Overhaul Of Fuel Shutoff Valves - Piper Cheyenne IIIA Airplane Maintenance Manual

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
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.
Disassemble valve and 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.
(e) With pliers, remove roll pins.
(f) Pull fitting from valve body and remove O-ring.
(g) Clean fitting and apply Dow Coming Lubricant (FS3451) or equivalent to O-ring flange.
(h) Install new MS29513-019 O-ring. Set fitting in clean area and cover with clear plastic. (Saran
wrap, etc.)
(i) Remove and throw away valve (spring, washer, and spacer.
(j) Remove and dispose seal (2555-05, Dukes) and O-ring.
(k) Remove valve from vise. With soft, wood dowel, push out ball from other end of valve body.
Be careful not to nick or damage ball. Clean as necessary.
(I) With roll pin removed from shaft, push control shaft into valve body and remove.
(m) Remove O-ring from shaft and clean O-ring.
(n) Remove other seal, O-ring, wave washer, and spacer.
(o) Thoroughly clean inside of valve and dry.
(p) Install new valve washer and spacer.
(q) Using Dow Coming Lubricant (FS3451) or equivalent, lubricate one 2559-05 seal and install
MS29513-016 O-ring on seal.
(r) Carefully insert seal in body until it meets spacer.
(s) With control shaft clean and corrosion free, lubricate with Dow Coming Lubricant (FS3451) or
equivalent. Install MS29513-008 O-ring.
(t) Apply large amount of lubricant on bottom of shaft (28-20-00 Figure 301) and install shaft in
valve body.
(u) Replace roll pins so shaft pin is positioned on side with open designation. Install grooved pins
in body with grooved ends down.
(v) With shaft in closed position, install handle.
(w) Coat AN500AD6-3 screw threads with threadlock from kit. Install two AN960C6L washers and
screw on shaft. Safety wire handle and screw.
(x) Install ball valve, ensuring ball slides into body with openings toward side of body. Also ensure
shaft flange is snug against body flange (28-20-00 Figure 301).
(y) Install second seal per steps (q) and (r) above.
(z) Install other new spacer and washer.
(aa) With fitting prepared per steps (g) and (h), install it on valve body with attaching screws,
ensuring threads are coated with Loctite.
EFFECTIVITY:
28-20-00
PAGE 5
Jan 10/90