A. Distribution (continued)
NOTE: Pump pressure 33+/-1 psi at 80% rpm and 300 pounds/hour flow rate.
To Tee on Fuel Oil Heater
Accessory Pad H on Engine Adjust Fuel Pressure Here
Dual Drive Support Bracket DualDrive AdapterAssembly Pump
To Fuel Filter
Main Fuel Supply Pump
Figure 301
EFFECTIVITY:
040-999 Jan 10/90
Jan 10/90 73-10-0073-10-00
PIPER AIRCRAFT PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. Distribution (continued)
Fuel Pump Drive Shaft
Preformed
Packing
Discharge
Filter
Element
Preformed
Packing Inlet Filter Cover
Inlet Filter
Element
Preformed
Packing
Discharge Preformed
Filter Packing
Cover
FuelControl Unit Fuel Pump
Figure 302
EFFECTIVITY:
040-999
3
73-10-00 PAGE
73 -10-00 Jan10/90
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. Distribution (continued)
LineConnectorto
SolenoidValve
Hose to Fuel
Divider
Spring Clamp ModifiedElbow
O-Ring
OverflowDrain Line AN924-4 Nut SpringWasher
Jet
Nozzle
Fuel Scavenge Can
O-Ring Seal
Fuel Overflow Check Valve
Drain
Jet Scavenge Pump
Figure 303
EFFECTIVITY:
PAGE4 73-10-00 040-999
Jan 10/90
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCE MANUAL
A. Distribution (continued)
5. Fuel Scavenge System (Figure 303)
The purpose of the fuel scavenge system is to collect residual fuel after engine shutdown, and returnfuel to nacelle fuel tank during engine start. The system consists of a solenoid valve, a jet type pump with an integral reservoir mounted on the side of the oil cooler duct below the accessory gearbox housing, a check valve at the pump outlet, and the necessary lines and tubing interconnecting the system.
The system operates during engine shutdown and startup only. When engine is shutdown, residual fuel is drained into scavenge pump reservoir from fuel nozzles. During engine startup, a solenoid valve is energized, allowingengine purge fuel to enter the scavenge pump jet. The high velocity fuel from the jet picks up the fuel in reservoir and returns fuel to nacelle tank. When starter is released, the solenoid valve is returned to the closed position. An overboard vent line is attached to scavenge pump in the event of a malfunction. The presence of fuel being vented overboardindicates system is not operating properly. Maintenance to system is limited to checking solenoidvalve for proper operation and examining lines and tubing for obstructions or leakage.
(For maintenance information, refer to 28-20-00.)
CHART 1 FAULT ISOLATION (FUEL SCAVENGE SYSTEM)
Fault Cause Remedy
Fuel beingdrained Defective check valve. Replacecheckvalve.
overboard during
engine start. Restricted jet pump Remove nozzle and clean.
nozzle. Checkfor proper seating
of jet.
Fuel being drained Solenoidvalve not Checkoperationand
overboardduring opening. replaceif necessary.
engine shutdown.
Restrictedjet pump nozzle. Removenozzleand clean.
Check for proper seating of
jet.
Fuelbeingdrained Defectivecheck valve. Replacecheckvalve.
overboardwith full
tip tanks.
EFFECTIVITY:
040999 73-10-00JanJan10/9010/90
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. Controlling
1.
Preparation of Fuel Control Unit for Service -Off Engine
NOTE: Refer to Pratt and Whitney Maintenance Manual p/n 3034342, Chapter 73, for Preparation of Fuel Control Unit For Service -Off Engine.
2.
Preparationof Fuel Control Unit for Service -On Engine
NOTE: Refer to Pratt and Whitney Maintenance Manual p/n 3034342, Chapter 73, for Preparation of Fuel Control Unit For Service -On Engine.
3.
Preparation for Shipping
Preserve and package fuel control units as follows:
NOTE: Do not permit fuel or oil to enter drive body cavity or air pressure ports.
(a)
Drain all residual fuel from control fuel section. Completely fill with clean oil, conforming to SpecificationMIL-O-6081, Grade 1010. Tip control unit assuring complete film on all parts and passagesin fuel section.
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