CHAPTER 3INTERNAL COMBUSTION ENGINESThis chapter is designed to help you understand themaintenance and repair of internal combustion engines.You as an EN2 should be able to describe the basicprocedures used to test and repair diesel engines. Also,you should be able to identify the procedures used totroubleshoot diesel and gasoline engines. This chapterwill cover the general procedures used to repair andoverhaul gasoline engines; the procedures used toinspect, test, and repair jacking gear; and the proceduresused to troubleshoot and repair fuel and oil purifiers.To help ensure that an engine will operateefficiently, you must follow its preventive maintenanceschedule. By following the preventive maintenanceschedule, you will reduce engine casualties and help theengine achieve its normal number of operating hoursbetween overhaul periods.When you must finally perform an engine repair oroverhaul, take the following precautions:l Plan the work in definite steps, so you canperform it smoothly.l Have the necessary tools and parts on handbefore you begin a repair or overhaul.l Have the necessary forms ready to record theclearances, dimensions, and other vital measurementreadings that must be kept as part of the engine’s history.l Always check precision measuring instrumentsbefore you use them; then recheck your readings. Thefirst reading may not be correct.l Keep the work area clean. Do not allow oil toaccumulate on the deck or on the tools. Place the toolsor parts neatly away from the immediate area.The test, maintenance, and repair procedurespresented in this chapter are general in nature. Thespecific procedures vary with different engines. Beforeyou begin a maintenance or repair procedure, consultthe manufacturer’s technical manual or the equipment’spreventive maintenance schedules. They are valuablesources of information on tests, maintenance, andrepairs.INSPECTING AND TESTING THEENGINE FRAME OR BLOCKBefore you begin an inspection or test, make surethe outside of the engine is cleaned thoroughly. This willhelp you spot cracks, leaks, and other problems moreeasily than if the engine is dirty. By cleaning the engine,you will also help prevent dirt and other contaminantsfrom entering and damaging parts and accessories of theengine.Some of the inspections and tests you may performare listed in the following sections.VISUAL INSPECTIONSInspect the top surface of the cylinder block, the topand bottom crankcase flanges, and the oil pan forwarpage. You can use a straightedge, a feeler gauge, anda good light. Figure 3-1 illustrates how to use astraightedge and a feeler gauge to check the top surfaceof the cylinder block Compare your measurements tothe manufacturer’s specifications to determine if thesurface is warped.Visually inspect the cylinder block for cracks,breaks, or other damage.MEASUREMENTSVisually inspect the engine block’s bolts todetermine if they are bent, broken, or worn.Figure 3-1.—Checking the top surface of a typical cylinder block.3-1
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