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Troubleshooting Guide for Large 2 Stroke Marine IC Engines

Updated on July 24, 2013
Large 2 Stroke Marine Internal Combustion Engine
Large 2 Stroke Marine Internal Combustion Engine

Engine Fails to Turn on Air After Moving Starting Lever

Possible causes are:

  • Pressure in air bottles too low
  • Isolating valve on air bottles closed
  • Isolating valve on air distributor closed
  • Control valve for air distributor sticking
  • Low control air pressure
  • Main starting air valve jammed
  • Turning gear interlock
  • Reversing not taken place
  • Bursting disc on starting air line damaged
  • Valve for operating 'AUTO AIR START VALVE' not operating
  • Valve for operating air to 'DISTRIBUTOR' not operating

Engine Turns on Air but Not Firing

Possible causes are:

  • Regulating shaft held back by stop cylinder
  • Shut-down piston of fuel pumps
  • Valve supplying air to 'PUNCTURE VALVE' not cut off
  • Boost air not supplied to Governor
  • Governor air booster does not supply adequate oil pressure
  • Pre-set control air signal to Governor too low
  • Fuel pump index too low
  • Fuel filter blocked
  • Auxiliary blower not functioning

Exhaust Temperatures of All Units High

Possible causes are:

  • Scavenge air temperature high, due to inefficient air cooler or scavenge fire
  • Fouled scavenge air and exhaust passages
  • Bad combustion due to fuel characteristics, inadequate treatment of fuel
  • Wrong timing

Inspection of Piston, Piston Rings, Liner, Scavenge Space, etc. Through Scavenge Ports
Inspection of Piston, Piston Rings, Liner, Scavenge Space, etc. Through Scavenge Ports

Exhaust Temperatures of Any Particular Unit High

Possible causes are:

  • Defective fuel injector
  • Leaking exhaust valve
  • Blow-past
  • Slipped or wrongly adjusted fuel cam
  • Defective pyrometer

Engine RPM Falling

Possible causes are:

  • Air lock due to inadequate venting / gassing of fuel
  • Booster pump pressure low
  • Defective fuel pumps / fuel injectors
  • Water in the fuel
  • Insufficient air due to turbocharger problem
  • Scavenge fire
  • Fouling of the hull
  • Combustion characteristics of the fuel
  • Problem in the governor

Smoky Exhaust

Possible causes are:

  • Turbocharger rpm low
  • Insufficient air due to choked inlet filters / irregular running of turbocharger
  • Defective fuel injectors
  • Scavenge fire
  • Incorrect fuel timing
  • Afterburning
  • Incorrect viscosity of fuel before injectors

Piston Disassembled From Cross Head
Piston Disassembled From Cross Head

Hot Spots in Crankcase

Possible causes are:

  • Inadequate purification of the crankcase oil
  • Bearing overheating
  • Touching of rubbing / sliding surfaces
  • Scavenge fire

Reduced Compression Pressure

Possible causes are:

  • Defective or worn-out piston rings
  • Burnt piston crown
  • Worn or oval cylinder liner
  • Damaged or burnt exhaust valve
  • Incorrect exhaust valve timing
  • Insufficient scavenging

Loss of Power

Possible causes are:

  • Fuel rack settings incorrect
  • Insufficient air
  • Faulty fuel injectors
  • Faulty fuel pumps
  • Loss of compression
  • Governor malfunctioning
  • Fouling of hull
  • Change in fuel timings
  • Change in VIT rack / settings

Cylinder Liner Inspection
Cylinder Liner Inspection

Over Speed

Possible causes are:

  • Fuel racks stuck
  • Fault in governor
  • Racing of propeller
  • Knocking
  • Possible causes are:
  • Fuel injection timing incorrect
  • Faulty fuel injector
  • Worn out bearings
  • Excessive play between piston and liner
  • Fuel characteristics


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