(1.) Prepare metal (refer to sealing metal fitting surfaces).
(2.) Apply 5923C mixed repair cement and cure by either method.

(f)
If patched area of fuel cell lacks repair cement proceed as follows:

(1.) Buff surface next to missing sealant with emery cloth.
(2.) Wash surface three times with MEK.
(3.) Apply four coats of 5923C mixed repair cement.
(4.) Clamp and cure using either method.

EFFECTIVITY: 040-999

28-10-00Jan10/90
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL

A. Distribution
1. Description and Operation
(a) Fuel Valves (refer to 28-20-00 Figure 301)
The PA-42-720 contains three major fuel control valves consisting of two primary fuel shutoff
valves and a crossfeed valve. Each fuel shutoff valve is mounted to a wing forward spar
reinforcementplate within the wing root cavity. The crossfeed valve is mounted to a tee fitting
on the left wing rib in the left root cavity and is connected in line with the left fuel feed line.
(b) Fuel Filter (refer to 28-20-00 Figure 1)
Fuel filters on the PA-42-720, located on the left side of the engine firewall, are reached by
removingthe top engine cowling. Maintenance to filter assembly is limited to removal and
cleaning of filter screen, repair of minor damage or corrosion, or total replacement of filter
assembly.
Bypass Valve Assembly
O-Ring
Element
Fuel Filter Assembly Figure 1

EFFECTIVITY:
040-999
28-20-00PAGE1
Jan 10/90

PIPER AIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. Distribution(continued)
Vent 
Vapor Bleed 
Line 
Sump Drain 
Valve 
Anti Siphon 
Fier Cap 
Nacelle Fuel 
Tank 

Fuel Feed and Crossfeed Installation 
Figure 2 
EFFECTIVITY: 
PAGE 2Jan 10/90 28-20-00  040-999 

PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCE MANUAL

A.  Distribution(continued) Fuel Cell
Check Valve and Connector
VIEW B  VIEW A
Wing Fuel System Figure 3

EFFECTIVITY: 040-999
28-20-00 PAGE3

PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCE MANUAL

A. Distribution(continued)
(c) Fuel Jet Pumps (refer to 28-20-00 Figures 302 and 401)
The PA-42-720 is equipped with a jet scavengerfuel pump which returns unused fuel at start and shut down and a jet transfer fuel pump which transfers fuel from the inboard aft auxiliary tank to the inboard main tank.
The jet scavenger pump (Figure 302) is mounted to the inlet air duct on the right rear side of each engine.
The jet transfer pump (Figure 401) is located in the wing root cavity 8.5 inches in front of the aft sparand clamped to the aft inboard (auxiliary) tank nipple. Though the auxiliary tank is interconnected
with the inboard main tank, the auxiliary tank is the lowest part of the system and requires a means of transferring fuel to an engine feed area once the fuel level has decreasedbelow the interconnecting
tube level. The jet transfer pump draws all fuel from the aft inboard fuel tank to the feed area in the inboard main tank. High pressure filtered fuel is deliveredto the pump, which uses a venturi affect to pull unused fuel from the auxiliary tank and delivers it to the inboard main tank.
2. Fault Isolation -Fuel System
CHART 1 FAULT ISOLATION (FUEL SYSTEM)
Fault  Cause  Remedy 
Fuel valves leak,  Obstructionin inlet side of  Trace lines and locate obstruction. 
pressurelow or  pump. 
pressuresurges. 
Faulty pump.  Replacepump. 
Unidentifiedleak.  Fuel lines damaged or  Locate and repair. 
improperlyinstalled. 
O-ringsimproperlyinstalled.  Locate and repair or tighten. 

EFFECTIVITY:
040-999

Jan 10/9028-20-00
PIPERAIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL

A. Distribution(continued)
3. Overhaul of Fuel Shutoff Valves

NOTE: A kit (P/N 763-995) containing valve for replacement parts can be obtained from Piper.
Disassemblevalveand rebuild as follows:
(a)
Firmly secure valve in vise between two slabs of wood or thick sheets of soft aluminum.

(b)
With screwdriver that fits securely in screw heads, apply small amount of down pressure on screws and remove screws from body. Screws are secured with Loctite Grade A thread lock.

(c)
Remove safety wire and screw in valve shaft. The screw is also secured with Loctite.

(d)
Ensure valve is closed position and remove handle on valve shaft. Note position of valve shaft and roll pins.
　
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