Damaged ignition cable All laminated shims Crankshaft counterweight bushings Piston pin plugs
A.C. diaphragm fuel pumps
OVERHAUL MANUAL LYCOMING 76SERIES AIRCRAFT ENGINES Section4
IgnitionSystem
SECTION 4
IGNITION SYSTEM
4-1. General. All four cylinder engines are equipped with high tension ignition systems which deliver high tension current directly to the spark plug outlets.
4-2. Dual Magnetos. The magneto features two electrically independent ignition circuits in one housing. A single four pole rotor provides the magnetic energy for both circuits. The magneto uses an impulse coupling to provide reliable ignition at engine cranking speed. At engine cranking speed the impulse coupling automatically retards the magneto until the engine is also at its retard firing posi-tion. The spring action of the impulse is then released to spin the rotating magnet and produce the spark to fire the engine. After the engine starts, the impulse coupling acts as a straight drive and magneto fires at the normal firing position of the engine.
4-3. Engine Firing Order. Four cylinder engine 1-3-2-4. Left hand rotation engine 1-4-2-3.
4-4. Ignition Harness. The harness is composed of the magneto terminal assembly, the ignition cable and the spark plug end assembly. The number of lead in the harness assembly is of course determined by the number of cylinders on the engine.
4-5. Spark Plugs. For information relative to approved spark plugs for the subject engine consult the latest edi-tion of Service Instruction No. 1042.
1.
Spark Plug
2.
Magneto
3.
Ignition Harness
4.
Nut
5.
Lockwasher
6.
Clamp
REMOVAL AND DISASSEMBLY
4-6. Ignition Harness. Remove the terminals from the topand bottom spark plug. Detach all clips, clamps and grom-met plates securing the leads to the engine. The ignition harness on the dual magneto cannot be removed from the magneto without removing the cover from the magneto.
NOTE
Before detaching clamps, clips, grommet plates etc., mark
the location of each. Differences in various installations make it impossible for this manual to point out the correct attaching points.
4-7 Magneto. Loosen and remove the two 5/16-18 nuts, lockwasher and clamps which hold the magneto to engine. Remove magneto and harness from the engine.
INSPECTION
4-8. Ignition Harness. Unless the harness assembly is in obviously new condition and is known to have been recently installed, it is recommended that the harness be replaced at overhaul.
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