The procedures for troubleshooting internal-combustion engines are somewhat similar for both diesel and gasoline engines. In many instances, the information that follows will apply to both types of engine. However, it also discusses principal differences. Since most of the internal-combustion engines used by the Navy are diesel, the following sections deal primarily with this type of engine.

This chapter is concerned with troubles that occur both when an engine is starting and running. The troubles are chiefly the kind that can be identified by erratic engine operation, warnings by instruments, or inspection of the engine parts and systems and that can be corrected without major repair or overhaul. There is also a section devoted to the systems of the gasoline engine that are basically different from those of the diesel engine.

Keep in mind that the troubles listed here are general and may or may not apply to a particular diesel engine. When you work with a specific engine, check the manufacturers technical manual and any instructions issued by the Naval Sea Systems Command. An engine may continue to operate even when a serious casualty is imminent. However, symptoms are usually present. Your success as a troubleshooter depends partially upon your ability to recognize these symptoms when they occur. You will use most of your senses to detect trouble symptoms. You may see, hear, smell, or feel the warning of trouble to come. Of course, common sense is also a requisite. Another factor in your success as a troubleshooter is your ability to locate the trouble once you decide something is wrong with the equipment. Then, you must be able to determine as rapidly as possible what corrective action to take. In learning to recognize and locate engine troubles, experience is the best teacher.

Instruments play an important part in detecting engine troubles. You should read the instruments and record their indications regularly. If the recorded indications vary radically from those specified by engine operating instructions, the engine is not operating properly and some type of corrective action must be taken. You must be familiar with the specifications in the engine operating instructions, especially those pertaining to temperatures, pressures, and speeds. You should know the probable effect on the engine when instrument indications vary considerably from the specified values. When variations occur in instrument indications, before taking any corrective action be sure the instruments are not at fault before you try corrective actions on the engine. Check the instruments immediately if you suspect them of being inaccurate.

Periodic inspections are also important in detecting engine troubles. Such inspections will reveal the failure of visible parts, presence of smoke, or leakage of oil, fuel, or water. Cleanliness is probably one of the greatest aids in detecting leakage.

When you secure an engine because of trouble, your procedure for repairing the casualty should follow an established 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 trouble occurs would be an almost endless task. You can find the cause of the trouble much more quickly by following a systematic and logical method of inspection, Genernlly speaking, a well-trained troubleshooter can isolate the trouble by identifying it with one of the engine systems. Once you have associated the trouble with a particular system, the next step is to trace out the system until you find the cause of the trouble. Troubles generally originate in only one system, but remember that troubles in one system may cause damage to another system or to basic engine parts. When a casualty involves more than one system of the engine, trace each system separately and make corrections as necessary. It is obvious that you must know the construction, function, and operation of the various systems as well as the parts of each system for a specific engine before you can satisfactorily locate and remedy troubles.

Even though there are many troubles that may affect the operation of a diesel engine, satisfactory performance depends primarily on sufficiently high compression pressure and injection of the right amount of fuel at the proper time. Proper compression depends basically on the pistons, piston rings, and valve gear, while the right amount of fuel obviously depends on the fuel injectors and their actuating mechanism. Such troubles as lack of engine power, unusual or erratic operation, and excessive vibration may be caused by either insufficient compression or faulty injector action. You can avoid many troubles by following the prescribed instructions for starting and operating the engine, The troubles discussed in the following sections do not comprise a complete list, nor do they all necessarily apply to all diesel engines because of differences in design. Specific information on troubleshooting for all the diesel engines used by the Navy would require more space than is available here. Even though a successful troubleshooter generally associates certain troubles with a particular system or assembly, the following sections discuss troubles according to when they might be encountered, either before or after the engine starts.