Piper COMANCHE PA-24-180 Service Manual page 512

PIPER COMANCHE SERVICE MANUAL
2. Late Plunger Pump. (Refer to Figure 8-16.)
a. Detach pump from the aircraft and remove the bottom cover (1), gasket (2) and filter (4).
b.
Remove the retainer spring (5) from the plunger tube ( 1) using dun nose pliers o spread and
remove ends of retainer from tube. Then remove washer (6). "0" ring sel (7). cup valve (8). plunger spnng
(9) and plunger (10) from cube (11).
c.
Wah parts in cleaning solvent and blow out with ir pressure. If plunger does nor wsh clean
or if there are any rough spots gently clean surface with crocus cloth. Slosh the pump asembly in cleaung
solvent. Swab the inside of the tube with a cloth wrapped around a stick and blow out with air pressure.
d.
To reassemble the pump, insert the plunger usembly (10) in the cube with the buffer spring
end first. Check fit by slowly raising and lowering the plunger in the rube. It should move freely without
any tendency to stick. If a dick cannot be
heard, the interrupter asembly us not functioning properly in
which case the pump should be replaced.
e.
To complete the assembly, install the plunger spring (9), cup valve (8), "0" ring seal (7) and
washer (6). Compress spring (9) and assemble retainer (5) with ends of retainer in side holes of cube (11).
Reinstall filter, cover gasket. magnet and cover. Safety and install on aircraft. Check for fuel leakage.
8-27. Resistance Check (Plunger Type Pump). To check the resstance of the pump. connect an ohmmeter
to the lead wire of the pump and the pump body. A reading of 4.87 to 6.4 ohms for a 12 volt pump should
be obtained.
8-28. Servicing Of Fuel Pumps Bendix Model Nos. 480 518-1 480 528 & 480 533.
1. Description and General Information
a.
These are vane type positive displacement pumps, driven by 12 volt DC motors. Each model
has a bult-in pressure relief valve which functions to bvpass fuel, via interal pasages. to the inlet port. The
motor drives the pump through a rubber coupliig. A "live" shaft seal i
in the pump section of the
assemblvy.
b
Field servicing consists of replacing the following pars as required: Cover Gasket (13), Shaft
Seal (12), Coupling (2). Motor Gasket (11) and Motor (1). Refer to Parts Catalog for replacement part
numbers.
c.
If a pump is removed because of fuel leakage. dry the outside of the pump and run the pump
on the bench with test fluid to determine if leakage is from the cover gasket or the shaft seal.
2. Cover Gasket Replacement. (Refer to Figure 8-17.)
a.
Mark the position of the cover with a scribe mark. Remove the eight cover screws (10) and the
cover (9). The spring (8) and pressure plate (7) are now loose and may be set aside. There is no need to
remove any vanes (6), use care to assure that none are lost. Remove the cover gasket ( 13) and all traces of
this gasket from sealing surfaces on the cover and housing assembly (3).
b
Reassemble the pump using a new Cover Gasket (13). The gasket should drop over the
housing insert (4). Note that the spring (8) and pressure plate (7) must be located in their respective
counterbores in the cover (9) as the cover is pulled down by the screws ( 10). Be sure the cover is installed in
its onginal position. (With the cover installed correctly, the cast word "Bendix" on the cover will be on a
diagonal with the "B" nearest the outlet). Torque the cover screws (10) in opposite parts to between 25 and
35 in. Ibs.
3 Motor Replacement.
a.
Remove the two motor nuts (14). the motor (1). the motor gasket ( I) and the coupling (2).
If there is a felt cylinder in the coupling end of the housing assembly. remove this felt cylinder and discard
it.
FUEL SYSTEM
ISSUED: 8/18/72
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