refer to FUEL DELIVERY UNIT AND Fuel Level Sensor -G-, REMOVING AND INSTALLING .

NOTE:

If the : VAS6550 is to be removed, open shut-off valve "C" and reduce the residual pressure. For this purpose, hold the hose of shut-off valve "C" in a measuring container.

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

If the Pressure No Longer Decreases (Leak on the Engine Side):

NOTE:

Check for the leak on the engine-side. To do so repeat the pressure test. Close the shut-off valve -A- this time to determine if there actually is a leak on the engine side.

-- If there is a leak on the engine-side, check the fuel pipes and high pressure pump >>externally<< for leaks.

If no malfunction is found, check the fuel injectors for leaks:

-- Remove the spark plugs. Open the shut-off valves -A and B-. Activate the fuel pump with the output diagnostic test mode.

-- Check through the spark plug hole if fuel is collecting on the piston crown due to a leaking fuel injector.