B - Pressure Test in the Fuel Supply Line
- Connect the measuring setup as if measuring the delivery quantity.
- Vehicle Diagnostic Tester still connected.
-- Switch on the :VAS6551 -1- by pressing the On/Off button.
-- Open the shut-off valve -A-.
- The lever points in the direction of flow.
Risk of fuel leak.
- The shut-off valves -B and C- must be closed.
- The levers face perpendicular to the flow direction.
-- Press Start on the display of the Vehicle Diagnostic Tester: The fuel pump starts.
-- After 15 seconds, press the Stop button.
-- Read the fuel pressure in the :VAS6551 .
- Specified value: minimum 6 bar (87 psi).
If Specified Value Is Obtained, Although the Fuel Delivery Unit Is Not OK
- The fuel filter is clogged or the fuel supply line is kinked
If Specification Is Not Attained
- The fuel pump or fuel pressure regulator in the fuel tank is faulty.
To also locate malfunctions in the fuel return line or the high pressure pump overflow valve, the "Entire system pressure test" must be performed as described in the following.
Before replacing the measuring system, reduce the fuel pressure by opening the shut-off valves -B and C- and allowing the fuel to drain into the measuring container.
-- Disassemble the :VAS6551/6 and remove it with the measuring container.