Fuel Delivery – Incorrect Pressures

CIS.029If System Pressure is too low – check fuel pump delivery:

  • Disconnect fuel return line at fuel distributor
  • Place return line in measuring container (one quart capacity)
  • Operate pump for 30 seconds then check delivery quantity

If fuel pump delivery is still too low check for:

  • Fuel line leaks
  • Blocked fuel lines
  • Blocked fuel filter
  • Blocked fuel tank screen
  • Voltage at fuel pump with pump running (at least 11.5v)
  • If everything else is OK replace fuel pump

Adjusting System Pressure

  • System pressure can be adjusted if necessary by adding or subtracting adjusting shims
  • Do not adjust system pressure unless it is out of specifications and unless there is a problem

Early Models

  • Remove carrier plug
  • Check rubber seals
  • Change shims as necessary
  • Replace copper seals
  • Recheck system pressure


Later Models

  • Shims are not available separately, therefore replace pressure regulating valve assembly.

Return to fuel delivery system, page 26.

Add appropriate repair time from SRT Manual


If Control Pressure is too high:

  • Check fuel return line and screen in control pressure regulator for restriction
  • If there is no restriction:
    • REPLACE control pressure regulator

NOTE: Readings may be higher on cars equipped with high altitude kits. Control pressure regulators with the “open” vacuum connection provide higher control pressure as altitude increases. This provides less fuel as air pressure and density decrease.

CIS.030If Control Pressure is too low:

  • Check power supply and ground at control pressure regulator connection with car idling.
  • Test light should glow.
  • If test light glows:
    • REPLACE control pressure regulator

NOTE:Some Audi 5000 engines have a vacuum controlled pressure regulator. For 1978- 1980 models with this regulator the gauge should increase and stabilize at:

  • 3.4-3.8 bar (49-57 psi) with engine idling and vacuum hose connected
  • 2.75-3.05 bar (39-43 psi) with engine idling and vacuum hose
    disconnected and plugged.

Return to fuel delivery system, page 26.

Add appropriate repair time from SRT manual.