Ignition Description And Operation; Magneto Troubleshooting - Piper PA-44-180 SEMINOLE Maintenance Manual

GENERAL.
DESCRIPTION AND OPERATION.
The magnetos feature two electrically independent ignition circuits in one housing. A single four pole rotor
provides the magnetic energy for both circuits. This magneto uses an impulse coupling to provide reliable
ignition to engine cranking speed. A single cam operates the main breakers for both magneto circuits.
Suppression of contact point arching and conducted radio interference is accomplished by feed-thru capacitors
which are mounted in the magneto cover which forms a part of the magneto harness assembly. At low engine
cranking speeds the impulse coupling automatically retards the magneto until the engine is also at its retard firing
position. The spring action of the impulse coupling is then released to spin the rotating magnet and produce the
spark required to fire the engine. After the engine starts, the impulse coupling flyweights do not engage due to
centrifugal action. The coupling then acts as a straight drive and the magneto fires at the normal firing position of
the engine.
A S C E RTAIN THAT THE PRIMARY CIRCUITS OF BOTH ENGINES ARE
GROUNDED BEFORE WORKING ON THE ENGINE.
Trouble
Failure of engine to start.
Failure of engine to idle
properly.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— CAUTION —
TROUBLESHOOTING.
CHART 7401. TROUBLESHOOTING (MAGNETO)
Cause
Defective spark plugs.
Defective ignition wire.
Defective battery.
Improper operation of
magneto breaker.
Faulty ignition system.
3F18
Remedy
Clean and adjust or replace
spark plugs.
Check with electric tester and
replace defective wires.
Replace with charged battery.
Check points. Check internal
timing of magnetos.
Check entire ignition system.
Page 74-01
Revised: May 15, 1989
7 4 - 0 2 - 0 0