If the Pressure Drops:

-- Check all of the fuel lines for leaks and damage.

If No Faults Can Be Found:

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

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

-- Activate the fuel pump using the output diagnostic test mode to build the fuel pressure.

-- Close the shut-off valve -B- on the pressure gauge immediately after the pressure has been reached. The lever is perpendicular to the flow direction.

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

Proceed as follows to check residual pressure on the fuel delivery unit. Refer to Residual Pressure in Fuel Delivery Unit, Checking: .