Causes:

1. Combustion related:

• Low ignition quality of fuel → higher ignition delay.
• High viscosity of fuel oil injected.
• Incorrect adjustment of fuel pump timing or VIT (Variable Injection Timing).
• Leaky fuel injection valve.
• Improper atomization due to faulty or worn injector nozzle (enlarged holes).

1. Mechanical related:

• Excessive clearances between piston head and connecting rod bearing, piston and liner, crosshead pin and guide shoes, or guide shoes and guide.
• Slackness at piston rod–crosshead attachment or between piston skirt and piston rod.
• Excessive inlet/exhaust valve tappet clearance.
• Excessive backlash in gear or chain drives.

Remedies:

• Ensure proper fuel oil treatment and maintain correct temperature/viscosity.
• Adjust fuel pump timing/VIT correctly as per fuel quality.
• Test, overhaul, and replace faulty fuel injectors or nozzles.
• Carry out regular inspection and calibration of bearings, piston, crosshead, guide shoes, valves, and gear/chain drives.
• Replace defective mechanical components as necessary.

Causes:

• Late injection → reduced Pmax and poor combustion.
• High ignition delay of fuel (low quality, wrong viscosity or temperature).
• Insufficient fuel injection (pump rack stuck at low index, defective fuel injector).
• Fuel oil contamination with water or sludge; air locks in fuel system.
• Faulty fuel pump or poor atomization.
• Loss of compression due to worn piston rings/liner or leaky valves.
• Air supply problems: dirty turbocharger, clogged air cooler/filter, blocked scavenge ports/passages, dirty scavenge space.

Remedies:

• Adjust and calibrate fuel pump timing.
• Free, lubricate, or overhaul a stuck fuel pump rack.
• Ensure proper fuel treatment; drain sludge/water; maintain correct viscosity and temperature.
• Overhaul and pressure-test injectors for proper atomization.
• Maintain liner, piston, and cylinder head condition to restore compression.
• Clean and maintain turbocharger, air cooler, scavenge ports, and scavenge space.

Causes:

• Clogged lubricating oil filter.
• Worn-out lubricating oil pump (gear wear).
• Overheating of lubricating oil.
• Thermostatic control valve stuck or malfunctioning.
• Contaminated lubricating oil.
• Leaks in lubrication system.

Remedies:

• Clean or replace lubricating oil filters.
• Repair or replace worn-out oil pump.
• Increase cooling to reduce oil overheating; overhaul thermostatic valve if faulty.
• Drain contaminated oil and refill with clean oil.
• Locate and repair leaks in the lubrication system.