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Troubleshooting Small Engines by Mr. Gerbitz 12-17-07

Interest Approach. Bring in a push mower that will not crank and have students try to crank it.Ask the students if they have ever experienced this frustration at home and if they were able to fix the problem.Tell students that we are are going to spend time identifying and fixing problems for the

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Troubleshooting Small Engines by Mr. Gerbitz 12-17-07

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    1. Troubleshooting Small Engines by Mr. Gerbitz 12-17-07

    2. Interest Approach Bring in a push mower that will not crank and have students try to crank it. Ask the students if they have ever experienced this frustration at home and if they were able to fix the problem. Tell students that we are are going to spend time identifying and fixing problems for the next few days.

    3. Systematic Troubleshooting PERFORMANCE OBJECTIVE On a unit test, describe systematic troubleshooting on small engines with at least 70% accuracy. ENABLING OBECTIVES Explain the principles of systematic troubleshooting. Identify the fundamental operating requirements of small engines. Use service manuals and troubleshooting guides to locate tolerances, clearances, and specifications.

    4. Systematic Troubleshooting System of testing one component after another until the problem is located and repaired. BASIC PRINCIPLES 1. Look for the easiest things first. 2. Verify the five fundamental operating requirements. 3. Write down what you have done

    5. Fundamental Operating Requirements Proper Carburetion correct proportion of clean, fresh fuel has to mix with combustion air Correctly operating ignition system strong ignition spark must be timed properly Adequate Lubrication correct amount of clean oil must coat engine components Sufficient cooling air that reaches engine should be less than 20oF hotter than ambient air. Proper compression at least 30-45 psi for starting and 90 psi during operation

    6. Check Easiest Things First Is there clean, fresh fuel in the tank? Fuel shouldnt be more than 1 month old Is the spark plug wire connected? Is the oil level correct? Gather pertinent information from the owner. How was the engine acting before it stalled? Did it start back? If so, how long before it did? Did you hit an obstruction during operation? Put pictures of fouled plugs, valves, dirty engines etc.Put pictures of fouled plugs, valves, dirty engines etc.

    7. Eliminate Operating Requirements (Listen to the Engine) EXAMPLE Try to start the engine. If the engine spins but wont start, eliminate lubrication. While spinning the engine, check for sufficient compression. If sufficient, eliminate compression. If engine stalls but doesnt restart after it cools, eliminate cooling system. Now you can focus on carburetion and ignition. Once you have eliminated as many systems as possible, refer to a troubleshooting guides and service manuals to pinpoint and solve the problem.

    8. Troubleshooting Guides Tables that have common problems, causes, and remedies listed in an easy to read format Example information in a troubleshooting guide: INSERT TROUBLESHOOTING GUIDE INSERT TROUBLESHOOTING GUIDE

    10. Service Manuals Service manuals are engine specific Include service procedures and most common problems Show exploded views of components that help during reassembly Provide charts that list proper tolerances, clearances, and specifications

    11. Insert example of exploded view Insert example of exploded view

    12. Summary Troubleshooting is a process of elimination Check easiest things first. Is fuel in tank? Is spark plug wire connected Ask owner how the engine is performing Verify the 5 fundamental operating requirements: carburetion, ignition, lubrication, cooling, compression. Use troubleshooting guides to locate problem. Use service manuals to locate tolerances, clearances, and specifications. Write everything down that you check.

    13. Troubleshooting Engine Systems PERFORMANCE OBJECTIVE On a lab project, perform systematic troubleshooting of the electrical, lubrication, cooling, fuel, and compression systems with at least 70% accuracy. ENABLING OBJECTIVES Identify symptoms of malfunctioning system components. Inspect spark plug, flywheel key, and magneto. Inspect and repair components of lubricating system. Inspect, clean, and repair cooling fins, flywheel, and air shroud. Inspect fuel tank, fuel pump, carburetor, reed valves (in two-cycles), fuel lines, filters, and air cleaner. Inspect governor and adjust if necessary. Identify and repair causes of poor compression.

    14. Ignition System

    15. Ignition cont.

    17. Lubrication System Insert picture of oil and of oilslingerInsert picture of oil and of oilslinger

    18. Lubrication System Lack of Lubrication Causes: Engine to miss under load Lack of power Overheating Engine uses excessive oil oil level too high oil filler cap loose of gasket damaged > replace gasket oil passages obstructed > clean oil passages

    19. Cooling System A malfunctioning cooling system will cause the engine to overheat When checking cooling system look for: obstructed air flow clogged cooling fins broken cooling fins broken flywheel vanes damaged or removed shroud low oil level

    20. Insert pictures of clogged vanes,, etcInsert pictures of clogged vanes,, etc

    21. Fuel System

    22. Fuel System

    23. Fuel System cont.

    26. Compression System

    27. Compression System The following are symptoms of poor compression. Engine will not start Engine knocks Engine misses under load Engine lacks power Engine uses excessive oil Common causes of poor compression. Damaged or removed crankcase gaskets Carbon deposits in combustion chamber Weak valve springs Leaking valves Cracked porcelain on spark plug Excessive cylinder and piston wear

    29. Checking Compression An engine with proper compression will have a degree of resistance when the operator pulls on the starter rope Use a compression tester 30-45 psi min. for starting 90 psi min. for efficient operation

    30. Other Ailments Clogged exhaust system Insects frequently build nests in exhaust pipes Associated equipment malfunctioning

    31. Summary Once you have checked the easy things, work through the each system until you find the problem Faulty ignition systems can be eliminated if there is spark at the plug. If not, focus attention on magneto, connecting wires, plug, and the flywheel magnets. A faulty cooling system will cause the engine to overheat and stall, but cooling problems can be easily alleviated by making sure air passages and cooling fins are clean and intact.

    32. Summary cont. The fuel system has to allow a CLEAN, proper fuel/air mixture to reach the combustion chamber. Make sure that fuel lines and filters are clear and that the carburetor is adjusted properly. Poor compression is easily identified by resistance when rope starting and by using a compression tester. Problems are generally associated with leaky gaskets, leaking valves, and excessive cylinder wear. Clogged exhaust systems also prohibit an engine from running properly. REMEMBER: Check off each thing that you have checked and/or repaired.

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