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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