71-00-00 Jan 10/90
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
B. Fault Isolation(continued)
CHART 1 FAULT ISOLATION (ENGINE) (Sheet 1 of 3)
Fault
Cause
Enginefailsto start. Nofuelsupplytoengine.
Airinfuelsystem.
Openignitioncircuit.
Defectiveenginedriven
fuelpump.
Defectivefuelcontrol
unit.
Defectivestartingflow
control.
Restrictedfuel
nozzles.
Enginedoesnotidleproperly. Idlespeedsettingincorrect.
Leakor restrictionin
FCUpneumaticsystem.
Remedy
Checkfor cleanfuel supply
at firewallshutoffvalve.
Performmotoringrun.
Checkwiringandconnections
Checkfor flowfrom pump
while motoringengine. If
noflow,replacepump.
Checkforflow from FCU outlettubeto startingflow controlwhile motoring engine.If no flow,remove FCU,checkbypassvalveby applying5 psi max.to bypass returnportandcheckfor air leakagefrom FCUinlet. If leakageisfound, replace fuel controlunitand fuel pump.If no leakage,replace only FCU.
Disconnectprimarytube
andcheckfor evidenceof flow whilemotoringengine with startcontrolleverin
runposition.If noflow, replacestartingflow control.
Cleanandchecknozzles. (Referto EngineMain-tenanceManual.)
Adjustidlespeedandminimu flow as required.
Checkall pneumatictubes andconnectionsfor leakage.
EFFECTIVITY: 040-999
Jan
Jan 10/90
71-0000
71-00-00
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
B. Fault Isolation (continued)
CHART 1 FAULT ISOLATION (ENGINE) (Sheet 2 of 3)
Fault
Enginedoesnot accelerateproperly.
Enginedoes not decelerate.
Enginedoes not developfull power.
Excessivevibration.
Cause
Leak or restrictionin
fuel control pneumatic
system.
P3filterplugged.
Defectivefuel control
unit.
Power control linkage
adjustedincorrectly.
Defectivefuel control
unit.
Faulty engine instru-
mentation.
Controllinkageadjusted
incorrectly.
Propellergovernorpneumatic
sectionadjustedincorrectly.
Leak or restrictionin fuel
controlpneumaticsystem.
Enginepowersettingsnot
adjustedcorrectly.
Defective fuel control unit.
Restrictedfuel nozzles.
Propellerout of balance.
Compressoror compressor
turbinedisc out of balance.
Remedy
Check all connectionsfor
leakage. Check for dirt in P3
meteringorifice. (Referto
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