KN3 - Check FPRC Vacuum Supply

- Key "OFF".

- Tee in a standard vacuum gauge at the hose between the manifold vacuum source and the Fuel Pressure Regulator Control (FPRC) solenoid input vacuum port.

- Start and idle engine while observing the vacuum gauge needle.

- Was a vacuum signal present?

Yes -- Remove vacuum gauge. Go to KN4. KN4 - Check FPRC Vacuum Hose to Fuel Pressure Regulator

No -- Address base engine vacuum source concern.