Small Engine Troubleshooting

1. Small Engine Troubleshooting

2. Introduction (Source: Small Engines, R Bruce Radcliff) Troubleshooting: The systematic elimination of the parts of a system or process to locate the malfunctioning part(s).

3. Five keys to trouble shooting • Work systematically. • Never make assumptions. • Isolate the cause of the problems as quickly as possible. • Analyze all affected factors related to the condition. • Remedy the cause of the problem, not just the effect.

4. Four (4) Troubleshooting Steps Investigation Isolation Remedy Documentation

5. Troubleshooting Methods Easy-likely Split half Quick check Systems Sequential

6. Easily-likely • ELM: isolates the cause of a malfunction by grouping possible causes as easy, difficult, likely and unlikely. • Once the possible causes have been grouped the problem is solved is sequence by identifying the easy-likely, easy-unlikely, difficult-likely and difficult-unlikely • Requires good understanding of engine systems and previous experience.

7. Easily-likely –cont. - Example A riding lawn mower was used the previous season and stored for the winter. When the owner attempted to use it in the spring it could be cranked, but would not start. Plugged carburetor No fuel Bad plug Bad coil

8. Split Half Split Half: isolates the cause of a malfunction by splitting the system into parts until the cause is isolated.

9. Split Half – cont. - Example You are mowing grass with a self-propelled mower on a very hot summer day and stop for lunch. When you return the mower will not start. You check and find the tank has gas. What do you do?

10. Split Half – cont. - Example No spark Step one: Check for spark at the spark plug. Good Spark 1. Fuel system 2. Compression system No or weak spark Split electrical system into parts and check each part. Start with easiest. Spark plug

11. Split Half – cont. - Example No spark Step two: Remove spark plug from system. Good Spark Bad spark plug No or weak spark Check another electrical component. Stop switch/wire

12. Split Half – cont. - Example Step three: Remove stop switch from system. No spark Good Spark Bad stop switch No or weak spark Check another electrical component. Flywheel magnets

13. Split Half – cont. - Example Step four: Polish magnet(s). Good Spark Engine runs. No or weak spark Check another electrical component. Ignition coil

14. Split Half – cont. - Example Step five: Remove and test Coil. Note: coil must be tested with a special coil testing machine or with a multi meter. Good coil Check for unique problem such as shorted wire, etc. No or weak spark Replace coil

15. Quick-check • Isolates the cause of a malfunction by focusing on common problems identified by the manufacturer, product history, and/or service experience. • May only be available to service personal.

16. Quick-check – cont. - Example You go home for the weekend and are told that the last time the walk behind mower was being used the blade hit something and the engine died. No one can get it started. Quick check: flywheel key Anyone that works with B & S engine driven lawn mowers know the they use an aluminum flywheel key that is designed to shear when the blade strikes an object. When this occurs the ignition is out of time.

17. Systems approach • Isolates problems by dividing the engine into separate systems and subsystems. • Five (5) common systems. • Compression • Fuel • Electrical • Cooling • Lubrication • Symptom(s) of engine is traced to system and system parts.

18. Sequential method Starts at one end of a system and tests all of the parts, in sequence, until the problem is found.

19. Sequential Method - Example When trying to get an engine to start, your tests indicate the engine is not getting fuel to the combustion chamber. • Trouble shooting sequence. • Fuel tank • Fuel filter • Fuel lines • Carburetor • Intake valve

20. Summary • The successful troubleshooter uses an analytical approach to trace the problem to the engine part or parts that are malfunctioning. • Successful troubleshooters do not rely on any single method discussed in the textbook, but would develop their own system that would be a combination of all of these.