High Pressure Fuel Pump
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.
Why it matters
HPFP failure is one of the most common hardware bottlenecks on modified cars. A failing HPFP under WOT causes lean conditions that the ECU may not fully compensate for.
What to look for
HPFP pressure should track target closely under WOT. A deviation of more than 200 PSI below target is a warning. More than 500 PSI is critical. If pressure oscillates rapidly, the pump may be cavitating.
Related terms
Feeds fuel from the tank to the HPFP. If it can't supply enough volume, the HPFP starves and pressure drops.
The ratio of air to fuel in the combustion chamber. Lower number = richer (more fuel). Higher number = leaner (less fuel).
What percentage of available time the fuel injectors are open. Above ~85% means the injectors are near maximum capacity.
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