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The chart below shows the most common questions asked by owners of Detroit Diesel® engines 12V149 Natural when trying to troubleshoot why their engines underperform. It categorizes areas of possible malfunction, likely cause and recommended action to bring your new, rebuilt or used Detroit Diesel® engine back to proper operation. The chart will give you confidence when speaking with your Detroit Diesel® engine mechanic or ordering parts. As a quick reference guide only, the chart must not be thought of as a substitute for the use of your Detroit Diesel® engine 12V149 Natural Owner's operating or service manual. PROBLEM POSSIBLE REASON CHECK
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Engine will not start
Lack of air intake or restricted air intake
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Broken blower shaft
Worn out blower shaft
Defective fuel pump
Defective starter
Discharged battery
High exhaust back pressure
Black smoke coming out of engine
Defective injector
Contaminated fuel
Broken or worn cylinder parts
Engine overloaded
Faulty intercooler or aftercooler (for turbo engines only)
White smoke coming out of engine
Broken piston ring
Incorrectly installed ring set
Defective injector
Fuel quality or grade
Long idle periods
Broken or bent push rod
Injector or governor improperly adjusted
Low engine oil pressure
Water in engine oil pan
Fuel in engine oil pan
Defective oil cooler
Engine overloaded
Crankcase overfilled
Low engine RPM
Improperly working injector
Governor calibration
Hi engine RPM
Governor calibration
Engine overheating
Defective fresh water pump
Defective raw water pump (marine engines only)
Defective thermostat or thermostat seal
Clogged radiator or heat exchanger (marine engine only)
Grey smoke coming out of engine
Long idle periods
Defective intercooler or aftercooler (for turbo engine only)
Restricted air intake
Defective injector
Contaminated fuel
Blower or turbocharger seals leaking
Geartrain makes noises
Low oil level
Engine driven accesories
Damage main or rod bearing
