learning to recognize and locate engine troubles,experience is the best teacher.Instruments play an important part in detectingengine troubles. You should read the instruments andrecord their indications regularly. If the recordedindications vary radically from those specified byengine operating instructions, the engine is notoperating properly and some type of corrective actionmust be taken. You must be familiar with thespecifications in the engine operating instructions,especially those pertaining to temperatures, pressures,and speeds. You should know the probable effect on theengine when instrument indications vary considerablyfrom the specified values. When variations occur ininstrument indications, before taking any correctiveaction be sure the instruments are not at fault before youtry corrective actions on the engine. Check theinstruments immediately if you suspect them of beinginaccurate.Periodic inspections are also important in detectingengine troubles. Such inspections will reveal the failureof visible parts, presence of smoke, or leakage of oil,fuel, or water. Cleanliness is probably one of the greatestaids in detecting leakage.When you secure an engine because of trouble, yourprocedure for repairing the casualty should follow anestablished pattern, if you have diagnosed the trouble.If you do not know the location of the trouble, find it.To inspect every part of an engine whenever troubleoccurs would be an almost endless task. You can findthe cause of the trouble much more quickly by followinga systematic and logical method of inspection,Genernlly speaking, a well-trained troubleshooter canisolate the trouble by identifying it with one of theengine systems. Once you have associated the troublewith a particular system, the next step is to trace out thesystem until you find the cause of the trouble. Troublesgenerally originate in only one system, but rememberthat troubles in one system may cause damage to anothersystem or to basic engine parts. When a casualtyinvolves more than one system of the engine, trace eachsystem separately and make corrections as necessary. Itis obvious that you must know the construction,function, and operation of the various systems as wellas the parts of each system for a specific engine beforeyou can satisfactorily locate and remedy troubles.Even though there are many troubles that may affectthe operation of a diesel engine, satisfactoryperformance depends primarily on sufficiently highcompression pressure and injection of the right amountof fuel at the proper time. Proper compression dependsbasically on the pistons, piston rings, and valve gear,while the right amount of fuel obviously depends on thefuel injectors and their actuating mechanism. Suchtroubles as lack of engine power, unusual or erraticoperation, and excessive vibration may be caused byeither insufficient compression or faulty injector action.You can avoid many troubles by following theprescribed instructions for starting and operating theengine, The troubles discussed in the following sectionsdo not comprise a complete list, nor do they allnecessarily apply to all diesel engines because ofdifferences in design. Specific information ontroubleshooting for all the diesel engines used by theNavy would require more space than is available here.Even though a successful troubleshooter generallyassociates certain troubles with a particular system orassembly, the following sections discuss troublesaccording to when they might be encountered, eitherbefore or after the engine starts.ENGINE FAILS TO STARTIn general, the troubles that prevent an engine fromstarting are (1) the engine can neither be cranked norbarred over, (2) the engine cannot be cranked, but it canbe barred over, and (3) the engine can be cranked, but itstill fails to start. Figure 3-36 illustrates variousconditions that commonly cause difficulties in cranking,jacking over, or starting the engine.Engine Cannot Be Cranked nor Barred OverMost prestarting instructions for large enginesrequire you to turn the crankshaft one or morerevolutions before applying starting power. If youcannot turn the crankshaft over, check the turning gearto be sure it is properly engaged. If the turning gear isproperly engaged and the crankshaft still fails to turnover, check to see whether the cylinder test valves orindicator valves are closed and are holding water or oilin the cylinder. When the turning gear operates properlyand the cylinder test valves are open but the engine stillcannot be cranked or barred over, check for a seriousproblem. A piston or other part may be seized or abearing may be fitting too tightly. Sometimes you mayneed to remove a part of an assembly to remedy thedifficulty.3-23
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