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2008 AUDI S5
4.2L V8•AWD•AUTOMATIC•gas•BNS
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Repairs0Labor494Torque4251Fluid10DTC1087Battery1Maintenance0Recalls0
P3650high severityPowertrain

GDI High-Pressure Fuel Pump Performance

on 2008 Audi S5 4.2L V8 · AWD

What this code means

The gasoline direct injection (GDI) high-pressure fuel pump is not maintaining the commanded fuel rail pressure. GDI systems operate at 200-3000+ PSI.

Symptoms

  • Check Engine Light
  • Long crank time
  • Rough idle
  • Reduced power
  • Engine stalling
  • Fuel smell from engine bay

Common causes

  • Worn fuel pump cam follower
  • Internal pump wear
  • Low feed pressure from tank pump
  • Fuel pump driver module fault
  • Contaminated fuel

Diagnostic steps

  1. Monitor fuel rail pressure vs commanded
  2. Check low-pressure feed pump output
  3. Inspect cam follower for wear
  4. Test fuel pump driver module
  5. Check fuel quality

Repair notes

Replace high-pressure fuel pump and cam follower together. Always replace the follower to prevent repeat failure. Check camshaft lobe for wear.

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