Fuel System
6 LessonsUnderstand fuel delivery from tank to injector — GDI, port injection, and everything in between.
Overview
Modern fuel systems operate at pressures from 40 PSI (port injection) to over 2,000 PSI (GDI). This module covers fuel pumps, fuel pressure regulators, injector types, fuel rails, returnless systems, and the diagnostic techniques needed for both port and direct injection systems.
Key Components
- In-tank fuel pump and module
- Fuel pressure regulator
- Fuel injectors (port and direct)
- Fuel rail and lines
- High-pressure fuel pump (GDI)
How It Works
The fuel pump delivers fuel from the tank to the injectors at a regulated pressure. The PCM controls injector pulse width (how long each injector opens) to meter the exact amount of fuel needed. GDI systems add a high-pressure pump that boosts pressure for direct injection into the combustion chamber.
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Join the Nation — FreeCommon Problems
- Weak fuel pump causing lean conditions under load
- Clogged injectors causing misfire
- GDI carbon buildup on intake valves
- Fuel pressure regulator diaphragm leak
- Contaminated fuel causing multiple issues
Diagnostic Tips
- Fuel pressure test under load, not just key-on
- Injector balance test identifies weak injectors
- Listen for fuel pump prime with key-on
- Fuel trim data is your best friend for fuel system diagnosis
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