Air Operated Pump

TM 55-4940-353-13&P

a. Given clean operating conditions, this unit will

5. Inspect check valve seating surfaces for

be trouble-free. Contaminants from dirty oil may collect

nicks, burrs or excessive wear.

on the siphon tube filter, requiring the filter to be washed

in kerosene and blown off with an air blow gun.

6. Inspect check valves, spring, poppet and

body bore for excessive wear or burrs.

b. If The Oil Delivery Rate Drops -the lubricator

should be cleaned. Shut off the air supply and reduce

7. Inspect air valve for excessive wear caused

the pressure in the unit to zero. Remove the adjusting

by detonate pins.

screw and clean the needle and the seat in the body.

Inspect and clean the passage from the needle seat

b. Assembly. Before starting reassemble

down into the siphon tube adaptor. Remove the

operations, wash all metallic parts thoroughly in solvent

variable orifice screw and clean its air passage with a

similar to Federal Specification PD-680. Lubricate O-

small wire. Check the bore that the screw fits into for

rings, backup rings and threads with hydraulic fluid, or

contaminants and clean if necessary. Be sure the

petrolatum, Federal Specification VV-P-236. Proceed

passageway from the sight dome cavity downward is

with assembly in the reverse of Index Numbers on

open.

Illustration (Figure 4-5).

c. Drain off any contaminants which collect in the

1. Install inlet and outlet check valves (37 &

bottom of the bowl.

38). Do not tighten check valves excessively to

preclude damaging O-ring.

4-5.

Air Operated Pump. If a Air Operated Pump

2. Remove the piston from the body (31).

malfunctions, refer to figure 4-5 and disassemble the

pump following the index numbers in figure 4-5. Then

3. Assemble the drive piston (25) to the driven

take the following steps:

piston by threading it onto the threaded end of the

driven piston until the shoulder on the driven piston

a. Inspection after Disassembly

bottoms in the drive piston counterbore. Install check

nut (23) on the projecting threads of the driven piston

1. Under a strong light and preferably under

and tighten down against the drive piston.

magnification, visually inspect all applicable parts for

cracks, pitting, scoring, and corrosion.

4. Install shifting nut (24) and shakeproof

washer (8) on one end of connecting rod (22) with the

2. Inspect all threads for chipped, crossed, or

top of the nut facing toward the center of the connecting

stripped threads.

rod. Screw nut (24) all the way up the connecting rod,

covering all the threads.

3. Roll springs over a flat surface to check for

wobble.

5. Thread connecting rod (22) into the drive-

driven piston subassembly until nut (24) bottoms against

4. Inspect all tubing for kinks, breaks, or

the face of check nut (23).

defective flares.

4-2