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2009 AUDI R8
5.2L V10 (Gen 1, 525hp)•AWD•AUTOMATIC•gas•BUJ
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Repairs0Labor492Torque4246Fluid9DTC1087Battery1Maintenance0Recalls0
P3657high severityPowertrain

GDI Fuel System Priming Pump Performance

on 2009 Audi R8 5.2L V10 (Gen 1, 525hp) · AWD

What this code means

The low-pressure electric fuel pump that primes the GDI high-pressure fuel system is not delivering adequate fuel volume or pressure to the HP pump inlet.

Symptoms

  • Extended cranking time
  • Hard start after sitting
  • Fuel rail slow to build pressure
  • Engine stalling after start
  • HP pump cavitation noise

Common causes

  • Weak fuel pump motor
  • Clogged fuel filter
  • Fuel pump check valve leak
  • Fuel tank pickup sock restricted
  • Fuel pump relay intermittent

Diagnostic steps

  1. Measure fuel pressure at HP pump inlet
  2. Test electric fuel pump current draw
  3. Check fuel filter restriction
  4. Test fuel pump check valve hold pressure
  5. Inspect fuel pump relay and wiring

Repair notes

Replace low-pressure fuel pump or fuel filter. GDI systems are sensitive to feed pressure - even slight deficiency causes HP pump issues.

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