1 Objectives To understand the importance of servicing

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Objectives • To understand the importance of servicing engine systems. • To acquire knowledge on various maintenance procedures. • To understand troubleshooting procedures. • To understand common reasons for engine malfunction. 2 2

Main Menu Engine Maintenance Troubleshooting 3 3

ENGINE MAINTENANCE 4 4

Engine Maintenance • Is important in order to keep problems and breakdowns from occurring • Should be completed on a regular basis – setting up a maintenance schedule can ensure manufacturer’s maintenance requirements are met • this can also help establish an equipment record-keeping system • a schedule should be formulated with the manufacturer’s suggested intervals found in the owner’s manual 5

Engine Maintenance • May include: – cleaning engine components – using the correct spark plugs – servicing the carburetor – servicing the electronic fuel injection – preparing the engine for storage – servicing emission control parts – verifying fuel tank and fuel line permeation 6

Cleaning Engine Components • Is the most important type of maintenance for an air-cooled engine – this is particularly important for today’s lowemission engines, which operate at a higher engine temperature • Includes: – cleaning cylinder cooling fins – changing fuel filters – servicing air filters 7

Cleaning Cylinder Cooling Fins • Is important in order to properly maintain the transfer of heat – the fins around the engine and on the cylinder head act as a heat transfer medium • the heat which is generated by combustion travels through the fins to the atmosphere – an accumulation of dirt or debris on the fins acts as an insulator which blocks the transfer of heat 8

Cleaning Cylinder Cooling Fins • Keeps the engine from overheating – excessive heat can cause: • thermal decomposition from the extreme pressure • anti-wear additives in the oil which results in reduced wear protection • increased engine deposits • pre-ignition Four-Stroke Fact: Excessive heat can also enlarge the size of the piston, which reduces the space between the piston and cylinder wall. This condition will result in a breakdown of the boundary lubrication and permit metal-to-metal contact, causing wear, scuffing or piston-to -cylinder seizure. 9

Changing Fuel Filters • Should be completed on a regular basis – a completely blocked fuel filter will stop the engine – a partially blocked filter can cause the mixture to be lean • which is a major cause of piston seizure/scuffing and overheating failure 10

Servicing Air Filters • Is completed by keeping the filter clean and dry – dirty or punctured air filters permit the entry of dust and excess moisture into the engine – debris can enter when the filter is not perforated, but simply dirty 11

Servicing Air Filters • Keeps the engine running smoothly – abrasive particles create internal wear and contribute to piston rings sticking and scored cylinders – a blocked air filter causes an externally vented carburetor engine to run rich, with too much gas and too little air • this will create high quantitates of carbon in the combustion chamber • this condition also leads to fouled spark plugs, blocked spark arrestors, loss of engine power and engine damage 12

Servicing Air Filters • Should be completed by using hot soapy water, followed by a thorough rinse of all soap residue before drying • May include oiling foam filters – check with the engine manufacturer to determine if the unit being serviced requires this and, if so, what type of oil should be applied Four-Stroke Fact: It is not recommended to wash or clean foam filters in gasoline. 13

Using the Correct Spark Plug • Is accomplished by following the recommendations in the owner’s manual or parts breakdown – the spark plug’s electrode area typically operates between 700 degrees Fahrenheit and 1500 degrees Fahrenheit • less than 700 degrees Fahrenheit will cause a buildup of carbon which will short or foul the spark plug and will eventually stop the engine • around 1500 degrees Fahrenheit, the spark plug venter electrode will begin to glow, causing the combustion mixture to ignite before the spark occurs (pre-ignition) 14

Using the Correct Spark Plug • Includes utilizing a spark plug which maintains an ideal self-cleaning temperature – if the temperature is too low, carbon buildup on the insulator nose will occur, causing the plug to misfire – a “cold” spark plug readily dissipates the spark plug’s insulator nose heat • a “hot” spark plug dissipates the spark plug’s insulator nose heat at a slower rate 15

Servicing Carburetors • Should be included in a regular maintenance schedule • Includes: – carburetor adjustments – rinsing and cleaning – initial inspection – inspection of fuel inlet screen – inspection of fuel bowl and float 16

Carburetor Adjustments • Vary per engine manufacturer – it is critical each carburetor is adjusted to the manufacturer’s procedures and specifications • this ensures the engine will comply with emission regulations and allow the engine to run at optimum power Four-Stroke Fact: No person should ever bypass EPA required adjustment restrictors. Any dealer who tampers with emissioncertified engines is liable for a penalty of up to $37, 500 per tampering act per engine. 17

Carburetor Adjustments • Are an important part of engine performance – carburetors adjusted too lean will have increased operating temperature and NOX (oxides of nitrogen) emissions – carburetors adjusted too rich will have increased levels of hydrocarbons (HC) and carbon monoxide (CO) in the exhaust and will not be emission compliant • this also causes overheating 18

Carburetor Adjustments • May not be completed on all engines – many small engines being produced today come equipped with non-adjustable carburetors • some small engines continue to use adjustable carburetors with low-speed and high-speed mixture needles covered with a limiter cap 19

Carburetor Limiter Caps • Prevent users from making adjustments to a carburetor which would cause it to be outside the emission regulations Limiter Cap 20

Carburetor Limiter Caps • Must be installed after overhaul and final adjustments to ensure the unit complies with CARB and EPA regulations Four-Stroke Fact: Any specialty tools used to remove limiter caps or adjustment tools are not to be sold to equipment end users, such as noncertified technicians, homeowners and commercial users. 21

Rinsing & Cleaning • Is completed by using an ultrasonic cleaner – which is the preferred method of cleaning carburetors and fuel system components • May also be completed by using an approved cleaning solvent • Is completed in the following manner: – after rinsing, blow low-pressure air through all the channels • drill bits, tag wire and other hard metal objects should never be used to clean away obstructions • a soft nylon line may be used to clean any orifices 22

Initial Inspection • Is completed in the following manner: 1. verify components are not missing or damaged 2. check the throttle and choke shafts to ensure they are not loose or worn; they should open and close freely • if loose or worn, the carburetor will need to be replaced 3. remove all excess debris Four-Stroke Fact: Never use a cloth to clean a carburetor. Tiny lint particles are likely to adhere to the components and cause malfunction. 23

Inspect the Fuel Inlet Screen • In order to keep the carburetor functioning properly • In order to verify the screen is not clogged – clogged screens will restrict fuel flow, affect acceleration and impair high-speed performance Four-Stroke Fact: The fuel inlet screens are located in the fuel tank at the ends of the pickup tubes and are calibrated to the carburetor model. These screens filter fuel before it enters the metering chamber. Typical screen colors are silver and brass. 24

Inspect the Fuel Bowl & Float • In order to keep the carburetor functioning efficiently – any components which appear damaged should be replaced • In order to detect deformation – particularly at the point of contact with the carburetor-to-fuel-bowl gasket • In the following manner: 1. remove the float hinge pin and check the float for damage and possible leakage 2. remove and inspect the float valve for debris or wear 25

Servicing the Electronic Fuel Injection (EFI) • Includes maintaining the tank, fuel pump, filter, throttle body and injector – because of the complex nature of these systems, there is very little maintenance to be done • May include: – adding manufacturer-recommended additives to the fuel – visually inspecting all components including wiring and connectors – keeping components free of debris 26

Preparing Engines for Storage • Is vital to keep the engine running smoothly – one season of bad storage can do more damage than several seasons of operation – damage from rust and corrosion, plugged carburetor passages and stale fuel can lead to problems the next time the engine is used • Includes preparing the fuel tank and fogging the engine 27

Preparing the Fuel Tank • Includes completely draining the fuel from the fuel tank and carburetor – during in-season use, fuel additives can be added to fuel to decrease the oxidation process • the additive is only effective if it is added to fresh fuel 28

Fogging the Engine • Is completed by coating the internal parts with oil to prevent any problems with corrosion or rust – this is especially true when using old spark plugs Four-Stroke Fact: When the engine is started the following season, it will smoke for a period of time until all the excess oil is removed. 29

Fogging the Engine • Is accomplished in the following manner: 1. removing the air cleaner and starting the engine 2. while the engine is operating at moderate speed, engine oil or fogging oil is squirted into the carburetor air inlet 3. oil is then introduced quickly to stall the engine • this will coat the intake system, cylinder, piston rings and exhaust system 30

Alternative to Fogging • Includes: 1. verify the spark plug wire is not installed on the spark plug 2. put a teaspoon of oil into the spark plug hole so the piston area is coated with lubrication • although this coats the cylinder and piston, fogging the engine provides more complete protection 3. pull the recoil starter slowly until the piston is at top dead center • this will ensure the combustion chamber is sealed by the piston to prevent any damage which may be caused by the environment during storage Four-Stroke Fact: The old spark plug should be replaced after the fogging and gapped to specification. 31

Servicing Emission Control Parts • Is important to the operation of the system – there are certain emission control parts which must be serviced with only genuine OEM parts or an acceptable equivalent, including: • • exhaust system carburetor ignition module flywheel • • spark plug fuel tank fuel feed line air filter Four-Stroke Fact: It is imperative for technicians to follow emission carburetor adjustments provided by the manufacturer and only install approved replacement parts. Failure to do so can result in degraded engine performance, engine seizure and an engine which will not meet EPA and CARB emission regulations. 32

Verifying Fuel Tank Permeation • Is important in order to control hydrocarbon vapor through tank walls – since 2007 (CARB Tier 3) and 2009 (EPA Phase 3), fuel tanks have been improved to limit these evaporative emissions • these low permeation tanks are either multilayer or fluorinated Four-Stroke Fact: Prior to regulation, fuel tanks would emit 11 grams of evaporative emissions per day. Regulated tanks can only emit 1. 5 grams per day. 33

Verifying Fuel Line & Fuel Cap Gasket Permeation • Is also important in order to limit emissions – since January 2012, all fuel feed lines (the line outside the fuel tank to the carburetor) and the fuel cap gasket must meet requirements • these regulations require manufacturers to update their fuel feed lines to new materials such as Viton and special rubber blends • technicians must make sure to install only the new material fuel lines on engines affected by this change Four-Stroke Fact: Pre-regulation fuel feed lines emitted 300 to 700 grams of hydrocarbons per day. Regulated lines emit only 15 grams per day. 34

Troubleshooting TROUBLESHOOTING 35 35

Troubleshooting • Is a systematic approach to solving problems dealing with engine performance – services are offered by equipment manufacturers and engine technicians • Should address specific issues • Begins with a systematic check 36

Systematic Checks • Are efficient, simple routines which are a logical approach to troubleshooting engine problems – after each step in the procedure, check the engine to determine whether the problem has been corrected • Are followed with systematic testing procedures to verify the assumption and arrive at a solution 37

Systematic Checks • Should cover four main areas – ignition – compression – fuel intake – exhaust 38

Ignition System Inspection • Is conducted by checking for spark with a tester which is able to load the ignition system – such as a three-point spark tester • May be completed on both running and non-running engines • Is accomplished in the following manner: 1. connect the tester in-line with the spark plug 2. turn the engine over and see if it will create a spark across a four mm gap at cranking speed 39

Ignition System Inspection 40

Failing Initial Ignition System Inspection • Is apparent when a spark is not present or is weak – isolate the on/off switch and disconnect it, then check for spark • if the engine still fails this test, additional checks of the module will need to be done prior to replacement, such as testing module ground resistance along with the primary and secondary leads 41

Passing Initial Ignition System Inspection • Should be followed with a second test – open the tester to a gap of six mm • if spark continues, this will ensure the ignition system is putting out adequate voltage to start and run the engine 42

Spark Plug Evaluation • Is part of the ignition inspection – using the correct heat range spark plug with today’s lean and hot running engines is more important than ever before • today’s power equipment engines must run leaner and hotter to meet stringent emission regulations Four-Stroke Fact: It is recommended to use only the spark plug called for in the manufacturer’s operator’s manual and service data. The spark plug manufacturer’s cross reference book should not be used. In most cases, this data is not current and could reference a spark plug which is two to three heat ranges colder or hotter than what is recommended. 43

Spark Plug Evaluation • Includes knowing the appearance of various issues – carbon-fouled spark plugs – overheated spark plugs – lean or hot running spark plugs 44

Carbon-Fouled Spark Plug Appearance • Heavy carbon buildup like this indicates a poorly running engine • Be sure to check compression and the intake system for leaks • The wrong heat range spark plug (cold or hot) can cause rapid carbon buildup 45

Overheated Spark Plug Appearance • The dull color outside of the spark plug and the flakes of carbon on the firing end are signs of very high engine operating temperatures • Carbon deposits can cause a short between the electrodes, preventing the arc which fires the fuel mixture which can occur from an incorrect (too hot) spark plug, blocked cooling fins or a partially plugged exhaust system 46

Overheated Spark Plugs • Must be corrected – it is likely the combustion chamber on this engine has the very same flaky deposits – a new plug may only work for a few minutes before another piece of carbon sticks between the electrodes again – pull the cylinder head and de-carbon both the piston and cylinder head before putting the engine back in service – do not forget to check the exhaust valve and muffler for carbon deposits 47

Lean or Hot Running Spark Plug Appearance • A spark plug with a white insulator and eroded electrode indicates the engine is running very lean and hot • Notice the glazed porcelain and the peppery specks on the insulator, which are signs of a plug which is badly overheated 48

Correctly Operating Engine Spark Plug Appearance • This tan-colored center electrode insulator is what can be expected from an engine operating at the proper temperature at the correct air/fuel ratio 49

Compression Tests • Are used to verify a low compression diagnosis – a special compression test adapter and gauge which can safely read above the maximum expected psi must be used • Are performed in the following manner: 1. 2. 3. 4. remove the spark plug block the throttle plate fully open install the gauge adapter into spark plug hole rotate the engine until the gauge stops increasing 50

Compression Tests • Are useful in checking for a difference of cylinder conditions in multi-cylinder engines • Ensure all psi ratings do not differ by more than 10 percent – a difference in compression between cylinders does not automatically mean there is a problem with piston rings or the cylinder bore • the problem may be automatic compression release or valve lash related 51

Wet Compression Tests • Should be performed if a dry compression test indicates low compression • Are performed by adding a small amount of oil to the cylinder and repeating the compression check • Should indicate higher compression than the dry compression check – because oil creates a better seal against the top of the piston rings and cylinder bore Four-Stroke Fact: The lower the difference in readings between the dry and wet checks, the better the condition of the rings and bores. 52

Cylinder Leakage Test • Is considered a more accurate way to test for excessive combustion area leaks when compared to a compression test – this is due to a majority of small engines being equipped with an automatic compression release (ACR) to ease starting • Is used to check for excessive pressure loss in the combustion area 53

Cylinder Leakage Test • Requires the following: – both intake and exhaust valves must be fully closed – a source for moisture-free compressed air must be available – the ACR is disengaged while testing – the pushrods are removed at bottom dead center to ensure no valves are open 54

Cylinder Leakage Test • Is performed in the following manner: 1. run the engine long enough to reach operating temperature 2. remove the spark plug of the cylinder to be tested 3. remove the air cleaner and oil fill plug 4. rotate the crankshaft to bring the piston in the cylinder to top dead center on the compression stroke • top dead center on the exhaust stroke will result in both the intake and exhaust valves open • always rotate in the running direction 55

Cylinder Leakage Test • Is performed in the following manner: 5. install the tester adapter hose in the spark plug hole 6. verify the regulator is set to zero and connect the air supply • excessive pressure can damage the engine components and seals 7. connect the tester to the tester adapter hose 8. obtain readings per the test manufacturer’s specifications 56

Cylinder Leakage Test Readings • May be unacceptable – in this case, determine where the leak is coming from by listening for hissing air • if the intake valve is leaking, there will be a hissing inside the fuel intake • if air is leaking past the exhaust valve, it will be heard through the muffler • if air is leaking past the piston rings, it should be heard through the oil fill hole or dipstick tube • if there is a blown head gasket, air will be heard escaping in that area 57

Fuel System Inspection • Is a very important part of troubleshooting engines – fuel systems are responsible for a significant amount of failures a technician will encounter Four-Stroke Fact: Always use the manufacturer’s recommended adjustment procedures to ensure maximum power output and to ensure the unit will meet emission compliance. 58

Fuel System Inspection • Is performed in the following manner: 1. inspect the fuel by obtaining a sample from the carburetor for contamination (water, debris, incorrect fluids) • if the fuel is old and starting to turn to varnish, you may notice a skunk-like smell which means the fuel has spoiled, and the fuel system will have to be cleaned or flushed to get the unit to run again 2. check the fuel tank for contamination 3. make sure the fuel filter is installed and not dirty • which could cause a lean operating condition and over-speed at wide open throttle 59

Fuel System Inspection • Is performed in the following manner: 4. check the fuel line for any signs of holes or cracks 5. ensure limiter caps are adjusted at the rich stop (farthest it will open counterclockwise) • if the low-speed mixture needle is set too lean, the engine may bog or hesitate when accelerating from low to high speed; before confirming this problem, verify the engine is thoroughly warmed up or the engine may accelerate poorly 6. examine the fuel system for leaks • check the fuel intake system, hoses and tank for damage; check for fuel on the outside of these components 60

Fuel System Inspection • Is performed in the following manner: 7. using both a pressure and a vacuum test, determine if the fuel tank vent is working correctly • most fuel tank vents are two-way systems • air is let into the tank and fuel is consumed, and air is released when pressures increase inside the tank from expanding fuel vapors • most fuel cap styles and remote tank vents are designed to hold 1. 5 to 5 psi (0. 1 to 0. 3 bar) pressure in the fuel tank • when the fuel tank is pressurized slightly, the boiling point of the fuel rises, which helps prevent vapor lock 61

Fuel System Inspection • Is performed in the following manner: 8. pressure test the fuel tank for leaks • attach the pressure tester to a line going to the fuel tank, block off any return or vent lines and apply 7 psi (0. 5 bar) to the tank • if the tank leaks, locate the leak and correct the problems Four-Stroke Fact: Fuel tank leaks are unacceptable and pose a fire hazard. 62

Fuel System Inspection • Is performed in the following manner: 9. inspect the carburetor and rebuild if possible • if the pressure test of the carburetor fails or contamination is suspected, a carburetor rebuild will be required • if the throttle shaft is worn with up-and-down movement, the carburetor will need to be replaced due to air and dirt being pulled into the engine • carburetors require replacement when a technician sees a worn throttle shaft or rotor, corrosion, extreme varnish inside the carburetor body, bent or grooved adjustment mixture needle, leaking fuel inlet needle seat, or bad main nozzle check valve 63

Exhaust Inspection • Is an important part of troubleshooting engines – a damaged exhaust system can lead to dangerous conditions • Includes examining the following: – muffler – exhaust manifold gasket – catalytic converter – oxygen sensor 64

Exhaust Inspection • Begins with removing all shrouds and shields from the muffler and stacks • Includes checking for the following: – leaks – corrosion – bulges, distortions or cracks – damaged or missing heat studs, fins or other heat sink material 65

Engine Performance • Is important to understand essential to troubleshooting an engine problem properly • May be affected by the following: – engine vibration – engine overheating – engine runs, but stops after a short period – engine misses under load – engine lacks power – engine speed fluctuates – engine hard to restart when warm – oil seal leak 66

Engine Vibration • May be due to: – engine mounts broken or not secure – bent crankshaft – out-of-balance cutting attachment – gear case issues – bent drive shaft 67

Engine Overheating • May be due to: – cooling airflow obstructed – operation with the wrong type and heat range spark plug – lack of proper lubrication – carburetor adjustment – operating the unit with a loose or missing muffler – missing air deflector or heat shield – excessive engine loading – improper ignition timing 68

Engine Runs, but Stops After a Short Period • May be due to: – fuel tank vent problems – carburetor float vent problems – debris in carburetor – excessive engine heat – ignition system defective – insufficient or no engine pulse to fuel the pump – bad fuel 69

Engine Misses Under Load • May be due to: – faulty spark plug • cracked insulator – faulty ignition system – carburetor adjustment – bad fuel 70

Engine Lacks Power • May be due to: – dirty or plugged air cleaner – choke partially closed – excessive engine heat – cylinder head leaking – worn or broken piston rings – exhaust system obstructed • spark screen/exhaust port clogged – throttle not operating fully – low compression – bad fuel 71

Engine Speed Fluctuates • May be due to: – governor linkage adjustment – governor linkage binding – fuel tank vent problem – debris in carburetor – engine air leak 72

Engine Hard to Restart When Warm • May be due to: – excessive engine heat • obstruction cooling airflow – ignition failure – flooded engine – low compression – engine idle speed too low – incorrect fuel • old fuel or vapor lock 73

Oil Seal Leak • May be due to: – oil seal worn or damaged – worn crankcase bearing/bushing – oil seal improperly installed – loss of crankcase vacuum 74

Resources • The Equipment & Engine Training Council Four-Stroke Education Committee (2016) Four-Stroke Study Guide 75

Acknowledgements Assistant Brand Manager Stevi Huffaker Special Thanks The Equipment & Engine Training Council Graphic Designer Melody Rowell Quality Control Director Angela Dehls V. P. of Brand Management Clayton Franklin CEV Multimedia, Ltd. ©MMXVII Executive Producer Gordon W. Davis, Ph. D. 76