Fueling

Rail Pressure

Fuel pressure in the high-pressure rail feeding the injectors. Dropping under load means the HPFP can't keep up.

Why it matters

Rail pressure drop is the earliest indicator of HPFP limitations. It appears before lean AFR because the ECU compensates with fuel trims first.

Rail pressure should match target within 200 PSI during WOT. Drops below target indicate HPFP limitations.

Pressurizes fuel to ~2,900+ PSI for direct injection. When it can't keep up with demand, fuel pressure drops and the engine runs lean.

Feeds fuel from the tank to the HPFP. If it can't supply enough volume, the HPFP starves and pressure drops.

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