Repair or Replace Fuel System Components to Correct Lean Air/Fuel Mixture

Safety Precautions: Ensure the engine is completely cool, the engine compartment is ventilated to remove fuel vapors, and the battery is disconnected. Wear safety glasses and fuel-resistant gloves.

Required Tools: Fuel pressure gauge, fuel line wrenches, replacement fuel filter, and compatible high-pressure fuel pump.

1. Replace the fuel filter: Locate the inline fuel filter, place a rag underneath to catch residual fuel, use fuel line wrenches to disconnect the lines, and install the new filter ensuring the flow direction arrow points toward the engine.
2. Test fuel pump output: Connect a fuel pressure gauge to the high-pressure fuel rail test port.
3. Verify pressure: Crank the engine or cycle the ignition to prime the pump and observe the gauge; the system must maintain 39 PSI (±3 PSI) under load.
4. Replace fuel pump: If the pressure remains below the specified range despite a new filter, disconnect the electrical harness and fuel lines from the fuel pump assembly, remove the mounting hardware, and install a new high-pressure fuel pump unit.
5. Final Verification: Reconnect the battery, prime the system, check for any fuel leaks at the connections, and perform a sea trial at high speed to confirm the engine no longer knocks and the spark plugs show a healthy, tan-colored deposit rather than a white/clean appearance.