
TROUBLESHOOTING
Troubleshooting Chart
13-8
BY Service Manual
© 2009 Yanmar Marine International
Engine Knocks
Low Power Output
Engine Overheat
Problem / Symptom
Cause
Action
Excess Fuel Injected
Defective fuel injector
Check / replace fuel injector
High fuel injection pressure
Check / replace fuel pressure regulator /
sensor
Noise Changes with Engine Load
Incorrect or poor quality fuel
Drain and refill tank
Worn crankshaft / bearings
Repair as necessary
Broken piston / rings
Repair as necessary
Problem / Symptom
Cause
Action
Miscellaneous
Clogged intake air filter
Replace
Leaking cylinder head gasket
Replace
Damaged turbocharger
Replace
Incorrect propeller
Replace
Excessive exhaust backpressure
Remove obstruction
Fuel
Plugged fuel filter(s)
Replace as necessary
Faulty fuel supply pump
Replace
Low Fuel Injection Pressure
Defective fuel pressure regulator /
sensor
Check / replace
Worn high-pressure fuel pump
Check / replace
Injection timing is incorrect
ECU / software problem
Low RPM at Wide Open Throttle
Propeller pitch too great
Replace
Engine overheated
Reduce load / repair cooling system
Damaged turbocharger
Replace
Problem / Symptom
Cause
Action
Instrument Shows High Temperature
Clogged seawater inlet
Clean
Low coolant level
Fill with coolant / inspect for leak
Clogged seawater filter (if equipped)
Clean
Clogged hydraulic cooler
Clean
Seawater pump worn or damaged
Repair / replace as necessary
Defective sensor / instrument
Repair as necessary
Defective thermostat
Replace
Damaged closed coolant pump
Replace
Combustion gas leakage (causes loss of
coolant)
Repair as necessary
Seawater pump belt slips or pump pulley
loose on pump shaft
Repair as necessary
Clogged heat exchanger
Clean