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    Engine Engine Presentation Transcript

    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved. C H A P T E R 1 3 Preventive Maintenance and Troubleshooting Learning Objectives Key Terms After studying this chapter, you will be able to: compression gauge optical tachometer • Perform preventive maintenance on various compression test owner’s manual engine systems, including the crankcase coolant hydrometer preventive maintenance breather, air cleaner, and muffler. differential pressure test reverse flushing digital tachometer service manual • Keep engines clean. filler plug systematic • Change the oil in a four-cycle engine. hot spots troubleshooting • Prepare an engine for storage. loaded oil thread chaser • Describe systematic troubleshooting. • Use manufacturer’s service manuals to determine engine specifications and explain why this information is necessary when servicing a small engine. Methods for cleaning small air-cooled engines Preventive Maintenance vary. Begin by removing any shrouds or engine Certain maintenance tasks must be performed covers obstructing the cooling fins. You can then regularly to keep an engine working properly. blow debris from the fins with compressed air and These tasks come under the heading of preventive use a cleaning solvent to remove any remaining dirt and oil. See Figure 13-1. Alternately, you can scrape S E C T I O N 4 maintenance, because they help prevent prema- ture engine wear and other engine problems. the dirty areas with a piece of wood and wipe them Engine Service with a clean cloth. Various multipurpose spray cleaners are suitable for use on small engines. Chapter 13. Preventive Maintenance and Troubleshooting Engine Cleaning Warning Cleaning a small air-cooled engine periodically Chapter 14. Fuel System Service can help prevent overheating. For proper cooling When using compressed air, be extremely careful where you direct the blast of air. Wear safety goggles. Chapter 15. Ignition and Electrical System Service action, air must pass across the extended metal Never direct the air blast toward skin or clothing. surfaces (cooling fins) of the cylinder block and Chapter 16. Engine Disassembly and Inspection cylinder head. If the cooling fins are insulated by dirt, leaves, and/or grass clippings, engine parts In addition to cleaning cooling fins, be sure to Chapter 17. Cylinder, Crankshaft, and Piston Service will retain most of the combustion heat. Parts will clean the engine crankcase area. This area also trans- expand, probably distort, and possibly seize. There- fers a great deal of engine heat to the surrounding Chapter 18. Camshaft and Valve Train Service fore, all finned surfaces should be cleaned regularly. air. A coating of dirt or oil will insulate the crankcase Chapter 19. Engine Reassembly and Break-In and may contribute to engine overheating. 243
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.244 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 245 The small engine manufacturer will recommend Note oil changes at intervals based on hours of running Some engines do t h e Some engines do not have an oil drain plug. Oil must in il d i l t time. A new engine should have the first oil drained be drained through be drained through the filler hole on these engines. r n g ller e after only a few hours of operation to remove any metallic particles from the crankcase. After that, the time specified may vary from 10–50 hours. Clean the dirt from the drain plug area and Engine oil does not wear out. It always remains then remove the plug with a proper wrench, slippery. However, oil used for many hours of engine Figure 13-5. Allow the oil to drain for approxi- operation becomes contaminated with dirt particles, mately five minutes to remove as much contami- soot, sludge, varnish-forming materials, metal par- nated oil as possible. See Figure 13-6. If the drain ticles, water, corrosive acids, and gasoline. These con- hole is located on the side or top of the engine, tilt taminants eventually render the oil useless. The harm the engine toward the drain hole if possible. When they cause outweighs the lubricating quality of the oil. draining is complete, replace the drain plug. The time interval for oil changes is selected so that the oil never reaches a loaded level of contami-Figure 13-1. nation. Loaded oil cannot absorb any more con-This chain saw engine is being cleaned with taminants and still be an effective lubricant. Whencompressed air. Figure 13-2. oil reaches a loaded condition, varnish deposits Checking the oil is an important part of preventive begin to form on the piston and rings, and sludge maintenance. collects in the crankcase.Checking Oil Level and Condition Crankcase oil in four-cycle engines should be Changing Oilchecked periodically. Preferably, it should be checked Changing engine oil is not difficult. Begin byeach time fuel is added. The engine manufacturer running the engine until it is thoroughly warmedprovides a means of visually inspecting the level and up. Warm oil will drain more completely, and morecondition of the oil. Use the type and viscosity grade contaminants will be removed if the oil is agitated.of oil recommended by the manufacturer and main- Turn off the engine and disconnect the sparktain it at the proper operating level. Socket plug. The oil drain plug is located at a low point To check the oil level in engines equipped with on the crankcase, usually along the outside edge of Figure 13-5.a dipstick, withdraw the dipstick and wipe it dry. the base. See Figure 13-4. This technician is using a socket and ratchet toReinsert the dipstick as far as it will go. Withdraw remove the drain plug. The plug should be turnedit a second time and observe the oil level on the counterclockwise for removal.dipstick. See Figure 13-2. The markings on dipsticks may vary, but all will Plughave a Low (Add) mark and a Full mark. Add oil if the Figure 13-3.level is at or below the Low mark. Do not run the engine A screwdriver can be used to remove the type of oilwith oil showing above the Full mark on the dipstick. If filler plug shown here.the crankcase oil level is high, drain some oil.Caution If the engine oil level drops at an excessive rateOverfilling the crankcaseOverfilling the crankcase with oil can foul plugs and fi i h r ecausecause the engine to use too much oil. engine o e g e (requires the addition of oil frequently), look for the cause. Refer to a troubleshooting chart for the particular engine at hand. Troubleshooting charts Some small gasoline engines do not have dip- are covered later in this chapter. Typical causes ofsticks. Instead, they have a filler plug that threads excess oil consumption are external leaks, worn oilinto the filler hole to seal out dirt and seal in the oil. seals around the crankshaft, worn valve guides, Drain plug Drain plugFigure 13-3 shows the proper method of loosening worn piston rings, or a hot running engine.one type of filler plug. When the plug is removed, The color of used oil is not always an accurate indi- Figure 13-4. Figure 13-6.the oil level should be at the top of the filler hole or cation of its condition. Additives in the oil may change The oil drain plug is located at a low point in the It may take several minutes for all the old oil to drainto a mark just inside the filler hole. its color without decreasing its lubricating qualities. crankcase to permit oil to drain completely. from the engine.
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.246 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 247 If the engine is equipped with a disposable oil Start the engine and allow it to run for a few Cable Housing Spark plugfilter, replace the filter each time the oil is changed. minutes. Then stop the engine and recheck theTo prevent oil leaks, always coat the filter’s O-ring oil level. Add oil as necessary. Finally, inspect theseal with a light coat of clean oil before installing drain plug and oil filter for oil leaks.the filter. See Figure 13-7. Before putting fresh oil in the engine, clean Cautionthe filler opening, funnel, and the top of the oil After changing the oil, wash oily rags or dispose of After changing the a n washcontainer. Be sure to use the type, viscosity grade, them properly. Storing them h y r h them properly. Storing them may cause spontaneousand quantity of oil recommended by the manufac- combustion. Spontaneous combustion occurs when combustion. Spontaneous o o a oturer. Pour the oil in the engine’s crankcase and combustible material self-ignites. combustible material be tthen check the level. See Figure 13-8. If the oil levelis correct, replace the filler cap and reconnect thespark plug lead to the spark plug. If any oil is left in the oil container, cap the container tightly to prevent condensation or contamination. Gasket Lubricating Cables and Linkage Spray lubricant Boot Engine cables and linkage should be lubri- Figure 13-9. Figure 13-10. cated periodically to ensure smooth operation Lubricant can be sprayed between the cable and the When removing a spark plug wire from the plug, pull and reduce the chances of binding and premature housing. on the boot only. Do not pull on the wire itself. wear. Linkage (throttle linkage, governor linkage, etc.) can generally be lubricated by spraying it with Wire-type an appropriate lubricant. feeler gauge Spark Plug Service Note The spark plug should periodically be removed Many manufacturers recommend Many manufacturers recommend silicone-based y ua r m for inspection and cleaned or replaced. Begin by lubricants for e lubricants for use on cables and linkages. Unlike c n o using compressed air to blow dirt away from the petroleum-based products, these lubricants will not petroleum-based o u b base of the spark plug. Remove the spark plug wire attract dirt after they are applied. attract dirt after they a h applied. p from the plug by pulling on the wire’s insulating boot Oil filter only. Do not pull on the wire itself. See Figure 13-10.Figure 13-7. To lubricate cables (throttle cable, engine bale, Install a deep spark plug socket on the plug etc.), place a few drops of the recommended lubri- and carefully turn the ratchet handle counter-A typical disposable oil filter. To prevent leaks, apply a cant between the cable and its housing at the high- clockwise. Unscrew the spark plug and remove itlight film of oil around the O-ring seal before installation. est end of the cable. Allow the lubricant to run down from the cylinder head. between the cable and housing. Lubricant should Carefully examine the electrode end of the flow out of the low end of the cable. If it does not, plug. The electrodes and ceramic insulator should add a few more drops of lubricant and allow it to run be dry. An insulator or electrodes that are wet with Figure 13-11. down the cable. Continue this process until clean fuel or oil may be a sign of serious engine prob- A wire-type feeler gauge is being used to check spark lubricant flows from the bottom end of the cable. lems. A dry insulator that has a beige or gray/tan plug gap. If desired, spray lubricant can be used to lubri- color indicates that the engine is in good condition. cate the cable. Simply spray the lube between the Next, examine the electrodes for any erosion, burn- cable and the housing, and watch for it to exit at ing, or carbon fouling. Refer to Spark Plug Condition the low end of the cable. See Figure 13-9. chart in the Appendix of this text. will specify the proper gap setting. If the gap is too Some manufacturers produce a tool that pro- If the spark plug insulator and electrodes large, carefully bend the outer electrode toward the vides a leak-proof connection between the tube appear to be good (no evidence of fouling or center electrode until the gap is correct. Use the gap from a can of spray lubricant and the cable. When wear), the plug can be reinstalled. If not, install a setting tool. this tool is used, the lubricant is forced under pres- new plug of the correct type. Refer to the manu- Before installing the spark plug, clean the sure through the cable, making lubricating cables facturer’s technical service manuals for the proper external ceramic insulator by wiping it with a cleanFigure 13-8. fast and easy. This type of tool is especially help- replacement spark plug. cloth. Condensation can cause flashover (sparkingClean the area around the filler opening, as well as the ful when lubricating cables that run horizontally Check the electrode gap with a wire-type feeler externally) and erratic running if the insulator hasfunnel, before adding oil. rather than vertically. gauge, Figure 13-11. The engine service manual a coating of dirt on it. If the metal base is rusty,
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.248 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 249clean it on a wire wheel or with a wire brush. If the Air cleaner receptaclethreads are dirty, they should be wiped clean orwire brushed before inserting the plug back intothe spark plug hole. The gasket should be in goodcondition or replaced with a new one. Insert the spark plug in the spark plug hole and Clothturn it clockwise by hand until it stops. Be careful A Bnot to cross thread the spark plug in the hole. If theplug will not turn, do not force it. Remove it andexamine the threads in the hole. If they are dam-aged, a thread chaser (special thread tapping tool)may be needed to clean and correct the threads.If the spark plug turns smoothly by hand untilit seats, tighten the plug with a torque wrench to Air cleaner cover13–15 lb ft. Do not overtighten. C D Figure 13-12. Cover Filter element Examine the spark plug wire for deterioration Figure13-14. The cover on this air cleaner housing is held in place Figure 13-15.before reinstalling it on the spark plug. Heat and by a screw. The sequence for servicing a foam-type filter element isdirt can make the insulation brittle and insula- shown. A—Wash the foam element thoroughly in liquid The pleated paper should face the outside of the airtion cracking can occur. Cracked wire insulation detergent and water. B—Wrap the foam in cloth and cleaner receptacle (away from the engine). Oil-wettedcan allow arcing to metallic parts of the engine squeeze it dry. C—Saturate the foam with clean oil. air cleanerand cause hard starting and erratic running. Oil- D—Squeeze out the excess oil. Pleated paperor fuel-soaked wires will leak current and cause filterweak firing of the plug. The insulating boot shouldbe dry and in good condition. Caution Never use compressed i t l Never use compressed air to clean the paper filter m s d th filter filtAir Cleaner Service because e air can damage because the air can damage the filter element. The n m damaged filter may not prevent fine dirt from entering damaged filter may y prevent The air cleaner should be cleaned before each the engine. the engine. h nseason of operation and at regular intervals there-after. Under severe dust conditions, air filtersshould be cleaned more often. A plugged air filter When installing a pleated paper-type air fil-can cause hard starting, loss of power, and spark ter element, the pleated paper should face theplug fouling. external side of the air cleaner receptacle. See Three types of air cleaners widely used in Figure 13-15. Figure 13-13. Engines designed to be used in dusty conditionssmall gasoline engines are the oil-wetted (plasticfoam element) type, the dry type (pleated paper After the cover is removed, the element can be pulled may have dual-element air cleaners. Dual-element Pre-cleanerelement), and the dual-element type. Each has a from the receptacle. air cleaners use a plastic foam filter pre-cleaner Figure 13-16.different method of cleaning and servicing. that is mounted over a pleated paper filter element. In a dual-element air cleaner, the pre-cleaner must be Begin by removing the screw, wing nut, or See Figure 13-16. When servicing this type of fil- removed before the pleated paper filter can be serviced.other fastening device to uncover the air cleaner The plastic foam should be saturated with clean ter, the pre-cleaner can be washed in detergent andelement. See Figure 13-12. engine oil. After saturating the element, squeeze water and squeezed dry, Figure 13-17. Some pre- When servicing an oil-wetted filter element, excess oil out of the foam. See Figure 13-14. Finally, cleaners must be oiled after they are cleaned. Thethe element can be pulled from the receptacle after reassemble the air filter unit. Follow any special paper filter element should be cleaned by shaking Crankcase Breather Servicethe cover is removed. See Figure 13-13. Be careful instructions found in the owner’s manual for the or replaced.not to drop any dirt into the carburetor throat dur- specific engine and filter. Every engine to be serviced or repaired should If the small gasoline engine has a crankcaseing this procedure. Most dry-type air filter elements (pleated have its air cleaner examined. If the air cleaner ele- breather, the breather assembly should be removed To clean the element, wash it in liquid detergent paper) are designed to be thrown away when they ment or cartridge is damaged or shows signs of and cleaned periodically. The breather is locatedand water. Then rinse the element in clear water. become dirty. Nevertheless, you can clean a pleated restriction, replace it. Worn or damaged mounting over the valve stem chamber. It is held in placeAfter washing the element, wrap it in dry cloth paper filter element by tapping it on a flat surface gaskets and air cleaner gaskets should be replaced with two or more screws.and squeeze it dry. Absorbent toweling works well to dislodge light accumulations of dirt. However, if to prevent dirt and dust from entering the engine To inspect the breather, remove the screws andfor this procedure. the element will not tap clean, it must be replaced. through an improper seal around the filter. the breather assembly. The breather contains a reed
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.250 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 251 This is the task of the exhaust system, which, in Battery Service Corroded terminal small gasoline engines, mainly consists of exhaust port(s) and a small muffler. The battery in a small engine–powered imple- A muffler is designed to reduce noise and ment may be either a maintenance-free battery or allow exhaust gases to escape. When it becomes a conventional lead-acid battery. Check the manu- clogged with carbon soot, gases cannot get out of facturer’s service information to determine which the combustion chamber quickly enough to allow type is being used. fresh air and fuel to enter. This causes a loss in The maintenance-free battery should not be engine power, along with a tendency to overheat. replaced with a conventional lead-acid battery. If clogging is suspected with a sealed muffler, The electrical system is designed exclusively for a install a new muffler and check for improved engine maintenance-free battery and the electrical system efficiency. See Figure 13-19. If a muffler is designed will not work properly with a conventional lead- to be taken apart, it can be disassembled and cleaned acid battery.Figure 13-17. in a solvent to remove soot and other debris. Conventional lead-acid batteries need occa- sional additions of distilled water to keep the elec- Figure 13-20.The foam pre-cleaner can be washed in detergent andwater and squeezed dry. trolyte level above the plates. Fill to the level shown on the case of the battery. Use a bulb syringe to add This battery terminal and cable connection is Locking tab extremely corroded. water and do not overfill. Maintenance-free batter- ies do not need to have fluid added and should notvalve similar to the one shown in Figure 13-18. have the sealed caps removed.The valve allows outward airflow only. Removing, servicing, charging, or installing Inspect the valve to make sure it is not dam- a battery must be done carefully to avoid spillingaged or distorted. If it is, the breather assembly any electrolyte.must be replaced. If applicable, see that the drain Batteries produce hydrogen gas, which is veryhole in the body of the assembly is open. This hole explosive. Keep batteries away from sparks, flame,permits accumulated oil to return to engine. After etc. Charging and using a battery should be doneall components have been inspected, replace dam- in a well-ventilated space. Batteries electrolyteaged gaskets, reinstall the assembly on the engine, contains sulfuric acid, which can cause seriousand tighten the screws. burns to the skin, eyes, or clothing if contact is made. Always wear eye protection when working with batteries.Muffler Service A Batteries are secured in a battery box, tray, or similar device and securely fastened to the imple- Figure 13-21. An engine takes in large quantities of air mixedwith fuel, and then burns the mixture. Unless the ment. The battery is held in position to resist being A parts brush, old toothbrush, or other stiff-bristle brush thrown about during operation. A loose battery should be used to remove the corrosion from the cableengine readily rids itself of the by-products of connectors and battery terminals.combustion, its efficiency will be greatly reduced. would quickly result in a cracked case. This could cause serious damage to the implement and pos- sible injury to the user. When servicing the battery, make sure the battery hold-down is tight and in 4. Rinse the battery and connectors with clear good condition. water and dry the battery case and terminals Corrosion at the battery terminals and cable with absorbent cloths, Figure 13-22. connectors is not uncommon. See Figure 13-20. 5. Coat the terminals with a waterproof The corrosion should be cleaned from the termi- dielectric grease to prevent further corrosion. nals. To clean the terminals, proceed as follows: 6. Reinstall the battery cables on the battery 1. Remove the battery cable from the terminal. terminals. In negative-ground systems, the B 2. Use a solution of baking soda and water positive cable should be connected before the Figure 13-19. to wash the cable connectors and battery negative cable. Valve Drain hole terminals. (One teaspoon of baking soda to Charge a battery only when it needs it. Nor- Locking tabs are often used to prevent muffler fasteners one cup of water).Figure 13-18. mally, the alternator driven by the engine keeps from loosening. A—Before attempting to remove theCrankcase breather elements need periodic fasteners, use a screwdriver to bend the tabs out of the 3. Use a stiff brush to remove the corrosion from the battery charged. If the battery is old and doesinspection. The function of the reed valve is to allow air way. B—Once tabs are bent down, a wrench can be used the cable connectors and battery terminals, not crank the engine, it should be tested and pos-to leave the crankcase, but prevent it from entering. to remove the fasteners securing the muffler to the engine. Figure 13-21. sibly replaced with a new one. A battery that
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.252 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 253 The cooling fi ns that surround the tubes of Begin by thoroughly cleaning the engine. the radiator should be kept clean for efficient Layers of dirt and debris tend to hold moisture, heat transfer. Compressed air or pressurized encouraging the formation of rust and corrosion. water will remove any accumulations that might Add fuel stabilizer to the fuel remaining in prevent air from passing through the fi ns and the tank and fill the tank with fresh gasoline. See across the tubes. To remove debris, direct the Figure 13-24. Fuel stabilizer will help prevent fuel flow of air or water in the opposite direction of breakdown and the formation of gum, varnish, and normal airflow. corrosion in the fuel system. Start the engine and Engine blocks and radiators may be cleaned let it run for a few minutes so stabilized fuel flows periodically by reverse flushing the system with through all parts of the fuel system. If fuel stabilizer pressurized water. Disconnect the hoses from the is not available, run the engine dry of fuel. radiator and the block. Force clean water through Next, drain the oil from the crankcase. Do not the block or the radiator in the direction opposite refill it now. Place a tag on the engine that says No Oil.Figure 13-22. that of normal circulation. This will push loose Rotate the engine so the piston is at bottom ofAfter cleaning, rinse the battery, terminals, and cable sediment out. Continue flushing until the water the cylinder. Remove the spark plug and squirtconnectors with clear water. runs clear. Flushing should be done with the about one tablespoon of clean motor oil through engine stopped and cool. To remove additional the spark plug hole with an oil can. Rotate the rust clinging to inner surfaces, use a commercial engine slowly several times to distribute the oil on cooling system rust remover. Follow the manufac- the cylinder walls. Then replace the spark plug.is low on fluid will not take a full charge. This turer’s instructions. With the spark plug wire disconnected, use thebattery will eventually overheat the plates and When adding coolant, mix water and anti- pull rope to rotate the engine slowly until compres-fail completely. Sulfated plates will cause bat- freeze as specified by the manufacturer. In most sion resistance is felt. Then rotate the engine an Figure 13-23.tery failure also. Refer to the Batteries section in cases, a mixture that contains 50% water and 50% additional one-quarter turn to close off its ports.Chapter 15 of this text for detailed information on Coolant strength can be checked with a hydrometer. antifreeze is recommended. Never use just water. This seals the cylinder and prevents moisture entry.charging batteries. The 50/50 mixture will prevent the coolant from If possible, make sure the throttle is in the off freezing in cold weather. It will also increase the position and the choke is closed. Then store thePressurized Liquid Cooling boiling point of the coolant. Engines operated in saltwater are exposed to engine in a dry, clean area. Always check the strength of the coolant before extremely corrosive conditions. Exposed engine When removing the engine from storage, fill theSystem Service the cold season begins. Weak coolant can freeze, parts require careful maintenance. Flush the cool- crankcase with the recommended type and amount causing damage to the engine block and radiator. ing system with fresh water after each use. Rinse of fresh oil (four-stroke engine). Then remove the The pressurized liquid cooling systems used Coolant strength can be checked with a device the engine with freshwater and wipe all lower unit spark plug and use the pull rope or starter to spinin small engines require maintenance similar to known as a coolant hydrometer. See Figure 13-23. parts with a clean, oily cloth. Ignition leads and the engine rapidly to remove excess oil from the cyl-that employed in the automobile engine. Because To use the hydrometer, simply place the pickup spark plug insulators should also be wiped fre- inder. Clean or replace the spark plug. Then cleanthe combination of water and metal sometimes tube in the engine coolant and squeeze the bulb to quently to prevent an accumulation of salt residue. and oil the air filter or replace cartridge if necessary.produces harmful chemical reactions that attack draw coolant into the hydrometer. Most hydrome-the water jacket, antifreeze containing a chemicalrust inhibitor should be added whenever a sys- ters contain small balls that float in the coolant. The Note number of balls that float indicates the strength oftem is drained and refilled. If rust and scale are Outboard engines Outboard engines used in saltwater should be b r g s the coolant. Some hydrometers have a pointer that removed from the water immediately after operation. removed from e d o immediately mallowed to form and accumulate, the walls of the indicates coolant strength on a scale printed on the If the engine cannot be removed, tilt the gearcase out If the engine cannot e n e n removed, mwater jacket will become insulated. This will cause body of the tester. of the water and rinse it with freshwater. (The gearcase of e water r rinse hengine heat to be retained rather than removed. Scale settling to the bottom may plug water must be removed from the water when not in use.) must e removed t m waterpassages in the cylinder block and clog water tubes Maintaining Outboard Coolingin the radiator. Without free circulation of water,the engine will run hot even when the thermostat Systemsis open. Local hot spots can occur in the engine Outboard engine cooling systems can be Storing an Enginewhen the passages in the block are obstructed. clogged with dirt, sand, or other debris. Flush- In severe cases, water may boil inside the Several precautions should be taken when stor- ing the internal cooling system of an outboard ing an air-cooled engine for an extended period,block, and the steam will prevent water from engine is extremely important. Flushing is donecontacting and cooling inner walls. Then, serious such as when storing an implement for the win- by attaching a freshwater hose to the water scoop ter season. Proper storage procedures will helpoverheating and damage to parts of the engine or by operating the engine in a barrel of freshwater Figure 13-24.are bound to occur. ensure long engine life and easy starting the fol- for several minutes. lowing season. Fuel stabilizer will help prevent fuel system problems.
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.254 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 255 If necessary, fill the fuel tank. If you are servic- Always take a systematic approach when trouble- can be eliminated as a potential problem. In a matter base of the instrument against the running engine.ing a two-stroke engine, make sure the proper fuel- shooting small engines. Systematic troubleshooting of seconds, you have determined that your trouble- Using the dial on the tool, move the thin wire inoil mixture is added to the tank. See Chapter 11 for involves checking and/or testing one component after shooting efforts should be concentrated in the areas or out of the instrument until the wire vibratesadditional information on mixing oil and fuel. another component until the problem is located and of carburetion and ignition. into a fan pattern. Continue to move the wire in Start the engine and let it idle until warm. corrected. There are two basic principles to keep in The engine’s owner can also provide assis- or out until the fan pattern is as wide as possible.Adjust the idle speed if necessary. Increase the mind when trying to pinpoint small engine problems: tance with your troubleshooting efforts. Ask a few When fan pattern is as wide as you can make it,engine speed in the normal manner. Make a brief • Check the easiest things first. questions about the engine’s performance before read the engine speed from the scale on the face oftest run while listening to the engine and watch- • Verify the fundamental operating requirements. it stopped. Relate the answers to the operating the instrument.ing the condition of all parts. requirements. For example, if an engine runs for A digital tachometer can also be used to check 30-45 minutes and then stalls, you should ask if it engine rpm. See Figure 13-26. The lead from thisStoring Liquid-Cooled Engines Check the Easiest Things First restarts immediately after it stops. If the answer particular tachometer is simply wrapped around In addition to the storage precautions cov- is yes, the problem is probably an ignition compo- the spark plug wire. The tachometer will display Always start troubleshooting by checking forered previously, storing liquid-cooled engines for nent that is intermittently experiencing heat-related engine rpm when the engine is running. the simplest, most probable problems first. If anlengthy periods, particularly during winter, calls breakdown. If the engine must cool before it will Another convenient and accurate method of mea- engine will not start, the problem could be some-for special maintenance procedures. If the engine restart, vapor lock or sticking valves are possible suring rpm is with a portable optical tachometer like thing as simple as an empty fuel tank or a discon-has a pressurized system, the coolant must be problems. If a metallic snap is evident in the engine the one in Figure 13-27. Before using this type of nected spark plug wire. Do not start working onstrong enough to protect against freezing at the during the cooling period, the valves are likely to tachometer, a small piece of reflective tape is placed the carburetor or ignition system until you havelowest possible temperatures. be the problem. The time you spend to ask a few on a rotating part of the engine such as the crank- made a few basic checks to determine that a simple If the engine will not be started at any time dur- pertinent questions can save a lot of time in the long shaft, flywheel, or pulley. The optical tachometer remedy will not cure the problem.ing storage, drain the cooling system completely. run by eliminating additional problem possibilities. is aimed at the rotating part. The rpm is read onThen, tag the engine to indicate its drained condition. the digital display in the window. This tachometer When storing outboard engines, remove all Verify the Fundamental Checking RPM can measure from 5–100,000 rpm at a distance up to three feet and at an angle of 45°. These tachom-plugs from the gearcase and drive shaft housing. Operating Requirements eters are small enough to fit in a pocket and weighThis allows accumulated water in the gearcase When servicing small engines, it is often nec-and cooling system to drain off. In order to start and run properly, an engine only 6 ounces. This is a safe method of measur- essary to test or set maximum idle rpm or gover- Failure to take this precaution when winteriz- must meet five fundamental operating require- ing engine rpm, because contact with a hot engine nor rpm. One way to do this is by using a deviceing may result in a cracked cylinder block and/or ments. These requirements include: is not necessary and a safe distance from moving that converts engine vibration from power pulsesgearcase, plus possible damage to water channels • Proper carburetion—Clean, fresh fuel must parts can be maintained. to rpm. See Figure 13-25. To use this tool, place theand tubes. be delivered in the correct proportion with Rock the engine from side to side to make combustion air.certain all water has drained. Refill the gearcase • Correct ignition system operation—A strongwith the type of lubricant specified by the engine ignition spark must be precisely timed for RPM scale Digital tachometermanufacturer. Attend to all other lubrication rec- best performance and efficiency.ommendations made by the manufacturer for care • Adequate lubrication—The proper amount ofof the engine being stored. high-quality lubricating oil must reach critical engine components. • Sufficient cooling—An ample supply of cooling air must reach engine.Systematic Troubleshooting • Proper compression—Compression should have 30–45 psi minimum for starting and Most small engine service and repair jobs can 90 psi minimum for efficient operation andbe done without taking the entire engine apart. sufficient power.If the engine will not start, is hard to start, runs Keep these operating requirements in mind whenrough, or lacks power, troubleshooting may be troubleshooting small gas engines. Through the pro-necessary. Troubleshooting is simply a number of cess of elimination, you can easily isolate problems.tests and steps you go through to find a problem. For example, if an engine will not start but will spin Sometimes the cause of an engine problem is normally, you can eliminate lubrication system prob-easy to find. At other times, checking probable lems because the engine is not locked-up. By spin- Vibrating wire Lead to spark plug wirecauses requires a certain amount of reasoning and ning the engine, you can also determine whether orthe use of the process of elimination. Also, more Figure 13-25. Figure 13-26. not it has sufficient compression. If the engine willthan one fault can exist at the same time, making it not start after it has cooled down, the cooling system You can measure the speed of an engine through the A digital tachometer can be used to check engine rpm.harder to locate the trouble. vibrations caused by power pulses of the piston.
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.256 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 257 Testing Differential Pressure 3. Rotate the engine crankshaft until the piston of the cylinder being tested is at top dead A differential pressure test checks the con- center of the compression stroke. Both valves dition of an engine by measuring leakage from must be closed. the cylinder to other parts of the engine. This test 4. Install the holding fixture supplied with the device and procedure can identify a specific worn tester to prevent the crankshaft from turning or damaged component in the engine that may or during the test. may not be directly related to the cylinder condi- 5. Thread the adaptor into the spark plug hole. tion or rings. The device is designed so that spe- 6. Connect the adaptor on the rubber hose to the cific leakages can be detected and isolated before quick disconnect fitting on the tester. disassembling parts of the engine. 7. Connect an air source of at least 90 psi to the The differential pressure tester requires the tester adaptor. application of air pressure to the cylinder being tested with the piston at top dead center on the Warning compression stroke. Make sure all personnel and objects are clear of the A schematic diagram of the differential pres- engine shaft, belts, pulleys, or other devices connected sure tester is shown in Figure 13-29. As the reg- to the engine shaft. ulated air pressure is applied to one side tester with the air shutoff valve closed, both gauges will read the same. However, when the air shutoff 8. Slowly adjust the regulated pressure gauge on valve is opened and leakage through the cylinder the left with the regulator knob to read 80 psi. increases, the cylinder pressure gauge will record 9. The right-hand gauge indicates the relative a proportionally lower reading. pressure of the cylinder being tested. Due to The differential pressure test can be applied to standard engine clearances and normal wear,Figure 13-27. Figure 13-28. no cylinder is expected to maintain a perfect single cylinder engines or multiple cylinder engines.This optical tachometer can measure rpm without A compression test can indicate the condition of various Each cylinder is tested separately and in the same 80 psi. Generally, a reading of 60 psi or abovecontacting the engine by aiming it at a rotating part that mechanical components of an engine. manner. Use the following procedure to test: is acceptable.has a reflective tape attached. (Monarch Instrument) 1. Run engine until it is warmed up to provide uniform lubrication to cylinder walls and rings. Note An engine producing a compression less than 2. Remove the spark plug wire(s) and spark plug(s). It is important that all cylinders on multi-cylinder t important that p t n a cylinders n engines have engines have a somewhat consistent reading. Good n s vTesting Compression the minimum specified by the manufacturer usu- judgment should be used as to the allowable tolerance judgment should m n o as ally has one or more of the following problems: A cylinder compression test can be a first step between cylinders. Recheck a cylinder that has a between cylinders. Recheck w n y n r c • Leaking cylinder head gasket.toward determining the condition of the upper major reading that is significantly lower (15 psi or more) than reading that s signifi a g y • Warped cylinder head. the other cylinder(s). If a second reading is still low, the other cylinder(s). e y n r second emechanical parts of the engine. This test is especially • Worn piston rings. Regulated Air shutoff pressure gauge valve the cylinder should be suspected of being defective. the cylinder n r suspected pvaluable if an engine lacks power, runs poorly, and • Worn cylinder bore.shows little or no improvement after fuel system and • Damaged piston. Cylinderignition adjustments. To perform a compression test: pressure gauge • Burned or warped valves. 10. By listening for the sound of escaping air, you 1. Run the engine until it is warm. • Improper valve clearance. can determine leakage points in the engine 2. Disconnect all drives to the engine. • Broken or weak valve springs. and the cause of the low pressure reading. A 3. Open the choke and throttle valves wide. To determine whether the valves or rings are hissing at the carburetor intake indicates a 4. Remove the air cleaner. at fault, pour a tablespoonful of SAE 30 oil into the Piston at leaking intake valve, a hissing in the exhaust 5. Remove the spark plug and insert the spark plug hole. Crank the engine several times to top dead suggests a leaking exhaust valve, and hissing compression gauge. See Figure 13-28. spread the oil and repeat the compression test. The center from the crankcase breather indicates leaking 6. Crank the engine as fast as possible and read To air Metering heavy oil will temporarily seal leakage at the rings. piston rings. See Figure 13-30. compressor orifice the gauge. Repeat the test to ensure accuracy. If the compression does not improve, the leakage is due to problems with the valves, cylinder head, NoteNote or piston. This does not disprove a problem with Figure 13-29. If the test indicates If the test indicates a valve problem, first check valve e s n eEngines equippedEngines equipped with compression release n s q p d compression m the rings; the engine may have worn rings in addi- clearance make clearance to make sure the valve is not being held r c k ecamshafts maycamshafts may have to be cranked in reverse rotation s a a tion to its other problems. On the other hand, if the This schematic diagram shows a differential pressure open due o inadequate clearance. open due to inadequate clearance. n u n e eto obtain an accurate reading.to obtain n accurate reading. b n u i compression is much higher than the original test, tester connected to an engine cylinder. (Eastern the leakage is due solely to defective piston rings. Technology Corp.)
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.258 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 259 as well as a variety of tolerances, clearances, and Engine Troubleshooting Chart Air Escaping from: Indication: specifications needed to properly troubleshoot and carburetor intake defective intake valve Cause Remedy service a specific engine. The service procedures found in most manuals Engine fails to start or starts with difficulty exhaust system defective exhaust valve list the steps to take in order to accomplish a task No fuel in tank. Fill tank with clean, fresh fuel. crankcase breather defective piston rings effectively. The detailed drawings of assemblies and Shut-off valve closed. Open valve.Figure 13-30. systems are often exploded views that can help you Obstructed fuel line. Clean fuel screen and line. If necessary, remove and disassemble and reassemble parts in the right order. clean carburetor.The chart shows the location of air leaks and the Troubleshooting charts list the most common Tank cap vent obstructed. Open vent in fuel tank cap.indicated defects. engine troubles along with possible causes and Water in fuel. Drain tank. Clean carburetor and fuel lines. Dry spark suggested remedies. See Figure 13-31. plug and points. Fill tank with clean, fresh fuel. Engine specifications, tolerances, and clear- Engine overchoked. Close fuel shut-off and pull starter until engine starts. ances are also given in a service manual. SeeService Information Figure 13-32. When tolerance specifications show Reopen fuel shut-off for normal fuel flow. Improper carburetor adjustment. Adjust carburetor. Before starting any maintenance, trouble- two values, the actual dimension must be some- where between the two values. In Figure 13-32, for Loose or defective magneto wiring. Check magneto wiring for shorts or grounds; repair ifshooting, or service procedures, the appropriate necessary.service information should be consulted. Basic example, the cylinder bore (diameter) must mea- sure somewhere between 2.1260″ and 2.1265″. Faulty magneto. Check timing, point gap; if necessary, overhaul magneto.maintenance and service information can often be Spark plug fouled. Clean and re-gap spark plug.found in the owner’s manual provided with theimplement or the engine itself. The owner’s man- Spark plug porcelain cracked. Replace spark plug.ual typically includes information on maintenance Engine Identification Poor compression. Overhaul engine.schedules, fluid capacities, and part numbers for In addition to having the correct service infor- No spark at plug. Disconnect ignition cut-off wire at the engine. Crank engine.maintenance components (filters, spark plugs, mation, it is important to identify the exact model If spark at spark plug, ignition switch, or safety switchetc.). It may also include very basic maintenance engine you are servicing. This will allow you to interlock switch is inoperative. If no spark, check magneto.and troubleshooting procedures. For example, locate the proper specifications for the engine. It Crankcase seals and/or gaskets leaking (two cycle only). Replace seals and/or gaskets.the owner’s manual may include instructions for will also help ensure that you order the correct Exhaust ports plugged (two cycle only). Clean exhaust ports.changing an engine air filter or diagnosing a no- repair parts. Engine knocksstart condition. Most engines have a model number displayed Carbon in combustion chamber. Remove cylinder head and clean carbon from head on a sticker affixed to the engine housing or to the and piston.Note engine itself. On some engines, the model number Loose or worn connecting rod. Replace connecting rod.Many engine dMany engine and implement manufacturers make y n n is stamped into the engine block, the metal shroud, Loose flywheel. Check flywheel key and keyway; replace parts ifcopies of their owner’s manual available online. Thesecopies of their owner’s manual e h w n or some other engine component. The model num- necessary. Tighten flywheel nut to proper torque.manuals can often be accessed free of charge.manuals can often u s a e accessed e ber will provide you with specific information about the engine at hand. For example, it will gen- Worn cylinder. Replace cylinder. erally provide you with information on crankshaft Improper magneto timing. Time magneto. A service manual contains more detailed infor- orientation (vertical or horizontal), starter type Engine misses under loadmation than the owner’s manual. Service manuals (recoil start or electric start), carburetor type, etc. Spark plug fouled. Clean and regap spark plug.are often published for each engine type a manu- In addition to the model number, some manu- Spark plug porcelain cracked. Replace spark plug.facturer produces. For example, one manufacturer facturers use ID numbers, serial numbers, or otherpublishes a manual for all variations of the single- Improper spark plug gap. Re-gap spark plug. code numbers that convey additional information.cylinder engines it produces, and another manual See Figure 13-33. These numbers may identify Pitted magneto breaker points. Replace pitted breaker points.for all two-cylinder engines it makes. Some com- unique features of the engine. For example, the Magneto breaker arm sluggish. Clean and lubricate breaker point arm.panies publish service manuals for engines from a engine used on a certain model of lawnmower may Faulty condenser. Check condenser on a tester; replace if defective.variety of manufacturers. have a crankshaft with a special snout to accom- Improper carburetor adjustment. Adjust carburetor. Service manuals can generally be purchased modate the mower’s blade. The numbers may also Improper valve clearance. Adjust valve clearance to recommended specifications.directly from engine manufacturers, as well as provide information on the date of engine manu-from aftermarket publishers. Often, you can pur- Weak valve spring. Replace valve spring. facture, the location of the assembly plant, thechase service manuals at shops that sell engines Reed fouled or sluggish (two cycle only). Clean or replace reed. engine warranty, emissions control compliance,and engine parts. etc. Information on interpreting model numbers, Crankcase seals leak (two cycle only). Replace worn crankcase seals. Service manuals generally include comprehen- as well as other engine identification numbers, can Figure 13-31.sive service procedures, detailed drawings of vari- be found in an appropriate service manual.ous engine assemblies, and troubleshooting charts, Typical troubleshooting chart for small gas engines. (Continued)
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.260 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 261 Engine Troubleshooting Chart Engine Troubleshooting Chart Cause Remedy Cause Remedy Engine lacks power Engine uses excessive amount of oil (four cycle only) Choke partially closed. Open choke. Engine speed too fast. Using tachometer, adjust engine RPM to specifications. Improper carburetor adjustment. Adjust carburetor. Oil level too high. To check level, turn dipstick cap tightly into receptacle Magneto improperly timed. Time magneto. for accurate level reading. Drain excess oil as needed. Worn rings or piston. Replace rings or piston. Oil filler cap loose or gasket damaged causing spillage Replace ring gasket under cap and tighten cap securely. out of breather. Air cleaner fouled. Clean air cleaner. Breather mechanism damaged or dirty causing leakage. Replace breather assembly. Lack of lubrication (four cycle only). Fill crankcase to the proper level. Drain hole in breather box clogged causing oil to spill Clean hole with wire to allow oil to return to crankcase. Valves leaking (four cycle only). Grind valves and set to recommended specifications. out of breather. Reed fouled or sluggish (two cycle). Clean or replace reed. Gaskets damaged or gasket surfaces nicked, causing Clean and smooth gasket surfaces. Always use new Improper amount of oil in fuel mixture (two cycle only). Drain tank; fill with correct mixture. oil to leak out. gaskets. Crankcase seals leak (two cycle only). Replace worn crankcase seals. Valve guides worn excessively thus passing oil into Ream valve guide oversize and install 1/32″ oversize Engine overheats combustion chamber. valve. Engine improperly timed. Time engine. Cylinder wall worn or glazed, allowing oil to bypass Bore, hone, or deglaze cylinder as necessary. rings into combustion chamber. Piston rings and Reinstall new rings, check land clearance, and correct Carburetor improperly adjusted. Adjust carburetor. grooves worn excessively. as necessary. Airflow obstructed. Remove any obstructions from air passages in shrouds. Piston fit undersized. Measure and replace piston as necessary. Cooling fins clogged. Clean cooling fins. Piston oil control ring return holes clogged. Remove oil control ring and clean return holes. Excessive load on the engine. Check operation of associated equipment; reduce Oil passages obstructed. Clean out all oil passages. excessive load. Carbon in combustion chamber. Remove cylinder head and clean carbon from head Figure 13-31. and piston. Lack of lubrication (four cycle only). Fill crankcase to proper level. Tolerances and Clearances for the J-321 Engine Improper amount of oil in fuel mixture (two cycle only). Drain tank; fill with correct mixture. Cylinder bore Max. 2.1265″ Engine surges or runs unevenly Min. 2.1260″ Fuel tank cap vent hole clogged. Open vent hole. Piston skirt diameter Max. 2.1227″ Governor parts sticking or binding. Clean and, if necessary, repair governor parts. Min. 2.1220″ Carburetor throttle linkage or throttle shaft and/or Clean, lubricate, or adjust linkage and deburr throttle Piston ring width Max. .0935″ butterfly binding or sticking. shaft or butterfly. Min. .0925″ Intermittent spark or spark plug. Disconnect ignition cut-off wire at the engine. Crank Piston pin diameter Max. .5001″ engine. If spark, check ignition switch, safety switch, Min. .4999″ and interlock switch. If no spark, check magneto. Check Spark plug gap .030″ wires for poor connections, cuts or breaks. Piston skirt to cylinder Max. .0045″ Improper carburetor adjustment. Adjust carburetor. clearance Min. .0033″ Dirty carburetor. Clean carburetor. Figure 13-33. Figure 13-32. Engine vibrates excessively Identification numbers found on an engine provide Typical tolerance and clearance chart. (Jacobsen Mfg. Co.) valuable information. This sticker displays the engine’s Engine not securely mounted. Tighten loose mounting bolts. build date and serial number. Bent crankshaft. Replace crankshaft. Associated equipment out of balance. Check associated equipment.Figure 13-31.Continued.
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.262 Section 4 Engine Service Chapter 13 Preventive Maintenance and Troubleshooting 263 This causes a loss in engine power, along with a Before starting any maintenance, troubleshoot- 13. To prevent the formation of rust and scale,Summary tendency to overheat. ing, or service procedures, the appropriate service antifreeze containing a rust should be The battery in a small engine–powered imple- information should be consulted. Basic mainte- used in the cooling system. ment may be either a maintenance-free or a con- nance and service information can often be found 14. Outboard engines operated in saltwater are Preventive maintenance involves tasks that ventional lead-acid battery. Conventional lead-acid in the owner’s manual. A service manual contains exposed to conditions.must be performed regularly to keep an engine batteries need occasional additions of distilled wa- more detailed information than the owner’s man-working properly. Cleaning a small air-cooled 15. When storing outboard engines, all plugs ter to keep the electrolyte level above the plates. ual. In addition to having the correct service infor-engine periodically can help prevent overheating. should be removed from the and Fill to the level shown on the case of the battery. mation, it is important to identify the exact modelFor proper cooling action, air must pass across housing. Corrosion at the battery terminals and cable con- engine you are servicing. This will allow you tothe metal surfaces of the cylinder block and cyl- nectors is not uncommon. The corrosion should be locate the proper specifications for the engine. It 16. Systematic troubleshooting involves lookinginder head. If the cooling fins are insulated by cleaned from the terminals. will also help ensure that you order the correct re- for the possible problem first.dirt, leaves, and/or grass clippings, engine parts The pressurized liquid cooling systems used pair parts. 17. In order to run properly, an engine must havewill retain most of the combustion heat. Parts will in small engines require maintenance similar to proper carburetion, correct ignition systemexpand, probably distort, and possibly seize. that employed in the automobile engine. Because operation, adequate lubrication, sufficient Crankcase oil in four-cycle engines should the combination of water and metal sometimes cooling, and .be checked periodically. The small engine manu- produces harmful chemical reactions that attack Review Questions 18. True or False? A compression test can be usedfacturer will recommend oil changes at intervals the water jacket, antifreeze containing a chemical to determine the condition of the spark plug.based on hours of running time. The time speci- rust inhibitor should be added whenever a systemfied may vary from 10–50 hours. Answer the following questions on a separate 19. During a differential pressure test, air is drained and refilled. Outboard engine cooling sheet of paper. leakage heard at the crankcase breather is an Engine cables and linkage should be lubricated systems can be clogged with dirt, sand, or otherperiodically to ensure smooth operation and re- 1. True or False? Preventive maintenance helps indication of defective . debris. Flushing the internal cooling system of anduce the chances of binding and premature wear. outboard engine is extremely important. protect against premature engine wear. 20. Manufacturer’s service manuals contain .Many manufacturers recommend silicone-based Several precautions should be taken when 2. Keeping an engine clean can help prevent A. service procedureslubricants for use on cables and linkages. Unlike storing an air-cooled engine. Proper storage pro- . B. troubleshooting chartspetroleum-based products, these lubricants will cedures will help ensure long engine life and C. tolerance and clearance specifications 3. True or False? Never run an engine if the oilnot attract dirt after they are applied. easy starting the following season. Storing liquid- D. All of the above. level is above full mark. The spark plug should periodically be removed cooled engines for lengthy periods calls for specialfor inspection and cleaned or replaced. Carefully 4. Although oil does not wear out, excess maintenance procedures. If the engine has a pres- make the oil useless.examine the electrode end of the plug. An insula-tor or electrodes that are wet with fuel or oil may surized system, the coolant must be strong enough to protect against freezing at the lowest possible 5. When changing oil, the engine should be . Suggested Activitiesbe a sign of serious engine problems. If the spark A. cold temperatures.plug insulator and electrodes appear to be good, B. warm If the engine will not start, is hard to start, runs 1. Perform preventive maintenance proceduresthe plug can be reinstalled. Examine the spark C. running rough, or lacks power, troubleshooting may be on several engines in your shop. Check the oilplug wire for deterioration before reinstalling it on D. None of the above. necessary. Troubleshooting is simply a number of level and condition. If necessary, change the oilthe spark plug. Heat and dirt can make the insula- tests and steps you go through to find a problem. 6. Many manufacturers recommend using and the filter. Make sure the air filter element,tion brittle and insulation cracking can occur. In order to start and run properly, an engine must -based lubricants on cables and linkages. crankcase breather (if applicable), and cooling The air cleaner should be cleaned before each meet five fundamental operating requirements. 7. True or False? Most manufacturers recommend fins are clean. If engine is equipped with aseason of operation and at regular intervals there- These requirements include proper carburetion, replacing a carbon-fouled spark plug. water cooling system, check engine block andafter. A plugged air filter can cause hard starting, correct ignition system operation, adequate lubri- 8. Name three problems caused by a plugged radiator for signs of rust and corrosion.loss of power, and spark plug fouling. The three cation, sufficient cooling, and proper compression. air filter. 2. Locate several malfunctioning engines. Try totypes of air cleaners widely used in small gasoline A cylinder compression test can be a first stepengines are the oil-wetted type, the dry type, and 9. Why should you refrain from using determine the cause of the problems using the toward determining the condition of the upperthe dual-element type. Each has a different meth- compressed air to clean a pleated paper air systematic troubleshooting method. Remember major mechanical parts of the engine. This test isod of cleaning and servicing. filter element? the five fundamental operating requirements. especially valuable if an engine lacks power, runs If the small gasoline engine has a crankcase poorly, and shows little or no improvement after 10. What two problems can be caused by a 3. Perform a differential pressure test on anbreather, the breather assembly should be removed fuel system and ignition adjustments. A differen- clogged muffler? engine and determine the condition of theand cleaned periodically. The breather is located tial pressure test checks the condition of an engine 11. True or False? All mufflers can be cleaned by rings and valves.over the valve stem chamber. by measuring leakage from the cylinder to other soaking them in solvent. 4. Review several manufacturers’ service manuals. A muffler is designed to reduce noise and allow parts of the engine. This test device and procedure Study trouble code charts and exploded-view 12. When storing an engine for an extendedexhaust gases to escape. When it becomes clogged, can identify a specific worn or damaged compo- assembly drawings. Check maintenance period, should be added to the gasolinegases cannot get out of the combustion chamber nent in the engine that may or may not be directly procedures for engines in your shop. to prevent fuel breakdown and the buildup ofquickly enough to allow fresh air and fuel to enter. related to the cylinder condition or rings. gum, varnish, and corrosion.
    • This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.264 Section 4 Engine ServiceWhen equipment is being refueled or the fuel system is being serviced, care must be taken to minimize spillage.(glennebo/Shutterstock)