Table 1. 4-Cycle Engine Troubleshooting Chart - Tecumseh VLV Technician's Handbook

Cause
Spark plug fouled.
Improper spark plug gap.
Spark plug porcelain cracked.
Improper valve clearance.
Weak valve spring.
Air cleaner fouled.
Air cleaner fouled.
Lack of lubrication.
Ignition improperly timed.
Valves leaking.
Worn rings.
Cooling fins clogged.
Air flow obstructed.
Fuel tank cap vent hole clogged.
Lack of lubrication.
Excessive load on engine.
Carbon in combustion chamber.
Engine improperly timed.
Governor parts sticking or binding.
Carburetor throttle linkage or throttle
shaft and/or butterfly binding or sticking. Carburetor throttle linkage or throttle
Intermittent spark at spark plug.
Governor not set properly.
Dirty carburetor.
Valves not seated.
Engine not securely mounted.
Bent crankshaft.
Associated equipment out of balance.
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Table 1. 4-Cycle Engine Troubleshooting Chart (Continued)
Engine Misses Under Load
Remedy and Reference
Replace spark plug.
Regap spark plug.
Replace spark plug.
Adjust valve clearance to recommended specifications.
Replace valve spring.
Service air cleaner.
Engine Lacks Power
Service air cleaner.
Fill crankcase to the proper level.
Replace flywheel key.
Grind valves and set to recommended specifications.
Replace rings.
Engine Overheats
Clean cooling fins.
Remove any obstructions from air passages in shrouds.
Open vent hole.
Fill crankcase to proper level.
Check operation of associated equipment. Reduce excessive load.
Remove cylinder head and clean carbon from head and piston.
Replace flywheel key if sheared.
Engine Surges or Runs Unevenly
Clean, and if necessary repair governor parts.
Clean, lubricate, or adjust linkage and deburr throttle shaft or butterfly.
Disconnect ignition cut-off wire at the engine. Crank engine. If spark,
check ignition switch, safety switch and interlock switch. If no spark,
check ignition air gap. Check wires for poor connections, cuts or breaks.
Perform static governor setting.
Clean carburetor.
Clean carbon from valve, recut seats, check valve clearance.
Engine Vibrates Excessively
Tighten loose mounting bolts.
Replace crankshaft.
Check associated equipment.
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