LYCOMING OPERATOR’S MANUAL SECTION 6
O-235 AND O-290 SERIES TROUBLE-SHOOTING
SECTION 6
TROUBLE-SHOOTING
General – Experience has proven the best method of “trouble-shooting” is to decide on the various possible
causes of a given trouble and then to eliminate these causes one by one, beginning with the most probable.
The following chart lists some of the more common engine troubles usually found in maintaining aircraft
engines.
TROUBLE PROBABLE CAUSE REMEDY
Failure of Engine to Start Lack of fuel. Check fuel system for leaks. Fill
fuel tank. Clean dirty lines,
strainers or fuel cocks.
Underpriming. Prime with engine priming
system.
Overpriming. Open throttle and “unload”
engine.
Incorrect throttle setting. Set at ¼ position.
Defective spark plugs. Clean and adjust or replace spark
plug or plugs.
Defective battery. Replace with charged battery.
Improper operation of magneto
breaker points.
Clean points. Check internal
timing of magnetos.
Water in carburetor. Drain carburetor and fuel lines.
Internal failure. Check oil sump strainer for metal
particles. If found, complete
overhaul of engine is indicated.
Failure of Engine to Idle Properly Incorrect carburetor idle
adjustment.
Adjust throttle stop to obtain
correct idle.
Idle mixture. Adjust mixture.
Leak in the induction system. Tighten all connections in
induction system. Replace any
parts that are defective.
Low cylinder compression. Check condition of piston rings,
and valves.
Insufficient spark. Check entire ignition system.
6-1
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