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Home >> Audi >> 1990 >> 100 Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Fuel System >> Fuel Pressure (Cis Digital Control) >> System Pressure
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System Pressure

  1. Using Adapter Fittings,connect Pressure Gauge (VW 1318) between line from fuel distributor to cold start valve and test port connection on lower chamber of fuel distributor. See Figure . Test port is sealed by a threaded plug. Bridge fuel pump relay (located on fuse/relay panel) with Jumper Switch (US 4480/3). See Figure for fuel pump relay terminal identifications.
    NOTE: Fuel pump may also be activated by jumping 12 volts to by-pass terminal on fuse/relay panel. See the appropriate WIRING DIAGRAMS article.
  2. Open valve on pressure gauge (points to cold start valve line when open) and activate fuel pump. System pressure must be 68-78 psi (4.7-5.4 kg/cm2 ). If pressure reading is low and fuel pump delivery quantity is good, adjust or replace regulator assembly.
  3. If pressure reading is high, disconnect fuel tank return line from fuel distributor. Repeat test. If reading is correct, check for plugged return line. If reading is incorrect with line open, replace regulator assembly.
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