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Fuel Pressure Test (2.8L VR6, Engine Code AES)

  1. Ensure ignition is off. Ensure battery voltage is at least 12 volts. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE (2.8L VR6, ENGINE CODE AES)  .
  2. Remove plug (1) on fuel pressure regulator bracket. See Fig 1 . Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply test connection. Ensure shut-off valve is in closed position (90 degrees to direction of fuel flow). Fuel pressure gauge shut-off valve must remain in closed position.
    Fig 1: Locating Fuel Supply Test Connection & Connecting Fuel Pressure Gauge (2.8L VR6, AES)
    G00083328Courtesy of VOLKSWAGEN UNITED STATES, INC.
  3. Start engine and idle. Fuel pressure should be within specification. See FUEL PRESSURE SPECIFICATIONS (2.8L VR6)  table.
  4. Continue to idle engine. Disconnect vacuum line from fuel pressure regulator. See Fig 2 . For specification, see FUEL PRESSURE SPECIFICATIONS (2.8L VR6)  table.
    Fig 2: Disconnecting Fuel Pressure Regulator Vacuum Hose (2.8L VR6, AES)
    G00083329Courtesy of VOLKSWAGEN UNITED STATES, INC.
  5. If fuel pressure is not as specified, check fuel pump volume. See FUEL PUMP VOLUME CHECK  . If fuel pressure is as specified, go to next step.
  6. Perform fuel system residual pressure test. Reinstall vacuum hose on fuel pressure regulator and continue to run engine at idle. Turn engine off.
  7. Check residual fuel pressure after 10 minutes. See FUEL PRESSURE SPECIFICATIONS (2.8L VR6)  table. If residual fuel pressure drops below specification, check for fuel leaks and repair as necessary. Recheck residual fuel pressure. If residual fuel pressure is still not as specified, start and idle engine. After fuel pressure build up, turn off ignition. At the same time clamp off fuel return line (blue markings) on fuel pressure regulator bracket.
  8. Observe residual fuel pressure drop again. If fuel pressure does NOT drop, check for leaking fuel injectors or fuel pressure regulator. If fuel pressure drops, check for leaking fuel lines between fuel rail and fuel tank. Repair as necessary. If fuel lines are okay, test for faulty fuel pump check valve. See FUEL PUMP CHECK VALVE  .
NOTE: To test for leaking fuel injectors, see FUEL INJECTOR TESTS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING article.
FUEL PRESSURE SPECIFICATIONS (2.8L VR6)

Function psi (bar)
System Pressure
With Engine Idling (1) 36 (2.5)
With Engine Idling (2) 44 (3.0)
Residual Pressure (3) 29 (2.0)
(1) With fuel pressure regulator vacuum hose connected.
(2) With fuel pressure regulator vacuum hose disconnected.
(3) Minimum pressure 10 minutes after engine shut down.
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