Chapter 13 - Goodheart
Contents
1. Boot Figure 13 10 When removing a spark plug wire from the plug pull on the boot only Do not pull on the wire itself Wire type feeler gauge F A wire type feeler gauge is being used to check spark plug gap igure 13 11 will specify the proper gap setting If the gap is too large carefully bend the outer electrode toward the center electrode until the gap is correct Use the gap setting tool Before installing the spark plug clean the external ceramic insulator by wiping it with a clean cloth Condensation can cause flashover sparking externally and erratic running if the insulator has 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 clean it on a wire wheel or with a wire brush If the threads are dirty they should be wiped clean or wire brushed before inserting the plug back into the spark plug hole The gasket should be in good condition or replaced with a new one Insert the spark plug in the spark plug hole and turn it clockwise by hand until it stops Be careful not to cross thread the spark plug in the hole If the plug will not turn do not force it Remove it and examine 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 until it2. If the engine is equipped with a disposable oil filter replace the filter each time the oil is changed To prevent oil leaks always coat the filter s O ring seal with a light coat of clean oil before installing the filter See Figure 13 7 Before putting fresh oil in the engine clean the filler opening funnel and the top of the oil container Be sure to use the type viscosity grade and quantity of oil recommended by the manufac turer Pour the oil in the engine s crankcase and then check the level See Figure 13 8 If the oil level is correct replace the filler cap and reconnect the spark plug lead to the spark plug Gasket Figure 13 7 A typical disposable oil filter To prevent leaks apply a light film of oil around the O ring seal before installation Figure 13 8 Clean the area around the filler opening as well as the funnel before adding oil Section 4 Engine Service Start the engine and allow it to run for a few minutes Then stop the engine and recheck the oil level Add oil as necessary Finally inspect the drain plug and oil filter for oil leaks changing the oil wash oily rags or dispose of perly Storing them may cause spontaneous Spontaneous combustion occurs when stible material self ignites If any oil is left in the oil container cap the container tightly to prevent condensation or contamination Lubricating Cables and Linkage Engine cables and linkage should be lu
3. cess of elimination you can easily isolate problems For example if an engine will not start but will spin normally you can eliminate lubrication system prob lems because the engine is not locked up By spin ning the engine you can also determine whether or not it has sufficient compression If the engine will not start after it has cooled down the cooling system Chapter 13 Preventive Maintenance and Troubleshooting can be eliminated as a potential problem In a matter of seconds you have determined that your trouble shooting efforts should be concentrated in the areas of carburetion and ignition The engine s owner can also provide assis tance with your troubleshooting efforts Ask a few questions about the engine s performance before it stopped Relate the answers to the operating requirements For example if an engine runs for 30 45 minutes and then stalls you should ask if it restarts immediately after it stops If the answer is yes the problem is probably an ignition compo nent that is intermittently experiencing heat related breakdown If the engine must cool before it will restart vapor lock or sticking valves are possible problems If a metallic snap is evident in the engine during the cooling period the valves are likely to be the problem The time you spend to ask a few pertinent questions can save a lot of time in the long run by eliminating additional problem possibilities Checking RPM When servicing
4. sional additions of distilled water to keep the elec trolyte level above the plates Fill to the level shown on the case of the battery Use a bulb syringe to add water and do not overfill Maintenance free batter ies do not need to have fluid added and should not have the sealed caps removed Removing servicing charging or installing a battery must be done carefully to avoid spilling any electrolyte Batteries produce hydrogen gas which is very explosive Keep batteries away from sparks flame etc Charging and using a battery should be done in a well ventilated space Batteries electrolyte contains sulfuric acid which can cause serious burns to the skin eyes or clothing if contact is made Always wear eye protection when working with batteries Batteries are secured in a battery box tray or similar device and securely fastened to the imple ment The battery is held in position to resist being thrown about during operation A loose battery 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 good condition Corrosion at the battery terminals and cable connectors is not uncommon See Figure 13 20 The corrosion should be cleaned from the termi nals To clean the terminals proceed as follows 1 Remove the battery cable from the terminal 2 Use a solution of baking soda and wate
5. prevent air from passing through the fins and across the tubes To remove debris direct the flow of air or water in the opposite direction of normal airflow Engine blocks and radiators may be cleaned periodically by reverse flushing the system with pressurized water Disconnect the hoses from the radiator and the block Force clean water through the block or the radiator in the direction opposite that of normal circulation This will push loose sediment out Continue flushing until the water runs clear Flushing should be done with the engine stopped and cool To remove additional rust clinging to inner surfaces use a commercial cooling system rust remover Follow the manufac turer s instructions When adding coolant mix water and anti freeze as specified by the manufacturer In most cases a mixture that contains 50 water and 50 antifreeze is recommended Never use just water The 50 50 mixture will prevent the coolant from freezing in cold weather It will also increase the boiling point of the coolant Always check the strength of the coolant before the cold season begins Weak coolant can freeze causing damage to the engine block and radiator Coolant strength can be checked with a device known as a coolant hydrometer See Figure 13 23 To use the hydrometer simply place the pickup tube in the engine coolant and squeeze the bulb to draw coolant into the hydrometer Most hydrome ters contain small balls that float in the coo
6. and fail completely Sulfated plates will cause bat tery failure also Refer to the Batteries section in Chapter 15 of this text for detailed information on charging batteries Pressurized Liquid Cooling System Service The pressurized liquid cooling systems used in small engines require maintenance similar to that employed in the automobile engine Because the combination of water and metal sometimes produces harmful chemical reactions that attack the water jacket antifreeze containing a chemical rust inhibitor should be added whenever a sys tem is drained and refilled If rust and scale are allowed to form and accumulate the walls of the water jacket will become insulated This will cause engine heat to be retained rather than removed Scale settling to the bottom may plug water passages in the cylinder block and clog water tubes in the radiator Without free circulation of water the engine will run hot even when the thermostat is open Local hot spots can occur in the engine when the passages in the block are obstructed In severe cases water may boil inside the block and the steam will prevent water from contacting and cooling inner walls Then serious overheating and damage to parts of the engine are bound to occur Section 4 Engine Service The cooling fins that surround the tubes of the radiator should be kept clean for efficient heat transfer Compressed air or pressurized water will remove any accumulations that might
7. oil may be a sign of serious engine problems If the spark plug insulator and electrodes appear to be good the plug can be reinstalled Examine the spark plug wire for deterioration before reinstalling it on the spark plug Heat and dirt can make the insula tion brittle and insulation cracking can occur The air cleaner should be cleaned before each season of operation and at regular intervals there after A plugged air filter can cause hard starting loss of power and spark plug fouling The three types of air cleaners widely used in small gasoline engines are the oil wetted type the dry type and the dual element type Each has a different meth od of cleaning and servicing If the small gasoline engine has a crankcase breather the breather assembly should be removed and cleaned periodically The breather is located over the valve stem chamber A muffler is designed to reduce noise and allow exhaust gases to escape When it becomes clogged gases cannot get out of the combustion chamber quickly enough to allow fresh air and fuel to enter Section 4 Engine Service This causes a loss in engine power along with a tendency to overheat The battery in a small engine powered imple ment may be either a maintenance free or a con ventional lead acid battery Conventional lead acid batteries need occasional additions of distilled wa ter to keep the electrolyte level above the plates Fill to the level shown on the case of the batter
8. problem is located and corrected There are two basic principles to keep in mind when trying to pinpoint small engine problems e Check the easiest things first e Verify the fundamental operating requirements Check the Easiest Things First Always start troubleshooting by checking for the simplest most probable problems first If an engine will not start the problem could be some thing as simple as an empty fuel tank or a discon nected spark plug wire Do not start working on the carburetor or ignition system until you have made a few basic checks to determine that a simple remedy will not cure the problem Verify the Fundamental Operating Requirements In order to start and run properly an engine must meet five fundamental operating require ments These requirements include e Proper carburetion Clean fresh fuel must be delivered in the correct proportion with combustion air e Correct ignition system operation A strong ignition spark must be precisely timed for best performance and efficiency e Adequate lubrication The proper amount of high quality lubricating oil must reach critical engine components e Sufficient cooling An ample supply of cooling air must reach engine e Proper compression Compression should have 30 45 psi minimum for starting and 90 psi minimum for efficient operation and sufficient power Keep these operating requirements in mind when troubleshooting small gas engines Through the pro
9. seats tighten the plug with a torque wrench to 13 15 Ib ft Do not overtighten Examine the spark plug wire for deterioration before reinstalling it on the spark plug Heat and dirt can make the insulation brittle and insula tion cracking can occur Cracked wire insulation can allow arcing to metallic parts of the engine and cause hard starting and erratic running Oil or fuel soaked wires will leak current and cause weak firing of the plug The insulating boot should be dry and in good condition Air Cleaner Service The air cleaner should be cleaned before each season of operation and at regular intervals there after Under severe dust conditions air filters should be cleaned more often A plugged air filter can cause hard starting loss of power and spark plug fouling Three types of air cleaners widely used in small gasoline engines are the oil wetted plastic foam element type the dry type pleated paper element and the dual element type Each has a different method of cleaning and servicing Begin by removing the screw wing nut or other fastening device to uncover the air cleaner element See Figure 13 12 When servicing an oil wetted filter element the element can be pulled from the receptacle after the cover is removed See Figure 13 13 Be careful not to drop any dirt into the carburetor throat dur ing this procedure To clean the element wash it in liquid detergent and water Then rinse the element in clear wat
10. small engines it is often nec essary to test or set maximum idle rpm or gover nor rpm One way to do this is by using a device that converts engine vibration from power pulses to rpm See Figure 13 25 To use this tool place the RPM scale Vibrating wire Figure 13 25 You can measure the speed of an engine through the vibrations caused by power pulses of the piston base of the instrument against the running engine Using the dial on the tool move the thin wire in or out of the instrument until the wire vibrates into a fan pattern Continue to move the wire in or out until the fan pattern is as wide as possible When fan pattern is as wide as you can make it read the engine speed from the scale on the face of the instrument A digital tachometer can also be used to check engine rpm See Figure 13 26 The lead from this particular tachometer is simply wrapped around the spark plug wire The tachometer will display engine rpm when the engine is running Another convenient and accurate method of mea suring rpm is with a portable optical tachometer like the one in Figure 13 27 Before using this type of tachometer a small piece of reflective tape is placed on a rotating part of the engine such as the crank shaft flywheel or pulley The optical tachometer is aimed at the rotating part The rpm is read on the digital display in the window This tachometer can measure from 5 100 000 rpm at a distance up to three f
11. test can be used to determine the condition of the spark plug 19 During a differential pressure test air leakage heard at the crankcase breather is an indication of defective 20 Manufacturer s service manuals contain A service procedures B troubleshooting charts C tolerance and clearance specifications D All of the above Suggested Activities 1 Perform preventive maintenance procedures on several engines in your shop Check the oil level and condition If necessary change the oil and the filter Make sure the air filter element crankcase breather if applicable and cooling fins are clean If engine is equipped with a water cooling system check engine block and radiator for signs of rust and corrosion 2 Locate several malfunctioning engines Try to determine the cause of the problems using the systematic troubleshooting method Remember the five fundamental operating requirements 3 Perform a differential pressure test on an engine and determine the condition of the rings and valves 4 Review several manufacturers service manuals Study trouble code charts and exploded view assembly drawings Check maintenance procedures for engines in your shop This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved Pres Section 4 Engine Service g aA Ge Ge aN aca NN Ri hat NS nly nn aenunnn When equipment is being refueled or the f
12. This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved Learning Objectives After studying this chapter you will be able to e Perform preventive maintenance on various engine systems including the crankcase breather air cleaner and muffler e Keep engines clean e Change the oil in a four cycle engine e Prepare an engine for storage e Describe systematic troubleshooting e Use manufacturer s service manuals to determine engine specifications and explain why this information is necessary when servicing a small engine Preventive Maintenance Certain maintenance tasks must be performed regularly to keep an engine working properly These tasks come under the heading of preventive maintenance because they help prevent prema ture engine wear and other engine problems Engine Cleaning Cleaning a small air cooled engine periodically can help prevent overheating For proper cooling action air must pass across the extended metal surfaces cooling fins of the cylinder block and cylinder head If the cooling fins are insulated by dirt leaves and or grass clippings engine parts will retain most of the combustion heat Parts will expand probably distort and possibly seize There fore all finned surfaces should be cleaned regularly C HAPTER 1 3 Preventive Maintenance and Troubleshooting optical tachometer owner s manual prev
13. ailable online These manuals can often be accessed free of charge A service manual contains more detailed infor mation than the owner s manual Service manuals are often published for each engine type a manu facturer produces For example one manufacturer publishes a manual for all variations of the single cylinder engines it produces and another manual for all two cylinder engines it makes Some com panies publish service manuals for engines from a variety of manufacturers Service manuals can generally be purchased directly from engine manufacturers as well as from aftermarket publishers Often you can pur chase service manuals at shops that sell engines and engine parts Service manuals generally include comprehen sive service procedures detailed drawings of vari ous engine assemblies and troubleshooting charts Section 4 Engine Service as well as a variety of tolerances clearances and specifications needed to properly troubleshoot and service a specific engine The service procedures found in most manuals list the steps to take in order to accomplish a task effectively The detailed drawings of assemblies and systems are often exploded views that can help you disassemble and reassemble parts in the right order Troubleshooting charts list the most common engine troubles along with possible causes and suggested remedies See Figure 13 31 Engine specifications tolerances and clear ances are also given i
14. an engine provide valuable information This sticker displays the engine s build date and serial number This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved Summary Preventive maintenance involves tasks that must be performed regularly to keep an engine working properly Cleaning a small air cooled engine periodically can help prevent overheating For proper cooling action air must pass across the metal surfaces of the cylinder block and cyl inder head If the cooling fins are insulated by dirt leaves and or grass clippings engine parts will retain most of the combustion heat Parts will expand probably distort and possibly seize Crankcase oil in four cycle engines should be checked periodically The small engine manu facturer will recommend oil changes at intervals based on hours of running time The time speci fied may vary from 10 50 hours Engine cables and linkage should be lubricated periodically to ensure smooth operation and re duce the chances of binding and premature wear Many manufacturers recommend silicone based lubricants for use on cables and linkages Unlike petroleum based products these lubricants will not attract dirt after they are applied The spark plug should periodically be removed for inspection and cleaned or replaced Carefully examine the electrode end of the plug An insula tor or electrodes that are wet with fuel or
15. and sludge collects in the crankcase Changing Oil Changing engine oil is not difficult Begin by running the engine until it is thoroughly warmed up Warm oil will drain more completely and more contaminants will be removed if the oil is agitated Turn off the engine and disconnect the spark plug The oil drain plug is located at a low point on the crankcase usually along the outside edge of the base See Figure 13 4 Drain plug Figure 13 4 The oil drain plug is located at a low point in the crankcase to permit oil to drain completely Some engines do not have an oil drain plug Oil must be drained through the filler hole on these engines Clean the dirt from the drain plug area and then remove the plug with a proper wrench Figure 13 5 Allow the oil to drain for approxi mately five minutes to remove as much contami nated oil as possible See Figure 13 6 If the drain hole is located on the side or top of the engine tilt the engine toward the drain hole if possible When draining is complete replace the drain plug Socket Figure 13 5 This technician is using a socket and ratchet to remove the drain plug The plug should be turned counterclockwise for removal Drain plug Figure 13 6 It may take several minutes for all the old oil to drain from the engine This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved
16. bri cated periodically to ensure smooth operation and reduce the chances of binding and premature wear Linkage throttle linkage governor linkage etc can generally be lubricated by spraying it with an appropriate lubricant Many manufacturers recommend silicone based lubricants for use on cables and linkages Unlike troleum based products these lubricants will not attract dirt after they are applied To lubricate cables throttle cable engine bale etc place a few drops of the recommended lubri cant between the cable and its housing at the high est end of the cable Allow the lubricant to run down between the cable and housing Lubricant should flow out of the low end of the cable If it does not add a few more drops of lubricant and allow it to run down the cable Continue this process until clean lubricant flows from the bottom end of the cable If desired spray lubricant can be used to lubri cate the cable Simply spray the lube between the cable and the housing and watch for it to exit at the low end of the cable See Figure 13 9 Some manufacturers produce a tool that pro vides a leak proof connection between the tube from a can of spray lubricant and the cable When this tool is used the lubricant is forced under pres sure through the cable making lubricating cables fast and easy This type of tool is especially help ful when lubricating cables that run horizontally rather than vertically Cha
17. cient cooling and proper compression A cylinder compression test can be a first step toward determining the condition of the upper major mechanical parts of the engine This test is especially valuable if an engine lacks power runs poorly and shows little or no improvement after fuel system and ignition adjustments A differen tial pressure test checks the condition of an engine by measuring leakage from the cylinder to other parts of the engine This test device and procedure can identify a specific worn or damaged compo nent in the engine that may or may not be directly related to the cylinder condition or rings Chapter 13 Preventive Maintenance and Troubleshooting Before starting any maintenance troubleshoot ing or service procedures the appropriate service information should be consulted Basic mainte nance and service information can often be found in the owner s manual A service manual contains more detailed information than the owner s man ual In addition to having the correct service infor mation it is important to identify the exact model engine you are servicing This will allow you to locate the proper specifications for the engine It will also help ensure that you order the correct re pair parts Review Questions E See Answer the following questions on a separate sheet of paper 1 True or False Preventive maintenance helps protect against premature engine wear 2 Keeping an engine c
18. date of engine manu facture the location of the assembly plant the engine warranty emissions control compliance etc Information on interpreting model numbers as well as other engine identification numbers can be found in an appropriate service manual Chapter 13 Preventive Maintenance and Troubleshooting Engine Troubleshooting Chart Cause Engine fails to start o Remedy r starts with difficulty No fuel in tank Shut off valve closed Obstructed fuel line Fill tank with clean fresh fuel Open valve Clean fuel screen and line If necessary remove and clean carburetor Tank cap vent obstructed Water in fuel Open vent in fuel tank cap Drain tank Clean carburetor and fuel lines Dry spark plug and points Fill tank with clean fresh fuel Engine overchoked Improper carburetor adjustment Close fuel shut off and pull starter until engine starts Reopen fuel shut off for normal fuel flow Adjust carburetor Loose or defective magneto wiring Faulty magneto Check magneto wiring for shorts or grounds repair if necessary Check timing point gap if necessary overhaul magneto Spark plug fouled Spark plug porcelain cracked Poor compression No spark at plug Clean and re gap spark plug Replace spark plug Overhaul engine Disconnect ignition cut off wire at the engine Crank engine If spark at spark plug ignition switch or safety switch interlock swi
19. e that may or may not be directly related to the cylinder condi tion or rings The device is designed so that spe cific leakages can be detected and isolated before disassembling parts of the engine The differential pressure tester requires the application of air pressure to the cylinder being tested with the piston at top dead center on the compression stroke A schematic diagram of the differential pres sure tester is shown in Figure 13 29 As the reg 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 valve is opened and leakage through the cylinder increases the cylinder pressure gauge will record a proportionally lower reading The differential pressure test can be applied to single cylinder engines or multiple cylinder engines Each cylinder is tested separately and in the same manner Use the following procedure to test 1 Run engine until it is warmed up to provide uniform lubrication to cylinder walls and rings 2 Remove the spark plug wire s and spark plug s Regulated Air shutoff pressure gauge valve Cylinder P pressure gauge Piston at top dead center To air Metering compressor orifice Figure 13 29 This schematic diagram shows a differential pressure tester connected to an engine cylinder Eastern Technology Corp 3 Rotate the engine crankshaft until the piston of the cylinder being te
20. eet and at an angle of 45 These tachom eters are small enough to fit in a pocket and weigh only 6 ounces This is a safe method of measur ing engine rpm because contact with a hot engine is not necessary and a safe distance from moving parts can be maintained Digital tachometer Lead to spark plug wire Figure 13 26 A digital tachometer can be used to check engine rpm This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved Figure 13 27 This optical tachometer can measure rpm without contacting the engine by aiming it at a rotating part that has a reflective tape attached Monarch Instrument Testing Compression A cylinder compression test can be a first step toward determining the condition of the upper major mechanical parts of the engine This test is especially valuable if an engine lacks power runs poorly and shows little or no improvement after fuel system and ignition adjustments To perform a compression test Run the engine until it is warm Disconnect all drives to the engine Open the choke and throttle valves wide Remove the air cleaner Remove the spark plug and insert the compression gauge See Figure 13 28 6 Crank the engine as fast as possible and read the gauge Repeat the test to ensure accuracy OF WN FH Engines equipped with compression release camshafts may have to be cranked in reverse rota
21. entive maintenance tial pressure test reverse flushing tachometer service manual plug systematic troubleshooting thread chaser Methods for cleaning small air cooled engines vary Begin by removing any shrouds or engine covers obstructing the cooling fins You can then blow debris from the fins with compressed air and use a cleaning solvent to remove any remaining dirt and oil See Figure 13 1 Alternately you can scrape the dirty areas with a piece of wood and wipe them with a clean cloth Various multipurpose spray cleaners are suitable for use on small engines When using compressed air be extremely careful where you direct the blast of air Wear safety goggles Never direct the air blast toward skin or clothing In addition to cleaning cooling fins be sure to clean the engine crankcase area This area also trans fers a great deal of engine heat to the surrounding air A coating of dirt or oil will insulate the crankcase and may contribute to engine overheating 243 This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved Figure 13 1 This chain saw engine is being cleaned with compressed air Checking Oil Level and Condition Crankcase oil in four cycle engines should be checked periodically Preferably it should be checked each time fuel is added The engine manufacturer provides a means of visually inspecting the level and condition
22. er After washing the element wrap it in dry cloth and squeeze it dry Absorbent toweling works well for this procedure Section 4 Engine Service Air cleaner cover Figure 13 12 The cover on this air cleaner housing is held in place by a screw Oil wetted air cleaner Figure 13 13 After the cover is removed the element can be pulled from the receptacle The plastic foam should be saturated with clean engine oil After saturating the element squeeze excess oil out of the foam See Figure 13 14 Finally reassemble the air filter unit Follow any special instructions found in the owner s manual for the specific engine and filter Most dry type air filter elements pleated paper are designed to be thrown away when they become dirty Nevertheless you can clean a pleated paper filter element by tapping it on a flat surface to dislodge light accumulations of dirt However if the element will not tap clean it must be replaced Chapter 13 Preventive Maintenance and Troubleshooting C D Figure13 14 The sequence for servicing a foam type filter element is shown A Wash the foam element thoroughly in liquid detergent and water B Wrap the foam in cloth and squeeze it dry C Saturate the foam with clean oil D Squeeze out the excess oil compressed air to clean the paper filter the air can damage the filter element The Iter may not prevent fine dirt from entering When installing a
23. gged Open vent hole Governor parts sticking or binding Clean and if necessary repair governor parts Carburetor throttle linkage or throttle shaft and or butterfly binding or sticking Clean lubricate or adjust linkage and deburr throttle shaft or butterfly Intermittent spark or spark plug Disconnect ignition cut off wire at the engine Crank engine If spark check ignition switch safety switch and interlock switch If no spark check magneto Check wires for poor connections cuts or breaks Improper carburetor adjustment Adjust carburetor Dirty carburetor Clean carburetor Engine vibrates excessively Engine not securely mounted Bent crankshaft Associated equipment out of balance Tighten loose mounting bolts Replace crankshaft Check associated equipment Figure 13 31 Continued Chapter 13 Preventive Maintenance and Troubleshooting Engine Troubleshooting Chart Cause Remedy Engine uses excessive amount of oil four cycle only Engine speed too fast Using tachometer adjust engine RPM to specifications Oil level too high To check level turn dipstick cap tightly into receptacle for accurate level reading Drain excess oil as needed Oil filler cap loose or gasket damaged causing spillage out of breather Replace ring gasket under cap and tighten cap securely Breather mechanism damaged or dirty causing leakage Drain ho
24. illcox Co Inc All rights reserved Section 4 Engine Service Engine Troubleshooting C hart Cause Remedy Engine lacks power Choke partially closed Improper carburetor adjustment Magneto improperly timed Worn rings or piston Air cleaner fouled Lack of lubrication four cycle only Open choke Adjust carburetor Time magneto Replace rings or piston Clean air cleaner Fill crankcase to the proper level Valves leaking four cycle only Grind valves and set to recommended specifications Reed fouled or sluggish two cycle Clean or replace reed Improper amount of oil in fuel mixture two cycle only Drain tank fill with correct mixture Crankcase seals leak two cycle only Replace worn crankcase seals Engine overheats Engine improperly timed Carburetor improperly adjusted Airflow obstructed Cooling fins clogged Excessive load on the engine Carbon in combustion chamber Lack of lubrication four cycle only Improper amount of oil in fuel mixture two cycle only Time engine Adjust carburetor Remove any obstructions from air passages in shrouds Clean cooling fins Check operation of associated equipment reduce excessive load Remove cylinder head and clean carbon from head and piston Fill crankcase to proper level Drain tank fill with correct mixture Engine surges or runs unevenly Fuel tank cap vent hole clo
25. intake valve a hissing in the exhaust suggests a leaking exhaust valve and hissing from the crankcase breather indicates leaking piston rings See Figure 13 30 If the test indicates a valve problem first check valve clearance to make sure the valve is not being held open due to inadequate clearance This sample chapter is for review purposes only Copyright The Goodheart Willcox Co Inc All rights reserved Air Escaping from Indication defective intake valve carburetor intake exhaust system defective exhaust valve crankcase breather defective piston rings Figure 13 30 The chart shows the location of air leaks and the indicated defects Service Information Before starting any maintenance trouble shooting or service procedures the appropriate service information should be consulted Basic maintenance and service information can often be found in the owner s manual provided with the implement or the engine itself The owner s man ual typically includes information on maintenance schedules fluid capacities and part numbers for maintenance components filters spark plugs etc It may also include very basic maintenance and troubleshooting procedures For example the owner s manual may include instructions for changing an engine air filter or diagnosing a no start condition Many engine and implement manufacturers make copies of their owner s manual av
26. lant The number of balls that float indicates the strength of the coolant Some hydrometers have a pointer that indicates coolant strength on a scale printed on the body of the tester Maintaining Outboard Cooling Systems Outboard engine cooling systems can be clogged with dirt sand or other debris Flush ing the internal cooling system of an outboard engine is extremely important Flushing is done by attaching a freshwater hose to the water scoop or by operating the engine in a barrel of freshwater for several minutes Chapter 13 Preventive Maintenance and Troubleshooting Figure 13 23 Coolant strength can be checked with a hydrometer Engines operated in saltwater are exposed to extremely corrosive conditions Exposed engine parts require careful maintenance Flush the cool ing system with fresh water after each use Rinse the engine with freshwater and wipe all lower unit parts with a clean oily cloth Ignition leads and spark plug insulators should also be wiped fre quently to prevent an accumulation of salt residue Outboard engines used in saltwater should be removed from the water immediately after operation If the engine cannot be removed tilt the gearcase out of the water and rinse it with freshwater The gearcase must be removed from the water when not in use Storing an Engine Several precautions should be taken when stor ing an air cooled engine for an extended period such as when storing an i
27. le in breather box clogged causing oil to spill out of breather Gaskets damaged or gasket surfaces nicked causing oil to leak out Valve guides worn excessively thus passing oil into combustion chamber Cylinder wall worn or glazed allowing oil to bypass rings into combustion chamber Piston rings and grooves worn excessively Piston fit undersized Piston oil control ring return holes clogged Oil passages obstructed Figure 13 31 Tolerances and Clearances for the J 321 Engine Cylinder bore Max 2126051 Min 2 1260 Piston skirt diameter Max 2 1227 Min 2 1220 Piston ring width Max 0935 Min 0925 Piston pin diameter Max 5001 Min 4999 Spark plug gap 0307 Piston skirt to cylinder Max 0045 clearance Min 0033 Figure 13 32 Typical tolerance and clearance chart Jacobsen Mfg Co Replace breather assembly Clean hole with wire to allow oil to return to crankcase Clean and smooth gasket surfaces Always use new gaskets Ream valve guide oversize and install 1 32 oversize valve Bore hone or deglaze cylinder as necessary Reinstall new rings check land clearance and correct as necessary Measure and replace piston as necessary Remove oil control ring and clean return holes Clean out all oil passages z ms ed ni r Paia ite rt he Wi 05 ore Briggs Siajn oy Il F BUILD D4 Figure 13 33 Identification numbers found on
28. lean area When removing the engine from storage fill the crankcase with the recommended type and amount of fresh oil four stroke engine Then remove the spark plug and use the pull rope or starter to spin the engine rapidly to remove excess oil from the cyl inder Clean or replace the spark plug Then clean and oil the air filter or replace cartridge if necessary Figure 13 24 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 If necessary fill the fuel tank If you are servic ing a two stroke engine make sure the proper fuel oil mixture is added to the tank See Chapter 11 for additional information on mixing oil and fuel Start the engine and let it idle until warm Adjust the idle speed if necessary Increase the engine speed in the normal manner Make a brief test run while listening to the engine and watch ing the condition of all parts Storing Liquid Cooled Engines In addition to the storage precautions cov ered previously storing liquid cooled engines for lengthy periods particularly during winter calls for special maintenance procedures If the engine has a pressurized system the coolant must be strong enough to protect against freezing at the lowest possible temperatures If the engine will not be started at any time dur ing storage drain the cooling system complete
29. lean can help prevent 3 True or False Never run an engine if the oil level is above full mark 4 Although oil does not wear out excess make the oil useless 5 When changing oil the engine should be A cold B warm C running D None of the above 6 Many manufacturers recommend using based lubricants on cables and linkages 7 True or False Most manufacturers recommend replacing a carbon fouled spark plug 8 Name three problems caused by a plugged air filter 9 Why should you refrain from using compressed air to clean a pleated paper air filter element 10 What two problems can be caused by a clogged muffler 11 True or False All mufflers can be cleaned by soaking them in solvent 12 When storing an engine for an extended period should be added to the gasoline to prevent fuel breakdown and the buildup of gum varnish and corrosion 13 To prevent the formation of rust and scale antifreeze containing a rust should be used in the cooling system 14 Outboard engines operated in saltwater are exposed to conditions 15 When storing outboard engines all plugs should be removed from the and housing 16 Systematic troubleshooting involves looking for the possible problem first 17 In order to run properly an engine must have proper carburetion correct ignition system operation adequate lubrication sufficient cooling and 18 True or False A compression
30. located over the valve stem chamber It is held in place with two or more screws To inspect the breather remove the screws and 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 ir aa heres EA Be 2S Figure 13 17 The foam pre cleaner can be washed in detergent and water and squeezed dry valve similar to the one shown in Figure 13 18 The valve allows outward airflow only Inspect the valve to make sure it is not dam aged or distorted If it is the breather assembly must be replaced If applicable see that the drain hole in the body of the assembly is open This hole permits accumulated oil to return to engine After all components have been inspected replace dam aged gaskets reinstall the assembly on the engine and tighten the screws Muffler Service Anengine takes in large quantities of air mixed with fuel and then burns the mixture Unless the engine readily rids itself of the by products of combustion its efficiency will be greatly reduced Valve Drain hole Figure 13 18 Crankcase breather elements need periodic inspection The function of the reed valve is to allow air to leave the crankcase but prevent it from entering Section 4 Engine Service This is the task of the exhaust system which in small gasoline engines mainly consists of exhaust port s and a small m
31. ly Then tag the engine to indicate its drained condition When storing outboard engines remove all plugs from the gearcase and drive shaft housing This allows accumulated water in the gearcase and cooling system to drain off Failure to take this precaution when winteriz ing may result in a cracked cylinder block and or gearcase plus possible damage to water channels and tubes Rock the engine from side to side to make certain all water has drained Refill the gearcase with the type of lubricant specified by the engine manufacturer Attend to all other lubrication rec ommendations made by the manufacturer for care of the engine being stored Systematic Troubleshooting Most small engine service and repair jobs can be done without taking the entire engine apart If the engine will not start is hard to start runs rough or lacks power troubleshooting may be necessary Troubleshooting is simply a number of tests and steps you go through to find a problem Sometimes the cause of an engine problem is easy to find At other times checking probable causes requires a certain amount of reasoning and the use of the process of elimination Also more than one fault can exist at the same time making it harder to locate the trouble Section 4 Engine Service Always take a systematic approach when trouble shooting small engines Systematic troubleshooting involves checking and or testing one component after another component until the
32. mplement for the win ter season Proper storage procedures will help ensure long engine life and easy starting the fol lowing season Begin by thoroughly cleaning the engine Layers of dirt and debris tend to hold moisture encouraging the formation of rust and corrosion Add fuel stabilizer to the fuel remaining in the tank and fill the tank with fresh gasoline See Figure 13 24 Fuel stabilizer will help prevent fuel breakdown and the formation of gum varnish and corrosion in the fuel system Start the engine and let it run for a few minutes so stabilized fuel flows through all parts of the fuel system If fuel stabilizer is not available run the engine dry of fuel Next drain the oil from the crankcase Do not refill it now Place a tag on the engine that says No Oil Rotate the engine so the piston is at bottom of the cylinder Remove the spark plug and squirt about one tablespoon of clean motor oil through the spark plug hole with an oil can Rotate the engine slowly several times to distribute the oil on the cylinder walls Then replace the spark plug With the spark plug wire disconnected use the pull rope to rotate the engine slowly until compres sion resistance is felt Then rotate the engine an additional one quarter turn to close off its ports This seals the cylinder and prevents moisture entry If possible make sure the throttle is in the off position and the choke is closed Then store the engine in a dry c
33. n a service manual See Figure 13 32 When tolerance specifications show two values the actual dimension must be some where between the two values In Figure 13 32 for example the cylinder bore diameter must mea sure somewhere between 2 1260 and 2 1265 Engine Identification In addition to having the correct service infor mation it is important to identify the exact model engine you are servicing This will allow you to locate the proper specifications for the engine It will also help ensure that you order the correct repair parts Most engines have a model number displayed on a Sticker affixed to the engine housing or to the engine itself On some engines the model number is stamped into the engine block the metal shroud or some other engine component The model num ber will provide you with specific information about the engine at hand For example it will gen erally provide you with information on crankshaft orientation vertical or horizontal starter type recoil start or electric start carburetor type etc In addition to the model number some manu facturers use ID numbers serial numbers or other code numbers that convey additional information See Figure 13 33 These numbers may identify unique features of the engine For example the engine used ona certain model of lawnmower may have a crankshaft with a special snout to accom modate the mower s blade The numbers may also provide information on the
34. of the oil Use the type and viscosity grade of oil recommended by the manufacturer and main tain it at the proper operating level To check the oil level in engines equipped with a dipstick withdraw the dipstick and wipe it dry Reinsert the dipstick as far as it will go Withdraw it a second time and observe the oil level on the dipstick See Figure 13 2 The markings on dipsticks may vary but all will have a Low Add mark and a Full mark Add oil if the level is at or below the Low mark Do not run the engine with oil showing above the Full mark on the dipstick If the crankcase oil level is high drain some oil ling the crankcase with oil can foul plugs and ie engine to use too much oil Some small gasoline engines do not have dip sticks Instead they have a filler plug that threads into the filler hole to seal out dirt and seal in the oil Figure 13 3 shows the proper method of loosening one type of filler plug When the plug is removed the oil level should be at the top of the filler hole or to a mark just inside the filler hole Section 4 Engine Service i pide Figure 13 2 Checking the oil is an important part of preventive maintenance a e Ta J E ha Plug Figure 13 3 A screwdriver can be used to remove the type of oil filler plug shown here If the engine oil level drops at an excessive rate requires the addition of oil frequently look for the cause Refer
35. pleated paper type air fil ter element the pleated paper should face the external side of the air cleaner receptacle See Figure 13 15 Engines designed to be used in dusty conditions may have dual element air cleaners Dual element air cleaners use a plastic foam filter pre cleaner that is mounted over a pleated paper filter element See Figure 13 16 When servicing this type of fil ter the pre cleaner can be washed in detergent and water and squeezed dry Figure 13 17 Some pre cleaners must be oiled after they are cleaned The paper filter element should be cleaned by shaking or replaced Every engine to be serviced or repaired should have its air cleaner examined If the air cleaner ele ment or cartridge is damaged or shows signs of restriction replace it Worn or damaged mounting gaskets and air cleaner gaskets should be replaced to prevent dirt and dust from entering the engine through an improper seal around the filter Air cleaner receptacle Cover Filter element Figure 13 15 The pleated paper should face the outside of the air cleaner receptacle away from the engine Pleated paper filter Pre cleaner Figure 13 16 In a dual element air cleaner the pre cleaner must be removed before the pleated paper filter can be serviced Crankcase Breather Service If the small gasoline engine has a crankcase breather the breather assembly should be removed and cleaned periodically The breather is
36. pter 13 Preventive Maintenance and Troubleshooting Cable Housing Figure 13 9 Lubricant can be sprayed between the cable and the housing Spark Plug Service The spark plug should periodically be removed for inspection and cleaned or replaced Begin by using compressed air to blow dirt away from the base of the spark plug Remove the spark plug wire from the plug by pulling on the wire s insulating boot only Do not pull on the wire itself See Figure 13 10 Install a deep spark plug socket on the plug and carefully turn the ratchet handle counter clockwise Unscrew the spark plug and remove it from the cylinder head Carefully examine the electrode end of the plug The electrodes and ceramic insulator should be dry An insulator or electrodes that are wet with fuel or oil may be a sign of serious engine prob lems A dry insulator that has a beige or gray tan color indicates that the engine is in good condition Next examine the electrodes for any erosion burn ing or carbon fouling Refer to Spark Plug Condition chart in the Appendix of this text If the spark plug insulator and electrodes appear to be good no evidence of fouling or wear the plug can be reinstalled If not install a new plug of the correct type Refer to the manu facturer s technical service manuals for the proper replacement spark plug Check the electrode gap with a wire type feeler gauge Figure 13 11 The engine service manual Spark plug
37. r to wash the cable connectors and battery terminals One teaspoon of baking soda to one cup of water 3 Use a stiff brush to remove the corrosion from the cable connectors and battery terminals Figure 13 21 Corroded terminal r Figure 13 20 This battery terminal and cable connection is extremely corroded Tn Figure 13 21 A parts brush old toothbrush or other stiff bristle brush should be used to remove the corrosion from the cable connectors and battery terminals 4 Rinse the battery and connectors with clear water and dry the battery case and terminals with absorbent cloths Figure 13 22 5 Coat the terminals with a waterproof dielectric grease to prevent further corrosion 6 Reinstall the battery cables on the battery terminals In negative ground systems the positive cable should be connected before the negative cable Charge a battery only when it needs it Nor mally the alternator driven by the engine keeps the battery charged If the battery is old and does not crank the engine it should be tested and pos 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 Figure 13 22 After cleaning rinse the battery terminals and cable connectors with clear water is low on fluid will not take a full charge This battery will eventually overheat the plates
38. sted is at top dead center of the compression stroke Both valves must be closed 4 Install the holding fixture supplied with the tester to prevent the crankshaft from turning during the test 5 Thread the adaptor into the spark plug hole 6 Connect the adaptor on the rubber hose to the quick disconnect fitting on the tester 7 Connect an air source of at least 90 psi to the tester adaptor Make sure all personnel and objects are clear of the engine shaft belts pulleys or other devices connected to the engine shaft 8 Slowly adjust the regulated pressure gauge on the left with the regulator knob to read 80 psi 9 The right hand gauge indicates the relative pressure of the cylinder being tested Due to standard engine clearances and normal wear no cylinder is expected to maintain a perfect 80 psi Generally a reading of 60 psi or above is acceptable It is important that all cylinders on multi cylinder engines have a somewhat consistent reading Good judgment should be used as to the allowable tolerance between cylinders Recheck a cylinder that has a reading that is significantly lower 15 psi or more than the other cylinder s If a second reading is still low the cylinder should be suspected of being defective 10 By listening for the sound of escaping air you can determine leakage points in the engine and the cause of the low pressure reading A hissing at the carburetor intake indicates a leaking
39. tch is inoperative If no spark check magneto Crankcase seals and or gaskets leaking two cycle only Exhaust ports plugged two cycle only Replace seals and or gaskets Clean exhaust ports Engine Carbon in combustion chamber Loose or worn connecting rod Loose flywheel Worn cylinder knocks Remove cylinder head and clean carbon from head and piston Replace connecting rod Check flywheel key and keyway replace parts if necessary Tighten flywheel nut to proper torque Replace cylinder Improper magneto timing Time magneto Engine misses under load Spark plug fouled Spark plug porcelain cracked Clean and regap spark plug Replace spark plug Improper spark plug gap Pitted magneto breaker points Re gap spark plug Replace pitted breaker points Magneto breaker arm sluggish Faulty condenser Clean and lubricate breaker point arm Check condenser on a tester replace if defective Improper carburetor adjustment Improper valve clearance Weak valve spring Reed fouled or sluggish two cycle only Crankcase seals leak two cycle only Typical troubleshooting chart for small gas engines Adjust carburetor Adjust valve clearance to recommended specifications Replace valve spring Clean or replace reed Replace worn crankcase seals Figure 13 31 Continued This sample chapter is for review purposes only Copyright The Goodheart W
40. tion to obtain an accurate reading Section 4 Engine Service Figure 13 28 A compression test can indicate the condition of various mechanical components of an engine An engine producing a compression less than the minimum specified by the manufacturer usu ally has one or more of the following problems e Leaking cylinder head gasket e Warped cylinder head e Worn piston rings e Worn cylinder bore Damaged piston Burned or warped valves e Improper valve clearance e Broken or weak valve springs To determine whether the valves or rings are at fault pour a tablespoonful of SAE 30 oil into the spark plug hole Crank the engine several times to spread the oil and repeat the compression test The heavy oil will temporarily seal leakage at the rings If the compression does not improve the leakage is due to problems with the valves cylinder head or piston This does not disprove a problem with the rings the engine may have worn rings in addi tion to its other problems On the other hand if the compression is much higher than the original test the leakage is due solely to defective piston rings Chapter 13 Preventive Maintenance and Troubleshooting Testing Differential Pressure A differential pressure test checks the con dition of an engine by measuring leakage from the cylinder to other parts of the engine This test device and procedure can identify a specific worn or damaged component in the engin
41. to a troubleshooting chart for the particular engine at hand Troubleshooting charts are covered later in this chapter Typical causes of excess oil consumption are external leaks worn oil seals around the crankshaft worn valve guides worn piston rings or a hot running engine The color of used oil is not always an accurate indi cation of its condition Additives in the oil may change its color without decreasing its lubricating qualities Chapter 13 Preventive Maintenance and Troubleshooting The small engine manufacturer will recommend oil changes at intervals based on hours of running time A new engine should have the first oil drained 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 Engine oil does not wear out It always remains slippery However oil used for many hours of engine operation becomes contaminated with dirt particles soot sludge varnish forming materials metal par ticles water corrosive acids and gasoline These con taminants eventually render the oil useless The harm they cause outweighs the lubricating quality of the oil The time interval for oil changes is selected so that the oil never reaches a loaded level of contami nation Loaded oil cannot absorb any more con taminants and still be an effective lubricant When oil reaches a loaded condition varnish deposits begin to form on the piston and rings
42. uel system is being serviced care must be taken to minimize spillage glennebo Shutterstock
43. uffler A muffler is designed to reduce noise and allow exhaust gases to escape When it becomes clogged with carbon soot gases cannot get out of the combustion chamber quickly enough to allow fresh air and fuel to enter This causes a loss in engine power along with a tendency to overheat If clogging is suspected with a sealed muffler install a new muffler and check for improved engine efficiency See Figure 13 19 If a muffler is designed to be taken apart it can be disassembled and cleaned in a solvent to remove soot and other debris Locking tab 4 Figure 13 19 Locking tabs are often used to prevent muffler fasteners from loosening A Before attempting to remove the fasteners use a screwdriver to bend the tabs out of the way B Once tabs are bent down a wrench can be used to remove the fasteners securing the muffler to the engine Chapter 13 Preventive Maintenance and Troubleshooting Battery Service The battery in a small engine powered imple ment may be either a maintenance free battery or a conventional lead acid battery Check the manu facturer s service information to determine which type is being used The maintenance free battery should not be replaced with a conventional lead acid battery The electrical system is designed exclusively for a maintenance free battery and the electrical system will not work properly with a conventional lead acid battery Conventional lead acid batteries need occa
44. y Corrosion at the battery terminals and cable con nectors is not uncommon The corrosion should be cleaned from the terminals The pressurized liquid cooling systems used in small engines require maintenance similar to that employed in the automobile engine Because the combination of water and metal sometimes produces harmful chemical reactions that attack the water jacket antifreeze containing a chemical rust inhibitor should be added whenever a system is drained and refilled Outboard engine cooling systems can be clogged with dirt sand or other debris Flushing the internal cooling system of an outboard engine is extremely important Several precautions should be taken when storing an air cooled engine Proper storage pro cedures will help ensure long engine life and easy starting the following season Storing liquid cooled engines for lengthy periods calls for special maintenance procedures If the engine has a pres surized system the coolant must be strong enough to protect against freezing at the lowest possible temperatures If the engine will not start is hard to start runs rough or lacks power troubleshooting may be necessary Troubleshooting is simply a number of tests and steps you go through to find a problem In order to start and run properly an engine must meet five fundamental operating requirements These requirements include proper carburetion correct ignition system operation adequate lubri cation suffi
Download Pdf Manuals
Related Search