WARNING: RESIDUAL VOLTAGE IN THE EXCITER CAN BE VERY HIGH. ENSURE IGNITION IS OFF AND SYSTEM IS INOPERATIVE FOR AT LEAST SIX MINUTESBEFORE REMOVING COMPONENTS. ALWAYSUSE INSULATED TOOLSAND REMOVE COUPLINGNUTS AT EXCITER END FIRST. DO NOT TOUCHOUTPUT CONNECTORS OR COUPLING NUTS WITH BARE HANDS.
(a)
Removepower from ignition system.
(b)
Disconnectpower supply cable from exciter box input connector.
CAUTION: DO NOT ALLOW IGNITION CABLE BRAIDING OR FERRULES TO ROTATE WHEN REMOVING COUPLINGNUTS.
(c)
Disconnecttwo ignition cable couplings from output connectors on exciter.
(d)
Removefour bolts, washers, and self-locking nuts securing unit to bracket.
(e)
Removeignition exciter unit.
(f)
Install replacement unit to firewall with hardware removedin step (d).
(g)
Lightlycoat threads of exciter connectors with fluorocarbon spray lubricant.
CAUTION: DO NOT ALLOW IGNITION CABLE BRAIDING OR FERRULES TO ROTATE WHEN SCREWING ON COUPLING NUTS.
(h)
Connectcouplingnutsof supply cable and two ignition cables to proper connectors on exciter.
(i)
Tightencoupling nuts finger tight, plus 45 degrees; safety with lockwire.
EFFECTIVITY:
040-999 Page1
74-10-00Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. ElectricalPower Supply (continued)
2. CheckingIgnition System
A common ignition problem is a low battery. Before inspecting ignition system, start engine with an auxiliary power unit. If engine does not start, proceed with ignition system check.
During following procedure, an auxiliary power unit for dry motoring runs can eliminate possibility of low voltage at exciter box and excessive battery drain.
WARNING: RESIDUAL VOLTAGE IN THE EXCITER CAN BE VERY HIGH. ENSURE IGNITION IS OFF AND SYSTEM IS INOPERATIVE FOR AT LEAST 6 MINUTES BEFORE REMOVING COMPONENTS. ALWAYS USE INSULATED TOOLS AND REMOVE COUPLING NUTS AT EXCITER END FIRST. DO NOT TOUCH OUTPUT CONNECTORS OR COUPLING NUTS WITH BARE HANDS.
CAUTION: PERFORM DRY MOTORING RUN PRIOR TO SWITCHING IGNITION ON TO ENSURE NO FUEL REMAINS IN GAS GENERATOR CASE. (REFER TO DRY MOTORING RUN THIS SECTION.)
(a)
Switch ignition system OFF.
(b)
Disconnect coupling nut of one ignition cable from output connector on exciter box.
(c)
Switchbattery master and ignition switches ON. Advance CONDITION lever to RUN.
(d)
At gas generator case, listen for snapping sound with frequency of approximately one snap per second. If snapping is audible, ignition is satisfactory.
(e)
Secure engine by moving CONDITION lever to STOP position. Switch ignition and battery master switches OFF.
(f)
Reconnect coupling nut of ignition cable to exciter box. Remove other cable coupling nut and repeatsteps(c) thru (e).
(g)
If snapping sound is not heard after one check, replace proper spark igniter or ignition cable. Repeat steps (c) thru (e).
(h)
If no snapping sound is heard on either check, replace ignition exciter box and repeat steps (c) thru (e).
3. Dry Motoring Run
start and checks for fuel system leaks after component replacement.
An engine dry motoring run clears engine of trapped fuel or vapors after an unsatisfactory
(a)Set power control lever at IDLE.
(b)Set starting control lever at CUTOFF.
(c) Set master switch ON to supply electrical power to starter.
(d)Fuel shutoff valve ON.
(e)Setfuel boost pump switch ON to provide lubricationfor engine driven fuel pumping elements.
(f) Leave ignition switch OFF.
CAUTION: DO NOT EXCEED STARTER TIME LIMITS. (30 SECONDS ON, 1 MINUTE OFF, 30 SECONDS ON, 1 MINUTE OFF, 30 SECONDS ON, 30 MINUTES OFF.)
(g)Operate starter for 10 to 20 seconds.
(h)
Releaseengine starter switch.
(i)
Set fuel boost pump switch OFF after Ng has stopped.
(j)
Set master switch OFF.
EFFECTIVITY:
040-999
Jan 10/90 74-10-00
Jan 10/90 74-10-00
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. Distribution
1. IgniterPlugs
The sparkignitersare locatedat 4 and9 o'clockpositionson gasgeneratorcase,adjacentto fuel manifold.
Observeall safetyprecautionswhenworkingon ignitionsystem.
(a) Removalof IgniterPlug
WARNING: RESIDUALVOLTAGEIN THEEXCITERCANBEVERYHIGH. ENSURE IGNITIONIS OFFANDSYSTEMIS INOPERATIVEFORATLEAST6 MINUTESBEFOREREMOVINGCOMPONENTS.ALWAYSUSE INSULATEDTOOLS. REMOVECOUPLINGNUTSATEXCITEREND FIRST. DO NOTTOUCHOUTPUTCONNECTORSOR COUPLINGNUTS WITHBAREHANDS.
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