Fuel Pressure Test

Ensure engine is off. Ensure battery voltage is at least 12 volts. Release fuel pressure, see FUEL SYSTEM PRESSURE RELEASE .
Place a clean shop rag around fuel line test fitting and slowly loosen fitting. Connect Fuel Gauge (VAG 1318) with Hose (VAG 1318/1) or equivalent to test connection on fuel rail. See Fig 1 . Fuel gauge valve must be closed, handle 90 degrees to direction of flow (arrow).

Fig 1: Checking Fuel Pressure (2.8L VR6)
Courtesy of VOLKSWAGEN UNITED STATES, INC.
Install fuse or fuel pump relay. Start and run engine at idle speed. Compare fuel pressure on gauge to fuel pressure specifications. See FUEL PRESSURE SPECIFICATIONS (2.8L VR6) table.
Disconnect vacuum hose from fuel pressure regulator. See Fig 1 . Fuel pressure must rise as specified. See FUEL PRESSURE SPECIFICATIONS (2.8L VR6) table. Turn ignition off.
Check for leaks and residual pressure by watching pressure drop on gauge. After 10 minutes residual pressure must be as specified. See FUEL PRESSURE SPECIFICATIONS (2.8L VR6) table.
If pressure drops below specification, start and run engine at idle speed. After the pressure has built up, turn ignition off, and at the same time clamp-off return line (line with blue arrow) on fuel rail. Again watch fuel pressure drop.
If the pressure does not drop, replace fuel pressure regulator. If the pressure drops again, check fuel pump check valve. See FUEL SYSTEM in appropriate 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⁾

43 (3)

Residual Pressure⁽³⁾

29 (2)

⁽¹⁾	With fuel pressure regulator vacuum hose connected.

⁽²⁾	With fuel pressure regulator vacuum hose disconnected.

⁽³⁾	After 10 minutes.