1. Troubleshooting Small Engines by Jason Spurlin 4/10/02 Virginia Tech This presentation has not been edited by the Georgia Curriculum Office.

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 psi for starting and 90 psi during operation

6. Check Easiest Things First
Is there clean, fresh fuel in the tank?
Fuel shouldn’t 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.

7. Eliminate Operating Requirements (Listen to the Engine)
EXAMPLE
Try to start the engine.
If the engine spins but won’t start, eliminate lubrication.
While spinning the engine, check for sufficient compression. If sufficient, eliminate compression.
If engine stalls but doesn’t 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

9. Engine Fails to Start or Start with Difficulty No fuel in tank
Cause
Effect
Engine Fails to Start or Start with Difficulty
No fuel in tank
Obstructed fuel line
Spark plug fouled
Fill tank with fresh fuel
Clean fuel screen and line
Clean and regap spark plug
Engine Misses Under Load
Spark plug porcelain cracked
Faulty condenser
Improper carburetor adjustment
Replace spark plug
Check condenser on a tester and replace if necessary
Adjust carburetor
Engine Overheats
Engine improperly timed
Time engine
Air flow obstructed
Clean shrouds and screens

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

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. Engine Misses under Load
Ignition System
Engine won’t Start
Cause
Remedy
Disconnected spark plug wire
No spark at plug
Spark plug porcelain cracked
Spark plug fouled
Faulty magneto
Sheered flywheel key
Connect wire
check switches and magneto
replace plug
clean and regap
check air gap, if necessary overhaul mag.
replace flywheel key
Engine Misses under Load
Fouled Plug
Porcelain cracked
Improper spark plug gap
Pitted breaker points
Faulty condensor
regap
replace points
check on a tester, replace if necessary

15. Ignition cont. Other ignition problems: rust on iron plates
Engine Lacks Power
Magneto improperly timed
reset air gap
Engine Runs Unevenly
Intermittent spark at plug
check switches, check magneto for loose or damaged wires
Other ignition problems:
rust on iron plates
faulty magnets

16. Armature air gap too large
Disconnected spark plug wire
Burned plug

17. Lubrication System
Insert 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
Fill crankcase to proper level and/or check oil slinger
Drain oil to proper level

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. Broken air fin Clogged air passages
Insert pictures of clogged vanes,, etc

21. Fuel System

22. Fuel System
Fuel system has to deliver clean, fresh, and properly proportioned fuel/air mixture to combustion chamber.
Engine Fails to Start
Cause
Remedy
No fuel in tank
Shut-off valve closed
Obstructed fuel line
Tank cap vent obstructed
Water in fuel
Overchoked
Improper carburetor adjustment
Primer bulb busted
Fill tank
Open valve
Remove and clean fuel line
Open vent
Drain tank and refill with clean fuel
Close shut off valve and pull cord until engine starts
Adjust carburetor
Replace primer bulb

23. Fuel System cont. Engine Misses Under Load
Improper carburetor adjustment
Reed valves stuck
Adjust carburetor
Clean or replace reed
Engine Lacks Power
Choke partially closed
Air cleaner dirty
Reed fouled (2 cycle)
Improper fuel/oil mixture (2 cycle)
Open choke
Clean or replace air filter
Clean or replace
Drain tank; fill with proper mixture
Engine Surges or Runs Unevenly
Fuel tank cap vent hole clogged
Governor parts sticking or binding
Carburetor throttle linkage or throttle shaft binding or sticking
Dirty Carburetor
Open vent hole
Clean and repair if necessary
Clean, lubricate, or adjust linkage
Adjust carb
Clean carburetor

24. Intact Primer Bulb
Clean Air Filter
Clean Carburetor
Fuel Line

25. Most new carburetors do not have needle valves and cannot be adjusted, but many old types are still in operation.

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

28. Burnt valve
Chipped piston
Missing head gasket

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.