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Fuel System Pressure

  1. Ensure fuel pump relay is okay. Ensure correct fuel filter is installed. Ensure battery voltage is at least 12 volts. Release fuel pressure.
  2. Connect Pressure Gauge (VAG 1318) between fuel supply and fuel return lines in engine compartment. See Fig 3 . Disconnect and plug vacuum line from fuel pressure regulator. Start engine, and let idle. Fuel pressure should be within specification. See appropriate FUEL PRESSURE SPECIFICATIONS table.
    FUEL PUMP PERFORMANCE (TT - 1.8L)

    Application Specification
    System Pressure (1)
    With Engine Idling (2) 44 psi (3.0 bar)
    With Engine Idling (3) 36 psi (2.5 bar)
    Residual Pressure (4) 22-36 psi (1.5 bar)
    Minimum Volume In 30 Sec. (5)
    Engine Code AMU 5.6-6.2 ozs. (165-183 ml.)
    Engine Codes ATC & AWP 4.5-5.3 ozs. (133-157 ml.)
    (1) Battery voltage must be 11 volts or more when checking system pressure.
    (2) With fuel pressure regulator vacuum hose disconnected.
    (3) With fuel pressure regulator vacuum hose connected.
    (4) After 10 minutes.
    (5) Volume is dependent upon battery voltage and should be checked with battery fully charged. See Fig 1 .
    Fig 1: Measuring Fuel Pump Volume (1.8L & 3.0L V6)
    G00266864Courtesy of AUDI OF AMERICA, INC.
    FUEL PUMP PERFORMANCE (3.0L)

    Application Specification
    System Pressure (1)
    With Engine Idling (2) 46-55 psi (3.2-3.8 bar)
    With Engine Idling (3) 55-61 psi (3.8-4.2 bar)
    Residual Pressure
    Cold Engine (4) 32 psi (2.2 bar)
    Warm Engine (4) 44 psi (3.0 bar)
    Min. Vol. In 30 Sec. (5) 3.0-4.2 ozs. (90-125 ml.)
    (1) Battery voltage must be 11 volts or more when checking system pressure.
    (2) With fuel pressure regulator vacuum hose connected.
    (3) With fuel pressure regulator vacuum hose disconnected.
    (4) After 10 minutes.
    (5) Volume is dependent upon battery voltage and should be checked with battery fully charged. See Fig 2 .
    Fig 2: Measuring Fuel Pump Volume (2.7L BiTurbo & 4.2L V8)
    G00266865Courtesy of AUDI OF AMERICA, INC.
    FUEL PUMP PERFORMANCE (4.2L)

    Application Specification
    System Pressure (1)
    With Engine Idling (2) 50 psi (3.5 bar)
    With Engine Idling (3) 58 psi (4.0 bar)
    Residual Pressure (4) 36 psi (2.5 bar)
    Min. Vol. In 30 Sec. (5) 3.2-3.9 ozs. (95-115 ml.)
    (1) Battery voltage must be 11 volts or more when checking system pressure.
    (2) With fuel pressure regulator vacuum hose connected.
    (3) With fuel pressure regulator vacuum hose disconnected.
    (4) After 10 minutes.
    (5) Volume is dependent upon battery voltage and should be checked with battery fully charged. See Fig 2 .
  3. If fuel pressure is within specification, connect vacuum hose to fuel pressure regulator. Pressure should drop as specified. See appropriate FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is not within specification, check fuel pressure regulator, fuel pump and fuel lines and repair or replace as necessary.
Fig 3: Connecting Fuel Pressure Gauge (TT)
G00077210Courtesy of AUDI OF AMERICA, INC.
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