Engine runs rough and smokes; ECU logs fuel pressure too high; possible surging under load.

Safety: High-pressure fuel can penetrate skin. Do not touch leaking lines. Only trained personnel should service the rail system.

• Connect diagnostics: Use Volvo Penta diagnostic tool to read live rail pressure and compare to specification at idle and under load.
• Inspect wiring: Check the harness and connectors for the rail pressure sensor and pressure control valve on the pump. Look for pin damage, corrosion, or oil contamination. Clean and reseat connectors.
• Check for trapped return lines: Ensure fuel return hoses from the rail and injectors are not kinked or blocked, which can elevate pressure.
• Component testing: If wiring is sound, the rail pressure control valve or relief valve may be stuck. Replacement of these components requires depressurizing the system and following Volvo Penta procedures. This is typically a technician-level repair.