Fuel pumps depend on a stable liquid supply.

If local pressure becomes too low, vapor bubbles can form and collapse within the fuel flow.

This phenomenon is known as cavitation.

Cavitation Is Different From External Air Entry

Air ingress introduces gas from outside the system.

Cavitation creates vapor locally because of pressure conditions within the fluid.

The two conditions may produce similar hydraulic symptoms but have different causes.

Conditions That Can Encourage Cavitation

Possible contributors include:

• excessive inlet restriction;
• insufficient feed pressure;
• high fuel temperature;
• restricted filters;
• undersized or damaged supply lines.

Why Pump Performance Can Change

Cavitation can disrupt pump filling and may contribute to unstable delivery.

Possible symptoms include:

• noise;
• pressure fluctuation;
• reduced fuel delivery.

These symptoms can then be misinterpreted as injector or pressure-control faults.

Start With the Pump Inlet

When cavitation is suspected, investigate:

Tank → Filter → Supply Line → Feed Pressure → Pump Inlet

rather than beginning only on the high-pressure side.

Conclusion

Stable high-pressure generation begins with stable low-pressure fuel supply.

Cavitation is one reason inlet conditions should be verified during difficult pressure-related diagnoses.