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Home >> Audi >> 2001 >> S4 Quattro, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel System >> Fuel Pressure Test >> Fuel System Pressure
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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. See FUEL PRESSURE RELEASE  .
  2. Connect Pressure Gauge (VAG 1318) between fuel supply and fuel return lines in engine compartment. See Fig 1 . 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 PRESSURE SPECIFICATIONS (1.8L A4 & S4)

    Function Specification
    System Pressure
    With Engine Idling (1) 50 psi (3.5 bar)
    With Engine Idling (2) 58 psi (4 bar)
    Residual Pressure (3) 36 psi (2.5 bar)
    (1) With fuel pressure regulator vacuum hose connected.
    (2) With fuel pressure regulator vacuum hose disconnected.
    (3) After 10 minutes.
    FUEL PRESSURE SPECIFICATIONS (2.8L)

    Function Specification
    System Pressure
    With Engine Idling (1) 46-55 psi (3.2-3.8 bar)
    With Engine Idling (2) 55-61 psi (3.8-4.2 bar)
    Residual Pressure
    Cold Engine (3) 32 psi (2.2 bar)
    Warm Engine (3) 44 psi (3.0 bar)
    (1) With fuel pressure regulator vacuum hose connected.
    (2) With fuel pressure regulator vacuum hose disconnected.
    (3) After 10 minutes.
    FUEL PRESSURE SPECIFICATIONS (4.2L)

    Function Specification
    System Pressure
    With Engine Idling (1) 50 psi (3.5 bar)
    With Engine Idling (2) 58 psi (4.0 bar)
    Residual Pressure (3) 36 psi (2.5 bar)
    (1) With fuel pressure regulator vacuum hose connected.
    (2) With fuel pressure regulator vacuum hose disconnected.
    (3) After 10 minutes.
  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 1: Connecting Fuel Pressure Gauge (A4 & S4)
G00077211Courtesy of AUDI OF AMERICA, INC.
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